Dawn

- from Chief Engineer/ Mission Director, Marc Rayman (JPL)

November 1, 2018 — Dawn's Long and Successful Mission Concludes

Dawn depleted its hydrazine propellant on Oct. 31, exploring dwarf planet Ceres to the very end. Without the hydrazine, the ship cannot control its orientation in space, so it can no longer point its solar arrays at the Sun to generate electrical power nor its antenna to Earth. The indication that the mission had concluded was the loss of the spacecraft's radio signal at the Deep Space Network (DSN). Mission controllers and the DSN continued to search in order to eliminate other possible explanations.

Dawn performed superbly to the end of its mission and lasted longer than anticipated.

Additional information is in this news release. The depletion of hydrazine had been predicted for quite some time, and the two August Dawn Journals describe still more about the end of the mission and the long-term fate of this remarkable spacecraft.

Thank you for reading the mission status reports. For at least the next couple of decades, and probably much longer, Dawn's status is that this former interplanetary ambassador from Earth is an inert celestial monument to the power of human ingenuity, creativity, and curiosity in orbit around one of the alien worlds it unveiled, a lasting reminder that our passion for bold adventures and our noble aspirations to know the cosmos can take us very, very far beyond the confines of our humble home.

October 30, 2018 — Dawn Operating Smoothly as the End of the Mission Nears

Dawn is operating perfectly as it orbits Ceres. Every 27 hours its orbit carries it down to only 22 miles (35 kilometers) above the dwarf planet, providing the explorer an excellent vantage point for conducting high resolution measurements.

As we have been predicting for months, Dawn will deplete its supply of hydrazine propellant any day now. When it does, the spaceship will lose the ability to orient itself, so it will not be able to point its solar arrays at the Sun or its antenna at Earth. We described in the Aug. 21 Dawn Journal that this was most likely to occur between the middle of September and middle of October, but that it could be earlier or later. (The May Dawn Journal explained the reasons for the uncertainty in the exact data.) Now we can conclude with high confidence that the end will be later than that window! We still expect it to be very soon, but in the meantime, Dawn remains fully healthy.

October 9, 2018 — Dawn Healthy, Productive and Almost Finished

Dawn is continuing to explore Ceres. In this final phase of the mission, it dives down to just 22 miles (35 kilometers) above the alien terrain every 27 hours and acquires a wealth of data. The spacecraft has been executing all of its assignments perfectly.

Any day now, Dawn will exhaust the last of its hydrazine propellant, which is essential for controlling its orientation. The two August Dawn Journals describe how this will end the mission. The September Dawn Journal, recognizing the 11th anniversary of the spaceship's setting sail on the cosmic oceans, provides an annual round-up of some aspects of this grand adventure of discovery.

August 30, 2018 — Dawn Continues Exploring Ceres Even as Mission End Approaches

Dawn is operating flawlessly at Ceres as it continues to acquire high-resolution data. In its final orbit of the mission, the spacecraft performs its measurements as it streaks only about 22 miles (35 kilometers) above the ground, then soars up to 2,500 miles (4,000 kilometers) and plunges back down again. Each loop takes 27 hours.

Dawn relies on hydrazine propellant to control its orientation in the zero-gravity of spaceflight. The explorer will continue operating until the last of the hydrazine is spent, most likely in September or October. It will struggle briefly, but the long and successful mission will be at its end. A pair of Dawn Journals in August describe what will happen to the spacecraft, both right away and for decades to come, as well as the feelings that one member of the team (yours truly) may experience when this extraordinary extraterrestrial expedition concludes.

August 9, 2018 — Dawn Scrutinizing Ceres from Low Altitude

Dawn is continuing its work in the final orbit of its mission. Once every 27 hours, the spacecraft swoops down to about 22 miles (35 kilometers) above Ceres and collects valuable scientific data with a suite of sensors. You can see some of the fabulous views here.

As illustrated in the March Dawn Journal, the low point of Dawn's elliptical orbit gradually shifts south, allowing the spacecraft to investigate different areas as its mission progresses.

July 13, 2018 — Dawn Operating Smoothly in Ceres Orbit

Dawn is performing all of its assignments in its elliptical orbit, dipping down to about 22 miles (35 kilometers) above the ground every 27 hours. Here are some of the high-resolution pictures Dawn has taken.

In June, the spacecraft turned frequently between pointing its scientific instruments at the dwarf planet and pointing its main antenna to Earth. As explained in the most recent Dawn Journal, now Dawn observes Ceres at low altitude for five orbits in a row. It transmits its findings to Earth on the sixth.

June 28, 2018 — Dawn Continuing to Scrutinize Ceres After Last Ion Thrusting of the Mission

Dawn fired its ion engine twice last week to shift the longitude slightly of its south-to-north low altitude flight over dwarf planet Ceres. The pair of maneuvers allowed the spacecraft's sensors to view different areas within Occator Crater. (Recent Dawn Journals describe the nature of this highly elongated elliptical orbit and Dawn's photography and other measurements.)

Now that Dawn is in its final orbit around Ceres, there are no further plans to use the ion engines. For more on this, see this status report. (The next Dawn Journal will have further details.)

The probe flies as low as 22 miles (35 kilometers). Prior to this month, Dawn's lowest altitude was 240 miles (385 kilometers). You can see exquisite pictures here, revealing amazing new details of the alien landscapes.

June 21, 2018 — Dawn Adjusting its Orbit

Dawn is continuing to operate flawlessly in its final orbit of the mission, dipping down to about 22 miles (35 kilometers) above dwarf planet Ceres every 27 hours. Recent Dawn Journals explain more about this elliptical orbit and how the spacecraft operates in it.

Dawn is firing its ion engine twice this week to make a small adjustment in the orbit to optimize its scientific measurements.

June 13, 2018 — Dawn Returning Pictures and Other Data in Lowest Orbit

Dawn completed ion thrusting on schedule on June 6, reaching its final orbit. The spacecraft's elliptical path now takes it around Ceres once every 27 hours, ranging in altitude from about 22 miles (35 kilometers) to 2,500 miles (4,000 kilometers). The explorer's lowest altitude before last week was 240 miles (385 kilometers).

Dawn began observing Ceres on schedule on June 9. Exquisite pictures showing greater detail than ever before are posted in the image gallery. (If you don't look, you'll miss out on stunning new views of Ceres.) The March and April Dawn Journals describe some of the challenges of photographing the dwarf planet when traveling at low altitude and high speed.

The May Dawn Journal summarizes some of the accomplishments last month and begins looking ahead to the end of this extraordinary mission.

June 5, 2018 — Dawn Making Good Progress to New Orbit

Dawn is continuing to use its ion engine to gradually shrink its elliptical orbit around Ceres. Ion thrusting started on May 31 and is scheduled to end on June 6. The targeted final orbit will range in altitude from about 22 miles (35 kilometers) to 2,500 miles (4,000 kilometers).

As Dawn thrust yesterday, its smooth orbital path took it briefly down to an altitude of about 75 miles (125 kilometers), the closest it has yet been to Ceres. Also, as the spacecraft maneuvers lower, it takes less time to complete each orbit. In the science orbit it left last week, one revolution required 37 hours. Today it takes about 28 hours for each loop around the dwarf planet. After thrusting concludes in the new orbit, it will take Dawn just over 27 hours for each revolution, as we explained in the April Dawn Journal.

May 31, 2018 — Dawn Completes Observations and Begins Ion Thrusting

Dawn successfully completed all of its planned observations of Ceres in its latest orbital phase. (See the March Dawn Journal for an overview.)

After transmitting its data to distant Earth, the spacecraft began using ion engine #2 to lower its orbit again. Since arriving in its most recent orbit on May 14, Dawn's altitude has varied smoothly from 280 miles (450 kilometers) up to 2,900 miles (4,700 kilometers). When ion thrusting concludes next week, the orbital altitude will range from about 22 miles (35 kilometers) to 2,500 miles (4,000 kilometers). (See the March Dawn Journal for an illustration of the orbits.)

May 23, 2018 — Dawn Spacecraft Performing Flawlessly in New Orbit

Dawn is carrying out its latest campaign of Ceres observations flawlessly. The March Dawn Journal described the plans for this new phase of the mission.

The explorer has completed five of the ten planned revolutions of photography and spectroscopy. Each elliptical orbit around the dwarf planet takes one and a half days as the altitude ranges from about 280 miles (450 kilometers) up to 2,900 miles (4,700 kilometers). (The small difference between this minimum altitude and the one in the previous mission status report is a result of a refinement in how we present the orbital information in a nontechnical way. The orbit is exactly what mission controllers designed.)

May 15, 2018 — Dawn Ready for New Ceres Observations

Yesterday Dawn completed one month of maneuvering with its ion engine to a new orbit around dwarf planet Ceres. Now in extended mission orbit 6 (XMO6), Dawn will take pictures as well as infrared and visible spectra starting today. The March Dawn Journal described the plans for this new phase of the mission.

Dawn was aiming for an elliptical orbit that ranged in altitude from 270 miles (440 kilometers) to 2,900 miles (4,700 kilometers), and measurements of the orbit parameters by Dawn's navigation team after thrusting completed confirmed that the spaceship is right on target.

May 10, 2018 — Dawn Flying Closer to Ceres

Dawn is continuing to fire its ion engine to reduce its altitude above Ceres. The spacecraft has now decreased the size of its elliptical orbit so much that on May 8, it dipped down to less than 560 miles (900 kilometers) above the dwarf planet. The last time it was that close to the ground was in September 2016.

Dawn started today at an altitude of nearly 3,500 miles (5,600 kilometers). Tonight it will reach down to 450 miles (720 kilometers) before it begins sailing up again. It now takes the ship less than two days to complete one revolution around the dwarf planet. The April Dawn Journalshows Dawn's spiral descent.

May 4, 2018 — Dawn Pauses Thrusting for an Update

Dawn's spiral descent to a new orbit is going smoothly. (The April Dawn Journal includes an illustration of Dawn's descent profile.) Today the spacecraft is scheduled to pause ion thrusting and point its main antenna to Earth. Controllers will radio the spacecraft a routine update to its flight plan, which will cover the next week of ion thrusting.

Today Dawn's shrinking elliptical orbit carries it from 2,000 miles (3,200 kilometers) up to 4,300 miles (6,900 kilometers). Whereas the peak altitude presented in the April 26 mission status update was 7,300 miles (11,800 kilometers), the next orbital crest, which occurs early tomorrow morning, will be 4,300 miles (7,000 kilometers). It now takes the probe only three days to complete one revolution around Ceres, or one-tenth of what it was before ion thrusting began on April 16.

April 26, 2018 — Ion Thrusting Contracts Dawn's Orbit

Dawn is continuing to thrust with its ion propulsion system to lower its orbit around Ceres in preparation for taking new pictures and conducting other scientific observations next month. (The March Dawn Journal has an overview of the plan.) As explained in the April 17 mission status, this maneuvering makes each peak in the spacecraft's elliptical orbit lower than the one before. And in the April 5 mission status, we saw that the elliptical orbit reached 24,300 miles (31,900 kilometers) before ion thrusting began. Today Dawn will sail up to a peak again, but now it will be only 7,300 miles (11,800 kilometers).

As Dawn's orbit shrinks, it takes less time to complete each revolution. Prior to thrusting, Dawn looped around the dwarf planet once every 30 days. Now it takes less than a week, and as thrusting continues, the orbit period will get even shorter.

April 17, 2018 — Dawn Maneuvering to Lower Orbit

Dawn is flying to a lower altitude over Ceres. Under the gentle thrust of ion engine #2, the spacecraft is gradually reshaping its orbit around the dwarf planet. It will take a month to maneuver to the new orbit, designated extended mission orbit 6 (XMO6). Last month's Dawn Journal gives an overview of the plans.

Today Dawn will descend from 16,900 miles (27,300 kilometers) to 15,200 miles (24,400 kilometers).

Although the new orbit will be lower than the previous orbit, Dawn continues to follow an elliptical path around Ceres. The ion thrusting will gradually shrink that ellipse. As a result, most of the time Dawn will get closer to Ceres but sometimes it will ascend, although to a lower peak altitude each time. This will become more apparent as we track the altitude in upcoming mission status reports.

April 12, 2018 — Dawn About to Fly Lower

Mission controllers are putting the finishing touches on the instructions Dawn will follow to fly to a new orbit. Ion thrusting will begin next week. It will require about a month to descend so the probe can undertake new observations, as described in the most recent Dawn Journal.

As it turns out, Dawn is already descending today, but that is for a different reason. The spacecraft is continuing in its elliptical orbit. It reached the high point on April 7. Over the course of the day today, Dawn's altitude will decrease from 22,700 miles (36,500 kilometers) to 21,900 miles (35,300 kilometers).

Tomorrow, Dawn will celebrate its 3,000th Cerean day in orbit around the dwarf planet. The adventurer arrived in orbit in 2015 (an unprecedented and exciting accomplishment that was described here). Ceres turns on its axis in 9 hours, 4 minutes (one Cerean day), considerably faster than Earth, although not all that different from the giant planet Jupiter, which takes 9 hours, 56 minutes.

April 5, 2018 — Dawn Approaching Orbital Summit

Dawn's 30-day elliptical orbit is carrying it to its highest point above Ceres. Just as a ball thrown upward gradually slows before falling downward, the spacecraft is decelerating under the constant pull of the dwarf planet's gravity. Orbiting at an average altitude today of 24,000 miles (38,700 kilometers), the spacecraft is ascending at only 11 mph (18 kph). On April 7, it will reach the crest of its orbit, 24,300 miles (39,100 kilometers) high.

Meanwhile, the mission control team at JPL is continuing to prepare for piloting Dawn to a new orbit for new observations, as described in the most recent Dawn Journal.

March 29, 2018 — Dawn Sailing Upward on Noteworthy Anniversary

As Dawn follows its elliptical orbit around Ceres, it is sailing higher. Over the course of the day today, it will climb from 11,300 miles (18,200 kilometers) to 12,100 miles (19,600 kilometers). As the latest Dawn Journal explains, the spacecraft will not remain in this orbit for much longer.

Today is the 211th anniversary of the discovery of Vesta, the first stop on Dawn's deep-space mission of exploration. For two centuries, that enigmatic world, the second largest in the main asteroid belt, appeared as little more than one of the myriad glowing jewels in the nighttime sky. In 2011-2012, Dawn transformed it into a complex, fascinating world, finding it to be more closely related to the terrestrial planets than to typical asteroids. Some of the discoveries are summarized here.

March 20, 2018 — Dawn Operating Smoothly as Team Prepares for Ambitious New Observations

Dawn has been in excellent health and continues to operate smoothly in orbit around Ceres. The operations team has made excellent progress in preparing to guide Dawn to lower altitudes and perform important new observations. Maneuvering with the ion propulsion system will begin next month. The latest Dawn Journal presents an overview of the plans for the two new orbits Dawn will occupy.

As the spacecraft continues its current elliptical orbit, it will descend today from 11,800 miles (19,000 kilometers) to 9,100 miles (14,600 kilometers) above the dwarf planet. On March 23, it will dip down to a little under 2,800 miles (4,400 kilometers) before going up again.

January 3, 2018 — Dawn Flight Team Planning for New Activities

The Dawn flight team is hard at work developing methods to fly Dawn much closer to Ceres than it has ever been. The December Dawn Journal describes some of the plans.

Meanwhile, the spacecraft is healthy as it continues in its high-altitude elliptical orbit. Over the course of the day today, the spacecraft will climb from 23,400 miles (37,600 kilometers) to 23,700 miles (38,200 kilometers). It will reach the crest of its orbit at 24,030 miles (38,670 kilometers) on Jan. 6.

November 17, 2017 - Dawn Marks Anniversary of Inhabiting the Main Asteroid Belt

All systems are working well as Dawn continues orbiting Ceres. The adventurer has now been a resident of the main asteroid belt beyond Mars for eight years.

In its elliptical orbit around Ceres, Dawn will descend today from 14,300 miles (23,100 kilometers) to 12,200 miles (19,600 kilometers). It takes the spacecraft a month to complete one orbital revolution. At 12:01 AM PST tomorrow, the ship will glide silently over the terminator, the boundary between night and day on the dwarf planet. (You can visualize that boundary in more familiar terms if you are accustomed to being on a planet. If you were at that location on the terminator on Ceres, or the equivalent point on Earth or any other planet, it would be sunrise, where night turns to day as the planet rotates.)

November 9, 2017 - Dawn Begins Another Slow Descent

Dawn is following its 30-day high-altitude elliptical orbit around Ceres as the flight team investigates flying down much lower in 2018, as described in the October Dawn Journal. The orbit changes slightly each month, so on Nov. 6, when Dawn reached the crest at 23,890 miles (38,450 kilometers), it was higher than it had been since June 14. Now the spacecraft is descending from that orbital peak. Today it will fall from 23,310 miles (37,510 kilometers) to 22,820 miles (36720 kilometers).

November 3, 2017 - Dawn Healthy as Team Investigates New Orbits Around Ceres

Dawn is operating smoothly as it continues orbiting Ceres once per month. During the day today, it will coast from 23,150 miles (37,250 kilometers) up to 23,540 miles (37,890 kilometers) above the exotic terrain. The spacecraft will reach its peak altitude this month on Nov. 6, when it will be 23,890 miles (38,450 kilometers) high. It will then begin its gradual fall down to below 3,100 miles (5,000 kilometers).

NASA determined that Dawn should conduct a second extended mission at Ceres. As the October Dawn Journal describes, this means the exploration of the dwarf planet will continue. The flight team is studying ways to take Dawn down to lower altitudes than ever before in 2018, which would allow the sophisticated probe to conduct valuable, exciting new observations.

September 27, 2017 - Dawn Celebrates 10 Years of Spaceflight

Dawn left its planet of origin 10 years ago this morning to undertake a daring interplanetary journey of discovery. Since then, it soared past Mars and explored what had been the two largest uncharted worlds in the inner solar system, Vesta and Ceres. Thanks to its uniquely capable ion propulsion system, it is the only spacecraft ever to orbit two extraterrestrial destinations. Today's Dawn Journal tracks the spaceship's progress through an extraordinary decade of travels in deep space.

Meanwhile, Dawn is healthy and operating smoothly in its elliptical orbit around Ceres. Over the course of the day today, it will ascend from 16,300 miles (26,200 kilometers) to 17,900 miles (28,700 kilometers) above the dwarf planet.

Dawn is too far from Earth to return even for a special event, but the team members at JPL mission control will celebrate the anniversary this afternoon with cake displaying the mission's interplanetary trajectory (shown in a less comestible form in the Dawn Journal).

September 7, 2017 - Sites on Ceres Receive New Names

The International Astronomical Union approved names for 25 more sites on Ceres discovered by Dawn. You can see a map of the dwarf planet with all the named features here. (We explained the system for naming Cerean features shortly before Dawn began its exploration of the alien world.)

Yesterday Dawn reached the peak of its elliptical orbit, cresting at an altitude of 23,790 miles (38,280 kilometers). Now the spacecraft is beginning a slow fall. Today it will descend from 23,760 miles (38,240 kilometers) to 23,600 miles (37,980 kilometers).

August 31, 2017 - Dawn's Long Residence at Ceres

Dawn entered orbit around dwarf planet Ceres in March 2015. The adventurer has now been at its solar system home for more than 2,400 Cerean days, or a little more than half a Cerean year.

Today's Dawn's elliptical orbit will take it from an altitude of 20,700 miles (33,400 kilometers) to 21,600 miles (34,800 kilometers).

August 23, 2017 - Dawn Dips Down and Flies Up Again

All of Dawn's systems are operating well, and the spacecraft is continuing to be operate smoothly in its elliptical orbit around dwarf planet Ceres.

On Aug. 22, Dawn dipped down to 3,230 miles (5,200 kilometers). The last time the probe was that close to the alien world of rock, ice and salt was Nov. 29, 2016. Now its orbital momentum is taking it to greater heights again. Over the course of the day today, the spacecraft will climb from 4,900 miles (7,900 kilometers) to 8,000 miles (12,900 kilometers).

August 16, 2017 - Dawn Passes Milestone in Distance

Dawn is monitoring cosmic rays as it follows an elliptical orbit around Ceres, completing one revolution every 30 days. Over the course of the day today, the spacecraft's altitude will decrease from 17,400 miles (28,000 kilometers) to 15,800 miles (25,400 kilometers). As Ceres tugs harder on Dawn, the orbiter's velocity will increase today from 89 mph (143 kph) to 101 mph (162 kph).

Dawn is held by Ceres' firm gravitational grip. As the spacecraft has been in orbit around Ceres since March 2015, Ceres has carried it along on the dwarf planet's orbit around the sun. Meanwhile, Earth follows its own independent heliocentric orbit. This week, Earth and its ambassador to Ceres are π hundred million miles apart. (That translates to the less numerically appealing 505.59 million kilometers.)

August 9, 2017 - Dawn Arcs over in Space and Passes Milestone in Time

Dawn crested an orbital hill on Aug. 7. As it reached an altitude of 23,740 miles (38,200 kilometers), the spacecraft gradually slowed to 46 mph (73 kph). Now its elliptical orbit is slowly taking it lower, and the craft will descend today from 23,450 miles (37,730 kilometers) to 23,080 miles (37,140 kilometers).

Dawn's deep space adventure passes a milestone of interest to terrestrial numerologists, as it marks π2 (pi squared) years of spaceflight this week.

August 2, 2017 - Dawn Operations Continuing

As Dawn measures cosmic rays, it is ascending in its elliptical orbit. Its average altitude today is 22,300 miles (35,800 kilometers). For comparison, that is the altitude of geosynchronous orbit at Earth. In geosynchronous orbit, satellites circle Earth once per day, the same rate at which Earth turns on its axis. Because Ceres' mass (and hence the strength of its gravitational pull) and the length of its day are different from Earth's, synchronous orbital altitude around the dwarf planet is different. With the Cerean day of a little more than nine hours, synchronous orbit is 450 miles (720 kilometers). Dawn descended through that altitude in November 2015 and ascended past it in September 2016.

July 28, 2017 - Dawn Sailing Upward

In its elliptical orbit around Ceres, Dawn dipped down to 3,280 miles (5,270 kilometers) on July 22. That is the closest it has come to its gravitational master since Nov. 29, 2016. The spacecraft spent more than eight months much lower than that, orbiting only 240 miles (385 kilometers) above the alien landscapes of rock, ice and salt. The flight team flew the probe higher to pursue ambitious new science objectives in three different sets of orbits (as described in October andNovember 2016 and May 2017).

Now Dawn's momentum is carrying it higher again. During the day today, the spacecraft will sail from 15,800 miles (25,500 kilometers) to 17,500 miles (28,100 kilometers).

July 19, 2017 - Dawn's Cosmic Ray Measurements Continue

As Dawn orbits Ceres, it is continuing to monitor cosmic rays in order to refine measurements of the atomic species down to about a yard (meter) beneath the surface of the dwarf planet. Today the spacecraft's altitude will decrease from 13,000 miles (20,900 kilometers) to 10,600 miles (17,100 kilometers). For comparison, GPS satellites orbit about 12,600 miles (20,200 kilometers) above Earth.

July 10, 2017 - Dawn at High Altitude

Dawn reached the peak of its elliptical orbit on July 7. After cresting at almost 23,700 miles (38,100 kilometers) above Ceres, the spacecraft began its slow fall back to lower altitudes. Today Dawn will descend from 23,240 miles (37,410 kilometers) to 22,820 miles (36,730 kilometers). It will reach its minimum altitude on July 22.

June 30, 2017 - Dawn Operating Smoothly

After adjusting its orbit, Dawn now revolves around Ceres once every 30 days. The spacecraft's altitude will increase from 19,200 miles (31,000 kilometers) to 20,400 miles (32,800 kilometers) over the course of the day today. In this high segment of its elliptical orbit, Dawn's average orbital velocity is 72 mph (116 kilometers per hour).

June 22, 2017 - Dawn Adjusting Orbit

Dawn is firing its ion engine to make a small adjustment to its elliptical orbit around Ceres. Today the orbit brings it down to the low point of 3,400 miles (5,400 kilometers). The spacecraft's momentum then will carry it back to the peak of its orbital altitude in July.

June 15, 2017 - Dawn Healthy after Solar Conjunction

Following conjunction, when Dawn and Ceres moved far enough from the sun that reliable communications could be established this week, the spacecraft transmitted details of its condition and its activities during the period it was out of contact with Earth. The flight team verified that Dawn is healthy and has continued to execute its assignments at Ceres. The probe's primary responsibility now is still measuring cosmic rays so scientists can refine their measurements of the atomic constituents of the dwarf planet down to about a yard (meter) underground.

Traveling in its elliptical orbit, Dawn will descend today from an altitude of 23,300 miles (37,500 kilometers) to 21,600 miles (34,700 kilometers).

June 6, 2017 - Dawn and Ceres Appear Close to the Sun

Mission controllers cannot communicate with Dawn now, as it is much too close to the Sun. The spacecraft is actually 3.7 times as far as the Sun, but from our terrestrial perspective, they are at practically the same place in the sky. Dawn is less than one solar diameter from the brilliant star. The May Dawn Journal describes this alignment, known as conjunction, and suggests how you can use the sun to direct your mind's eye at Earth's distant ambassador to the cosmos.

Despite the radio silence, engineers are confident that the spacecraft remains in its elliptical orbit. Succumbing to Ceres' gravitational pull, Dawn is slowly falling from its peak altitude. Today it will descend from 31,730 miles (51,070 kilometers) to 31,340 miles (50,430 kilometers).

May 31, 2017 - Dawn and Ceres Appear Close to the Sun

As Ceres (with its companion Dawn) and Earth move in their separate orbits around the sun, they are now on nearly opposite sides of our solar system's star, an alignment known as conjunction. From today until June 12, radio signals between Dawn and Earth may be distorted by passing close to the sun on their way back and forth. Therefore, communications are not reliable. The May Dawn Journal describes conjunction in more detail.

The spacecraft is continuing in its elliptical orbit around the dwarf planet. Today the ship reached its greatest altitude, 32,810 miles (52,800 kilometers). At this height, Dawn's orbital velocity is 49 mph (79 kilometers per hour). The February Dawn Journal explains how Dawn maneuvered to this orbit.

May 24, 2017 - Dawn's Mission Proceeding Well

Despite losing a reaction wheel last month, Dawn is performing flawlessly in orbit around Ceres. The May Dawn Journal summarizes the probe's use of reaction wheels and how the flight team has recovered from the three loses over the past seven years.

Dawn's altitude today will increase from 31,290 miles (50,360 kilometers) to 31,690 miles (51,010 kilometers). (Near the peak of its elliptical orbit, the daily change in altitude is less than it has been recently. Therefore, as during part of April, we are rounding off the altitudes to the nearest 10 rather than the nearest 100.)

The mission control team is preparing for Dawn to be nearly aligned with the sun, which will make radio communications unreliable. The May Dawn Journal also provides a way for you to find the distant ship using the sun as a celestial landmark.

May 18, 2017 - Dawn Gets a Navigational Fix

On May 16, Dawn photographed Ceres to help navigators improve their measurements of its elliptical orbit. The spacecraft is in such a high orbit that it takes almost two months for one revolution. Dawn's altitude will increase today from 27,500 miles (44,300 kilometers) to 28,300 miles (45,500 kilometers).

May 11, 2017 - Dawn is Healthy in Orbit High Above Ceres

Dawn is healthy and continuing to follow the elliptical orbit that it flew to in order to observe Ceres' opposition surge on April 29. Over the course of the day today, the spacecraft will ascend from an altitude of 19,700 miles (31,700 kilometers) to 21,100 miles (33,900 kilometers). This high above the dwarf planet, Dawn's orbital velocity is 100 mph (160 kilometers per hour).

The explorer's primary responsibility is monitoring the noise from cosmic rays so scientists can remove that unwanted component from the measurements of nuclear radiation it made at low altitude in 2015-2016.

May 5, 2017 - Dawn Continuing to Operate Smoothly in Elliptical Orbit

On May 1, Dawn sent to Earth the last of its data from opposition, when it observed a fully illuminated Ceres as it flew across the line from the sun to the dwarf planet. The team has confirmed that the spacecraft acquired all the planned pictures and spectra, as described in theApril Dawn Journal

Dawn is continuing to measure cosmic rays in order to improve its low-altitude measurements of Ceres' nuclear radiation, providing further insights into the atomic constituents down to about a yard (meter) underground.

The spaceship maneuvered extensively with its ion engine over a period of two months to reach its current orbit so it could see Ceres at opposition on April 29. (The complex flight plan is described in the February Dawn Journal.) Today this elliptical orbit carries Dawn from an altitude of 10,400 miles (16,800 kilometers) to 11,900 miles (19,200 kilometers).

May 1, 2017 - Dawn Observes Ceres at Opposition

Dawn performed the planned observations of Ceres at opposition. As explained in the April Dawn Journal, the spacecraft took pictures as well as infrared and visible spectra when it was close to the line from the sun to the bright center of Occator Crater on April 29. Later on April 29 and April 30, Dawn transmitted some of its data to NASA's Deep Space Network, and it will finish today.

As Dawn approaches the lowest point in its orbit, its altitude today will decrease from 9,700 miles (15,500 kilometers) to 8,800 miles (14,100 kilometers). On May 2, the spacecraft will come within 8,600 miles (13,830 kilometers) of the dwarf planet before its elliptical orbit takes it to higher altitudes again. The orbit is described in the February Dawn Journal, and illustrated in this diagram.

The ship is healthy and operating well, using hydrazine to control its orientation following the April 23 failure of a third reaction wheel.

April 25, 2017 - Dawn Observing Ceres; 3rd Reaction Wheel Malfunctions

NASA's Dawn spacecraft is preparing to observe Ceres on April 29 from an "opposition" position, directly between the dwarf planet’s mysterious Occator Crater and the sun. This unique geometry may yield new insights about the bright material in the center of the crater. The April Dawn Journal describes the plan.

While preparing for this observation, one of Dawn's two remaining reaction wheels stopped functioning on April 23. By electrically changing the speed at which these gyroscope-like devices spin, Dawn controls its orientation in the zero-gravity, frictionless conditions of space.

The team discovered the situation during a scheduled communications session on April 24, diagnosed the problem, and returned the spacecraft to its standard flight configuration, still with hydrazine control, on April 25. The failure occurred after Dawn completed its five-hour segment of ion thrusting on April 22 to adjust its orbit, but before the shorter maneuver scheduled for April 23-24. The orbit will still allow Dawn to perform its opposition measurements. The reaction wheel's malfunctioning will not significantly impact the rest of the extended mission at Ceres.

Dawn completed its prime mission in June 2016, and is now in an extended mission. It has been studying Ceres for more than two years, and before that, the spacecraft orbited protoplanet Vesta, sending back valuable data and images. Dawn launched in 2007.

The Dawn operations team has been well prepared to deal with the loss of the reaction wheel. The spacecraft is outfitted with four reaction wheels. It experienced failures of one of the wheels in 2010, a year before it entered orbit around Vesta, and another in 2012, as it was completing its exploration of that fascinating world. (See issues with these devices). When a third reaction wheel stopped working this week, the spacecraft correctly responded by entering one of its safe modes and assigning control of its orientation to its hydrazine thrusters.

Today, Dawn's elliptical orbit will bring it from an altitude of 17,300 miles (27,900 kilometers) to above Ceres to 15,800 miles (25,400 kilometers).

April 21, 2017 - Dawn to Adjust Orbit

To complete its delicate orbital maneuvering, Dawn will adjust its trajectory. Based on the latest navigational data, the flight team has developed a plan to thrust with the ion engine for about five hours on April 22 and a little more than four hours on April 23-24. These trajectory correction maneuvers will bring the spacecraft's orbit closer to the line from the sun to Occator Crater on April 29, as described in the February Dawn Journal. When Dawn crosses that line, it will photograph the bright central region of the crater, and scientists will use the pictures to investigate detailed properties of the material on the ground. (See the March Dawn Journal for an explanation of the science behind this.)

Following its elliptical orbit, Dawn will descend today from 24,000 miles (38,600 kilometers) above the dwarf planet to 22,800 miles (36,700 kilometers).

April 17, 2017 - Navigators Verifying Dawn's New Orbit

The Dawn navigation team is studying the spacecraft's new orbit to determine whether a trajectory correction maneuver is needed. As always, they will use the probe's radio signal, from which they can determine Dawn's distance and its velocity toward or away from Earth (but not across the line of sight), as well as the ship's detailed records of its recent ion thrusting and every time it fired a hydrazine jet to control its orientation. (The hydrazine is never used to modify the orbit, because it is far less efficient than the ion engine, but it does alter the orbit a little.) Navigators also will use Dawn's photos of Ceres, taken on April 15 and very early today, which will help pin down its location in orbit.

Because of where Ceres and Earth are in their independent orbits around the sun, it takes a radio signal one hour today to make the round trip from Earth to Dawn and back. (The navigational analysis depends on the exact time, measured to an accuracy of better than 10 billionths of a second.) The time is increasing about five seconds per day.

Dawn's altitude today will decrease from 27,910 miles (44,920 kilometers) to 27,040 miles (43,520 kilometers). The target for this orbit is to be at an altitude of about 12,400 miles (20,000 kilometers) when Dawn flies between the sun and Occator Crater on April 29. The most recent Dawn Journal describes how photographs from that special position may reveal properties of the reflective material at the center of the crater.

April 13, 2017 - Dawn Completes Third Ion Thrust Segment

Last night Dawn completed the third and longest period of ion thrusting to change its orbit. The sophisticated probe will take pictures on April 15 and 17 to help navigators determine its current orbit more accurately. In case the orbit needs any adjustment, the flight team has scheduled a window for further ion thrusting on April 22-24. (See the February Dawn Journal for an explanation of Dawn's orbital maneuvering and the navigation pictures.)

Dawn is slowly descending in its elliptical orbit. Over the course of today, its altitude will decrease from 30,740 miles (49,470 kilometers) to 30,130 miles (48,500 kilometers).

The reason for changing Dawn's orbit around Ceres is to position the spacecraft between the sun and the bright material at the center of Occator Crater later this month. This will allow the spacecraft to make measurements that scientists can use to discover more about the nature of those reflective materials. (The March Dawn Journal explains how high altitude pictures can reveal microscopic properties of the ground.)

April 10, 2017 - Dawn on Course and on Schedule

Dawn is continuing to use its ion engine to rotate its orbital plane around Ceres. This maneuvering is designed to allow the spacecraft to fly directly between the highly reflective center of Occator Crater and the sun. Pictures from that position may help scientists learn more about the properties of the material on the ground there. (See the March Dawn Journal for an explanation of the science behind this "opposition surge.")

As Dawn maneuvers, it is descending. During the day today, its altitude will decrease from 32,200 miles (51,820 kilometers) to 31,780 miles (51,150 kilometers). This third (of four) ion-thrust periods is scheduled to end on April 12. (The February Dawn Journal describes Dawn's complicated route to its next orbit.)

April 7, 2017 - Dawn Turning Its Orbital Plane

High above Ceres, Dawn is making good progress thrusting with its ion engine to swivel the plane of its orbit around the dwarf planet. Having reached the peak of its elliptical orbit this week, the spacecraft is starting to fall to lower altitude as Ceres exerts its relentless gravitational pull. Over the course of the day today, Dawn will descend from 32,930 miles (52,990 kilometers) to 32,780 miles (52,750 kilometers). The objective of the complex maneuvers (which are explained in detail in the February Dawn Journal) is to modify the ship's orbit so that it will pass through the line from the sun to the bright center of Occator Crater on April 29 at an altitude of 12,400 miles (20,000 kilometers). The March Dawn Journal explains how photographs from that special position may provide insight into the nature of the reflective material covering the ground.

April 4, 2017 - Dawn Begins Ion Thrusting Again

Earlier today, Dawn began 8.5 days of ion thrusting. This is the third and largest of the four maneuvers the spacecraft is executing to change its orbit around Ceres, as explained in theFebruary Dawn Journal. During this thrust period, Dawn will swivel its orbit by almost 90 degrees. These complicated orbital operations are designed to allow the probe to fly directly between the sun and Occator Crater's famous bright region. Photographs taken from that vantage point may allow scientists to discover properties of the material on the ground, even at the microscopic level. (See the March Dawn Journal for the science behind this remarkable capability.)

Rotating the plane of Dawn's orbit is most efficient when the spacecraft is at high altitude and traveling slowly. That's why the two previous maneuvers propelled the ship to high altitude. (The three diagrams in February may help clarify this.) Over the course of the day today, Dawn ascends from 32,810 miles (52,810 kilometers) to 32,950 miles (53,020 kilometers). As it soars higher and higher, the spacecraft is slowing down under Ceres' relentless gravitational pull. Just as a ball thrown high goes slowest at the peak of its arc, Dawn's average orbital velocity today is only 44 mph (71 kilometers per hour). At this low speed, the daily change in altitude is less than it has been recently. Therefore, we are rounding off the altitudes today to the nearest 10 rather than the nearest 100. On the night of April 5, Dawn will reach the crest of its orbit, 32,990 miles (53,090 kilometers) above the dwarf planet.

March 30, 2017 - Dawn Team Preparing for More Ion Thrusting

Dawn's orbit today carries the spacecraft from an altitude of 31,000 miles (49,900 kilometers) to 31,500 miles (50,700 kilometers). On March 28, the spacecraft took pictures of Ceres to help navigators plot its course in this highly elliptical orbit as accurately as possible. Their results are being incorporated into final preparations for the resumption of ion thrusting on April 4 to swivel Dawn's orbit. As described in the February Dawn Journal, this will be the third of four segments of maneuvering to allow the explorer to take special photos of Ceres at the end of April. Scientists will use the pictures to measure how bright the center of Occator Crater is when viewed along the same direction as the incoming sunlight. The March Dawn Journal explains how this can provide insight into fine details of the material on the ground.

March 27, 2017 - Dawn's Mission Continuing Smoothly

Dawn is healthy and performing all of its duties flawlessly, including measuring cosmic rays high above Ceres. Although slowing as it ascends in orbit because of Ceres’ gravitational pull, today the spacecraft will go from an altitude of 29,100 miles (46,900 kilometers) to 29,800 miles (48,000 kilometers). (For an explanation of Dawn's current orbit, and the changes it will make soon, see the February Dawn Journal.)

March 22, 2017 - Dawn Sailing Upward

With the momentum it gained from ion thrusting earlier this month, Dawn is continuing to ascend in its orbit around Ceres. Today it will climb from 24,300 miles (39,100 kilometers) to 25,500 miles (41,000 kilometers) above the dwarf planet. As it reaches its peak altitude early next month, Dawn will use its ion engine to change the angle of its orbit. (For details of this complex cosmic choreography, see the February Dawn Journal.)

March 17, 2017 - Dawn Coasting to Higher Altitudes

Dawn is continuing to measure cosmic rays, which is its highest priority assignment. Following the orbital path it maneuvered to earlier this week, the spaceship is now coasting to higher and higher altitudes. Today Dawn will glide from 17,000 miles (27,300 kilometers) to 18,700 miles (30,000 kilometers). As described in the most recent Dawn Journal, this temporary orbit will position the spacecraft so it can use its ion engine early next month to swivel its orbit around Ceres.

For those of you who missed Pi Day on March 14, don't despair. You can celebrate it tomorrow when Dawn is pi hundred million miles from Earth.

March 13, 2017 - Dawn Completes Second Thrust Segment

Last night, orbiting more than 8,900 miles (more than 13,400 kilometers) above Ceres, Dawn completed the second of four periods of ion thrusting. As explained and illustrated in the February Dawn Journal, after powering its way in orbit, the spacecraft now has so much momentum that it will coast upward for nearly a month. Over the course of the day today, the ship will sail from 9,100 miles (14,600 kilometers) to 11,100 miles (17,900 kilometers).

The Dawn Journal also explains that this maneuvering is designed to change Dawn's orbit so it can perform unique measurements of the highly reflective salt deposits in Occator Crater.

March 10, 2017 - Dawn Thrusting to New Orbit

On March 8, Dawn began five days of ion thrusting. This is the second of four thrust periods the spacecraft is executing over two months. The maneuvering will change its orbit around dwarf planet Ceres to let the spacecraft fly through the imaginary line from Occator Crater to the sun at the end of April. Today Dawn reaches down to about 6,300 miles (10,200 kilometers), the lowest altitude of its current orbit, even as it is using its ion engine to fly higher. (For details, including diagrams of the orbit changes, see the February Dawn Journal.)

March 7, 2017 - Dawn Passes Second Anniversary at Ceres

Yesterday Dawn marked the second anniversary of arriving at Ceres, a major milestone in its ambitious and spectacular exploration of a fascinating alien world. The event also marked Dawn becoming the first spacecraft to reach a dwarf planet, the first spacecraft to orbit one, and the first spacecraft to orbit any two extraterrestrial destinations.

Dawn is continuing to measure cosmic rays to improve the accuracy of its measurements of Ceres' atomic composition. Today the ship's orbit takes it from 9,200 miles (14,800 kilometers) above Ceres to 8,400 miles (13,500 kilometers). Tomorrow night Dawn will be at the correct orbital location to begin the second segment of its ion thrusting maneuvers to change its orbit so it can make special measurements of the bright material in Occator Crater at the end of April. (The February Dawn Journal has the full story.)

March 2, 2017 - Dawn Orbiting High Above Ceres

Dawn is healthy and all systems are operating well. As explained in the February Dawn Journal,the explorer has completed the first of four segments of ion thrusting to maneuver to a new orbit where it will make special measurements to gain insight into the nature of the reflective material in Occator Crater. In its current orbit, Dawn will ascend today from an altitude of 9,400 miles (15,100 kilometers) to 9,900 miles (15,900 kilometers).

You can do your own celestial navigation today. The February Dawn Journal explains how to use the moon to locate Dawn and Ceres in the sky before the moon sets this evening.

February 27, 2017 - Dawn on Course for New Orbit

Yesterday Dawn completed the first of four segments of ion thrusting to maneuver to a new orbit around Ceres. The spacecraft raised its orbital altitude with four days of firing its ion. Next week it will begin a five-day thrust period. Over the course of the day today, Dawn's present orbit will carry it from 6,700 miles (10,700 kilometers) to 7,700 miles (12,300 kilometers) above the dwarf planet.

The February Dawn Journal explains the complex and elegant maneuvers Dawn will execute over the next two months to fly to a new orbit so it can perform a unique observation of the bright region in Occator Crater at the end of April.

February 23, 2017 - Dawn Maneuvering to New Orbit Around Ceres

After arriving in its sixth science orbit around Ceres in December, Dawn completed all of its assigned work there. Now the spacecraft is using its ion engine to fly to a new orbit in order to make special measurements in April. (The January Dawn Journal explained the nature of the new observations.) For the first stage of its maneuvering, Dawn began four days of ion thrusting on Feb. 22.

February 15, 2017 - Dawn Captures More Views of Ceres

Dawn trained its camera and mapping spectrometer on Ceres again on Feb. 10-11. The spacecraft has transmitted some of its findings to Earth and will radio the rest tomorrow. The explorer is also continuing to measure cosmic rays to improve the accuracy of its measurements of Ceres' nuclear radiation.

February 8, 2017 - Dawn Healthy and Productive

Dawn is operating very smoothly in its sixth orbital phase at Ceres. It finished radioing its latest pictures to Earth on Feb. 6 and will acquire more pictures and visible spectra on Feb. 10-11. Meanwhile, as the probe continues to revolve around Ceres every eight days, it is monitoring cosmic rays to help remove "noise" from its low altitude measurements of nuclear radiation.

The latest Dawn Journal describes an intriguing new assignment for the spacecraft in its ongoing exploration of the dwarf planet.

February 1, 2017 - Dawn Transmitting Latest Pictures to Earth

Dawn smoothly executed its Ceres observations on Jan. 27, including the first photography in three months. The spacecraft transmitted its new spectra and some of the pictures to Earth on Jan. 30. Today it is beaming more of the pictures home. It will send the last of the data next week. Dawn is also continuing to perform its primary assignment of measuring cosmic rays to improve the census of the atomic species it made when it was at a lower altitude.

The explorer has more in store during the remaining five months of its extended mission. To learn about the recent observations plus plans for new orbital maneuvers and new photography, see the January Dawn Journal.

January 27, 2017 - Dawn Observing Ceres from a New Perspective

Dawn is taking pictures and spectra of Ceres today for the first time since arriving in its current orbit early last month. As illustrated here, the spacecraft is seeing Ceres at a new angle. The data will be transmitted to Earth next week.

In addition to these bonus observations, Dawn is continuing its primary activity of measuring cosmic rays to enhance the determination of the atomic constituents of the material down to about a yard (meter) underground.

January 23, 2017 - Dawn Healthy and Operating Normally

In a communications session with the Deep Space Network on Jan. 17, mission controllers observed that Dawn was in safe mode, as explained in the Jan. 19 mission status update.Shortly after that update was posted, the team guided Dawn out of safe mode. Since then, all telemetry confirm that it is healthy. The team radioed additional instructions on Jan. 20 and 21 to return the robotic probe to its standard configuration. Later this week, it will resume measuring cosmic rays to improve the quality of earlier measurements of nuclear radiation from the dwarf planet. Meanwhile, the investigation into the software glitch that triggered safe mode is continuing.

Orbiting Ceres once every eight days, Dawn's average altitude today is 5,740 miles (9,230 kilometers). Yesterday the spacecraft reached its highest point on this orbital loop of 5,800 miles (9,340 kilometers), and now its elliptical path is bringing it closer to the dwarf planet. It will descend to its lowest altitude on Jan. 26, when it will be 4,680 miles (7,530 kilometers) high.

January 19, 2017 - Dawn Team Investigates Software Glitch

Dawn has been orbiting Ceres and measuring cosmic rays to improve the quality of earlier measurements of nuclear radiation from the dwarf planet. Throughout its nine-year interplanetary mission, the spacecraft's main computer has constantly performed calculations about its location in the solar system. On Jan. 14, software detected a discrepancy in those calculations and called for safe mode, a standard configuration used to ensure the spacecraft is safe and stable when it encounters conditions its programming cannot accommodate. During the next communications session with the Deep Space Network on Jan. 17, mission controllers observed that Dawn was in safe mode.

Engineers have since confirmed that all spacecraft systems are healthy, and they are investigating the details of what triggered the anomalous condition in the calculations. The flight team will continue their analyses and determine next week when to resume normal spacecraft operations. Dawn's primary objective now remains the cosmic ray measurements, and there is more than enough time in the extended mission to acquire the desired data.

Now in its sixth science orbit since arriving at Ceres in March 2015, the veteran explorer takes almost eight days to complete each elliptical revolution. During that time, Dawn's altitude ranges from 4,670 miles (7,520 kilometers) to 5,810 miles (9,350 kilometers). Today the ship's average height above the alien world is 4,730 miles (7,620 kilometers).

January 12, 2017 - Dawn Operating Smoothly in Elliptical Orbit

Dawn is making excellent progress in its measurement of cosmic rays to enhance the measurements it made closer to Ceres to determine the dwarf planet's atomic constituents.

The spacecraft takes almost eight days to complete each elliptical orbital revolution, going as low as 4,670 miles (7,520 kilometers) and as high as 5,810 miles (9,350 kilometers). Over the course of the day today, the ship will sail from 4,770 miles (7,670 kilometers) up to 5,180 miles (8,330 kilometers).

January 5, 2017 - Dawn Healthy and Productive as 2017 Begins

Dawn has gotten the new year off to a smooth start. The spacecraft is healthy and operating well in orbit around dwarf planet Ceres. Now halfway through its one-year extended mission, the probe is continuing to measure cosmic rays to improve atomic composition measurements it made at low altitude.

Jan. 1 was the 216th anniversary of Giuseppe Piazzi's discovery of Ceres. See the December Dawn Journal for some of Dawn's latest discoveries about this former planet.

December 30 - Dawn Concluding Another Successful Year

Dawn is wrapping up the year in its sixth science orbit since arriving at Ceres in March 2015. Following an elliptical orbit around the dwarf planet, the spacecraft's average altitude today is 5,780 miles (9,310 kilometers).

The December Dawn Journal describes this new orbit more and presents some of Dawn's latest discoveries about the alien world it is exploring.

December 21 - Dawn Measuring Cosmic Rays

In its sixth science orbit around Ceres, Dawn is continuing to measure cosmic rays to improve its low altitude measurements. It takes almost eight days to complete one elliptical orbit. Today, the spacecraft's average altitude is about 5,470 miles (8,810 kilometers).

December 16 - Dawn Team Announces Discoveries about Ice on Ceres

Yesterday the Dawn team presented news about widespread ice just below Ceres' surface, as well as other discoveries about ice on the dwarf planet. You can read about it in this JPL news release.

The discovery of subsurface ice comes from Dawn's measurements of nuclear radiation during the eight months the spacecraft orbited Ceres at 240 miles (385 kilometers). Now the probe is in a high-altitude elliptical orbit, ranging between 4,670 miles (7,520 kilometers) and 5,810 miles (9,350 kilometers) in order to squeeze even more information from those earlier measurements. (See the November Dawn Journal for details.)

December 8 - Dawn Collecting Science Data in New Ceres Science Orbit

Dawn is healthy and making cosmic ray measurements in its new science orbit. (The November Dawn Journal explains the objective of these measurements.)

This sixth Ceres science orbit is elliptical, and navigators' initial measurements show that it ranges in altitude between 4,670 miles (7,520 kilometers) and 5,810 miles (9,350 kilometers).

December 5 - Dawn Reaches Sixth Ceres Science Orbit

This morning Dawn completed a month of ion thrusting to change its orbit around Ceres. It is scheduled to initiate a telecommunications session this afternoon to report on its status. Navigators then will begin making accurate measurements of its orbit, but the spacecraft should be in an elliptical orbit that stays more than 4,500 miles (7,200 kilometers) above Ceres. From this altitude, it will be able to measure the cosmic ray noise in order to improve the data on Ceres' nuclear radiation it accumulated during eight months at an altitude of 240 miles (385 kilometers). (This is explained in the November Dawn Journal).

December 2 - Dawn Closing in on New Orbit

Dawn's ion engine is taking the spacecraft higher and higher above dwarf planet Ceres. Today the spacecraft's average altitude is 4,140 miles (6,660 kilometers). It now takes Dawn more than 5.5 days to complete one orbital revolution.

Ion thrusting is scheduled to conclude on Dec. 5, by which time the probe will be high enough to measure cosmic rays in order to enhance its low altitude measurements of nuclear radiation emitted by Ceres. (This paradox of flying higher to improve data collected at low altitude is explained in the November Dawn Journal).

November 28 - Dawn Making Good Progress to New Orbit

As Dawn continues to raise its orbit, its average altitude today is 3,130 miles (5,040 kilometers).

The November Dawn Journal describes how flying to a higher orbit will help scientists learn more about Ceres. It also explains that with all the ion thrusting Dawn has accomplished since it left Earth in 2007, the spacecraft has now changed its own speed by a remarkable 25,000 mph (40,000 kilometers per hour).

November 23 - Dawn's Ascent Continues Smoothly

Gradually maneuvering to a higher orbit with its ion engine, Dawn's average altitude today is 2,360 miles (3,790 kilometers). Even as mission controllers take time for Thanksgiving, they will check in with Dawn occasionally through NASA's Deep Space Network to verify that the distant spacecraft is operating smoothly.

November 21 - Dawn Climbing Higher

As Dawn spirals higher, its average altitude today is 2,110 miles (3,400 kilometers). It now takes more than two days for the spacecraft to complete one orbital revolution around Ceres.

The spacecraft will continue ion thrusting for two more weeks.

November 18 - Dawn Receives Update from Earth

Dawn stopped ion thrusting on schedule yesterday afternoon and turned to point its main antenna to Earth. Mission controllers at JPL transmitted an updated flight plan to the distant spacecraft. Dawn resumed ion thrusting today shortly after 3:00 a.m. PST to continue its upward spiral.

Dawn's average altitude today is 1,750 miles (2,820 kilometers).

November 15 - Dawn Ascending Above Ceres

Dawn is making good progress maneuvering to its next science orbit. The spacecraft's average altitude today is about 1,560 miles (2,510 kilometers). Over the course of the day, Dawn's ion thrusting will raise the altitude by almost 75 miles (120 kilometers).

November 11 - Dawn On Course and On Schedule

Dawn's graceful spiral ascent to its sixth science orbit around Ceres is going very well. The spacecraft's average altitude today is about 1,270 miles (2,040 kilometers). It now takes the ship more than 27 hours to complete each orbital revolution. (During the eight months Dawn operated at 240 miles, or 385 kilometers, in altitude, it circled Ceres every 5.4 hours.)

Ion thrusting is scheduled to conclude in early December when Dawn is more than 4,500 miles (7,200 kilometers) above the dwarf planet.

November 8 - Dawn Climbing to Higher Altitude Orbit

Dawn began ion thrusting on schedule on Nov. 4. The spacecraft is now spiraling upward to its sixth science orbit around Ceres. Today Dawn's average altitude is 1,100 miles (1,770 kilometers), or nearly 200 miles (300 kilometers) above its fifth science orbit.

Ceres and its permanent companion are now 2.867 AU (266.5 million miles, or 428.9 million kilometers) from the sun, closer than any time since Dawn entered orbit around the dwarf planet in March 2015.

November 4 - Dawn Ready to Begin a New Maneuver Spiral

Dawn completed all of its planned activities at an orbital altitude of 920 miles (1,480 kilometers). This week, after the spacecraft transmitted the last of its Ceres science data to Earth, engineers swapped from the primary hydrazine-fueled reaction control system thrusters to the backup thrusters to avoid overusing them. The team also performed a routine verification of the health of the backup camera. (See the October Dawn Journal for more on these activities.)

Dawn is now ready to undertake more than a month of maneuvering to a new orbit. Ion thrusting with engine #2 is scheduled to begin shortly before 5:00 p.m. PDT today.

October 31 - Dawn Completes Another Observation Campaign

Dawn successfully concluded its fifth program of observations in Ceres orbit by transmitting the last of its scientific measurements to Earth on Oct. 29. This month's Dawn Journal describes some of the spacecraft's work in this phase of its exploration of the dwarf planet.

The flight team is now preparing to undertake a new set of maneuvers with the ion propulsion system. Dawn's next spiral to a higher altitude orbit is scheduled to begin on Nov. 4.

October 27 - Dawn's Investigations Going Smoothly

Dawn is healthy and conducting all the commanded measurements of Ceres with its camera and spectrometers. With an orbit period of 18.9 hours, the spacecraft has flown over the illuminated hemisphere 14 times since observations began on Oct. 16, acquiring the planned data each time.

October 20 - Dawn Conducting New Measurements of Ceres

Dawn began its new observations of Ceres on schedule on Oct. 16 at an altitude of 920 miles (1,480 kilometers). Circling the dwarf planet every 18.9 hours, the spacecraft acquires spectra and photographs as it flies over the sunlit surface. Sometimes it rotates to point its main antenna to Earth as it flies over the side in darkness and transmits its measurements to NASA's Deep Space Network. (On other orbits, the spacecraft waits, preserving hydrazine rather than executing additional turns.)

As Earth and Dawn (in orbit around Ceres) follow their separate orbits around the sun, this weekend they will be closer than usual. On Oct. 22, they will be 1.90 AU (177 million miles, or 284 million kilometers) apart, the smallest distance from June 2014 to December 2017.

October 12 - Dawn Team Preparing for New Ceres Observations

Orbiting Ceres at an altitude of about 920 miles (1,480 kilometers), Dawn is traveling over the alien landscapes at about 400 mph (645 kilometers per hour). After ion thrusting concluded last week, navigators measured the parameters of the orbit very accurately. The actual orbit is so close to the planned orbit that the expected refinements in the timing of observations are unnecessary. To optimize the quality of the data to be collected, engineers are making small adjustments to the direction the spacecraft will point its sensors for some of the measurements. Science observations will begin on Oct. 16.

October 6 - Dawn Completes Ascent Spiral

Dawn concluded its ascent on schedule last night by stopping its ion engine at 11:02:48 p.m. PDT. When it began the spiral climb on Sept. 2, the spacecraft was in a 5.4-hour orbit at an altitude of 240 miles (385 kilometers). Now it is in an 18.9-hour orbit about 920 miles (1,480 kilometers) above Ceres. Navigators will measure its orbital parameters carefully to pin down the details. Mission controllers will use the results to refine the timing of Dawn's new observations of the dwarf planet, which are scheduled to begin on Oct. 16.

Nine years ago today, Dawn thrust with its remarkable ion propulsion in space for the first time. As explained in the latest Dawn Journal, the explorer has used its ion engines extensively in the intervening nine years to accomplish extraordinary feats in its interplanetary expedition.

October 3 - Dawn Thrusting to Higher Altitude

Dawn is healthy and continuing to use its ion engine to spiral higher above Ceres. Today the spacecraft's average altitude is 830 miles (1,335 kilometers). Dawn's orbit period is more than 16 hours.

September 30 - Dawn Begins Final Segment of Ascent

During the weekly telecommunications session last night, mission controllers transmitted to Dawn the instructions for the final segment of ion thrusting in its ascent spiral. Shortly before 6:00 a.m. PDT today, the spacecraft resumed powered flight. It is scheduled to stop thrusting at 11:03 p.m. on Oct. 5.

Dawn's average altitude today is 730 miles (1,175 kilometers), three times higher than the mapping orbit it was in from December 2015 until the beginning of this month.

September 27 - Dawn Performing Well on its Ninth Anniversary

Dawn is operating perfectly and making excellent progress as it climbs above Ceres. Its average height today is 660 miles (1060 kilometers). At this altitude, it takes Dawn 13 hours to complete one revolution around the dwarf planet.

Today is Dawn's ninth anniversary of being in space. This month's Dawn Journal reviews the explorer's progress since embarking on its ambitious interplanetary adventure.

September 23 - Dawn's Spiral Ascent Proceeding Well

Dawn is continuing its orbital ascent. Today its average altitude is about 560 miles (900 kilometers). As the spacecraft climbs higher, its orbital velocity naturally decreases. Ceres' gravitational pull is weaker, so Dawn can move more slowly to counter it. In its lowest altitude orbit at 240 miles (385 kilometers), Dawn circled at about 610 mph (980 kilometers per hour). At its current altitude, orbital velocity is 480 mph (775 kilometers per hour).

Dawn has now completed more than 1,500 revolutions around Ceres since its arrival on March 6, 2015. By coincidence, during the same time, Ceres has turned on its axis about 1,500 times.

September 19 - Dawn on Course as it Spirals Up

Dawn is on course and on schedule as it uses ion engine #2 to spiral upward. The spacecraft's average altitude today is about 485 miles (780 kilometers). In a higher orbit, Dawn travels more slowly and each revolution takes longer. Yesterday the ship passed above the altitude at which it takes as long to circle Ceres as Ceres takes to rotate on its axis. One Cerean day is nine hours and four minutes. Now even higher, Dawn's orbit period has increased to more than nine-and-a-half hours.

September 15 - Dawn to Receive Updated Flight Plan Today

Dawn is steadily raising its orbit, and all systems are functioning well. Shortly after 4:30 p.m. PDT today, the spacecraft will pause ion thrusting and rotate to point its main antenna to Earth for a telecommunications session with NASA's Deep Space Network. Mission controllers at JPL will transmit an updated flight plan to guide Dawn through the next week of maneuvering. Thrusting will resume about 4:00 a.m. tomorrow. This pattern is followed each week as the distant probe flies to its next science orbit. (We explained the reason for these regular updates here.)

Dawn's average altitude today is about 415 miles (670 kilometers).

September 12 - Dawn Spiraling Higher

Dawn is continuing to thrust with ion engine #2, spiraling to higher orbits above Ceres. Dawn's average altitude is more than 365 miles (590 kilometers) today. At this height, it takes the spacecraft 7.5 hours to complete one orbital revolution.

September 9 - Dawn's Ascent Continues Smoothly

As planned, Dawn paused its ion thrusting yesterday in order to aim its main antenna at Earth. It reported back on its health and the progress of maneuvering to raise its orbit. Mission controllers transmitted the instructions for the next week of ion thrusting, and then the spacecraft resumed its ascent spiral.

Dawn's average orbital altitude today is almost 325 miles (520 kilometers).

September 6 - Dawn Climbing to Higher Altitude

On schedule on Sept. 2, Dawn began firing its ion engine to raise its orbital altitude. Its average height above the alien world today is 290 miles (465 kilometers). As the spacecraft moves higher, it orbits more slowly because Ceres' gravitational hold weakens. In Dawn's low orbit at 240 miles (385 kilometers), each revolution took less than 5.5 hours. Today, Dawn takes more than six hours to circle the dwarf planet.

September 2 - Dawn Begins Maneuvering to Higher Altitude

Dawn radioed the last of its low altitude data to JPL this morning, marking the conclusion of an outstandingly productive phase of its exploration at Ceres from 240 miles (385 kilometers) above the alien world. Then the spacecraft turned its main antenna away from Earth on schedule to begin five weeks of maneuvering to a higher orbit. (For details, see the August Dawn Journal.)

Dawn's ultraefficient ion engine will consume very little xenon propellant during the upward spiral. The thrust is very gentle so progress will be gradual. By the end of the day today, the probe will have moved to an orbit about 6 miles (10 kilometers) higher.

Fascinating new findings from Dawn's scientific investigations of Ceres are highlighted in a Sept. 1 news release.

August 31 - Dawn Completing Low Altitude Phase of Ceres Mission

After more than eight months scrutinizing Ceres from an altitude of 240 miles (385 kilometers), Dawn is preparing to move to a new orbit. The spacecraft has collected an extraordinary wealth of information on the dwarf planet and will transmit its final findings to NASA's Deep Space Network from today through Sept. 2.

Dawn is scheduled to begin ion thrusting on Sept. 2 shortly before 9:00 a.m. It will spend most of the subsequent five weeks spiraling to a higher altitude.

This month's Dawn Journal describes some of the measurements Dawn has made at this altitude and looks ahead to raising the orbit.

August 24 - Dawn Very Productive in Extended Mission

As Dawn continues its extended mission, it is using all of its scientific instruments to study Ceres. The probe is scheduled to radio its most recent pictures and other data to Earth from about 11:00 p.m. PDT on Aug. 26 until shortly after 5:00 a.m. PDT on Aug. 28. It will then turn its sights back to Ceres.

The spacecraft has been carrying out all of its activities perfectly. Scientists have received an extraordinary wealth of information about the dwarf planet, far exceeding what they anticipated when Dawn descended to this fourth science orbit more than eight months ago.

August 17 - Dawn Healthy and Performing Well

Dawn is collecting new Ceres data as it orbits the dwarf planet every 5.4 hours at an altitude of 240 miles (385 kilometers).

On Aug. 13-14, the spacecraft sent a large volume of findings to Dawn mission control at JPL. Later today it will again turn to point its main antenna at Earth to begin another communications session that will last for more than 30 hours. On Aug. 19, it will resume its measurements.

August 10 - Dawn Completes Mapping at Another Stereo Angle

Dawn has completed another phase of its stereo imaging of Ceres, providing more pictures to use in making a high resolution topographical map. The spacecraft transmitted its latest pictures and other data to NASA's Deep Space Network on Aug. 8-10.

For the rest of this month, the explorer will point its camera at a different angle as it photographs the dwarf planet and uses its other sensors to measure gamma ray, visible, infrared and neutron spectra.

August 3 - Dawn Conducting a Very Smooth Extended Mission

Dawn is operating flawlessly as it continues its observations of Ceres. The spacecraft is acquiring more stereo photos to improve the topographical maps and more spectra to provide insights into the dwarf planet's composition.

On July 30-31, Dawn aimed its five-foot (1.5-meter) main antenna at Earth and sent its pictures and other data. The next telecommunications session will begin shortly after 2:00 AM PDT on Aug. 4 and conclude more than 30 hours later.

July 29 - Ops Team Confirms Dawn in Good Orbit

The operations team conducted the regular assessment of Dawn's orbit and determined that it is so good, no orbit maintenance maneuvers (OMMs) are necessary. The last time an OMM was performed was June 17. Instead of ion thrusting during the OMM windows on July 31-August 1 and August 8, Dawn will continue acquiring data on Ceres.

The spacecraft began collecting data with all its sensors at this low altitude of 240 miles (385 kilometers) on Dec. 16, 2015. Tomorrow Dawn will complete its one thousandth revolution around the dwarf planet since then.

July 27 - Dawn Continues Productively in Extended Mission

Dawn is healthy and continuing to observe Ceres. The spacecraft transmitted a large volume of pictures and other scientific data to NASA's Deep Space Network on July 25-26. Dawn has sent almost 45,000 photos of the dwarf planet to Earth, and you can see a new one every weekdayhere.

The July Dawn Journal explains NASA's decision to extend Dawn's mission to explore Ceres.

July 20 - Dawn Performing More Investigations of Ceres

Since completing its last transmission of data on July 18, Dawn has been collecting more data with all of its scientific instruments as it circles dwarf planet Ceres every 5.4 hours. It will send more data to Earth on July 21 and 22.

Dawn has been in orbit around Ceres for more than 500 days. During that time, it has revealed complex and fascinating landscapes and provided scientists with a wealth of information on the alien world.

July 13 - Extended Mission Proceeding Flawlessly

Dawn is being very productive in its extended mission. It has been taking more stereo photographs (including some in color) as well as measuring spectra of Ceres in visible, infrared, gamma rays and neutrons. The spacecraft is healthy and continuing in its orbit 240 miles (385 kilometers) above the alien surface.

For readers who follow the Dawn Journal, there has been a delay for personal reasons, but don't worry: the Dawn Journals will resume soon and will continue as long as Dawn continues its ambitious and exciting mission of exploration. There is much more to look forward to!

July 6 - Dawn Exploring Ceres in Extended Mission

NASA Headquarters approved an extension of Dawn's mission at Ceres, taking advantage of the probe's capabilities to continue making discoveries about the nature of this fascinating dwarf planet.

Dawn has been acquiring more stereo images and gathering additional information with all of its spectrometers. The spacecraft began sending its latest data to Earth early this morning, and it will continue until tomorrow afternoon when it resumes its observations.

June 30 - Dawn Completes Prime Mission and Continues Observing Ceres

Today marks the official conclusion of Dawn's prime mission, which began when the spacecraft left Earth on September 27, 2007. The mission has far surpassed all of its objectives for exploring protoplanet Vesta and dwarf planet Ceres. Some interesting statistics and other information on the prime mission are here.

Dawn transmitted a large volume of scientific data to Earth on June 27-28, and it is continuing to observe Ceres even as the prime mission concludes. On July 1-2, it will transmit more pictures and spectra from its final mapping orbit at an altitude of 240 miles (385 kilometers).

June 24 - Dawn Making More Ceres Measurements

The spacecraft transmitted a large volume of Ceres measurements on June 22-23 and now is collecting even more stereo photos and spectra of the dwarf planet.

Dawn and Ceres orbit the sun together, independently of Earth. Shortly before 4:00 AM PDT today, the spacecraft was pi astronomical units from Earth, or about 292 million miles (470 million kilometers). One astronomical unit is the average distance between Earth and the sun.

June 17 - Dawn To Complete Orbit Adjustment

Dawn has had another very productive week of operations, but it has still more to do. Occasionally Dawn executes small maneuvers with its ion engine to keep the orbit synchronized with the observation plans. These orbit maintenance maneuvers (OMMs) are always performed in two windows separated by eight or nine days. The first part of the latest OMM was on June 9. Today the spacecraft will complete the OMM, this time with two thrust segments. Starting about 4:00 PM, it will use its ion engine for a little over an hour, and then it will thrust once more for 44 minutes starting shortly after 1:00 AM tomorrow. The combined effect of all three thrust segments is to change Dawn's velocity by about 0.8 mph (1.3 kilometers per hour).

Following the OMM, the spacecraft will point its main antenna at Earth to transmit more pictures and spectra. On June 19, it will resume observing Ceres.

June 14 - Dawn Stereo Mapping Proceeding Well

Yesterday and today the spacecraft transmitted its latest Ceres data to Earth. Now it is taking more stereo photos to reveal the three dimensional character of the alien landscapes. It is also continuing to acquire neutron, gamma ray, visible and infrared spectra of Ceres.

June 9 - Dawn to Adjust Orbit

Dawn started beaming more photographs and spectra to JPL yesterday, and it is continuing today.

Every three weeks, the flight team evaluates Dawn's orbit to determine whether an adjustment is needed. These "orbit maintenance maneuvers" (OMMs) were described in the February Dawn Journal. Most of the OMMs have not been necessary and so were canceled. Now a small refinement is needed, and the first part will be executed this afternoon starting shortly after 4:00 PM. Dawn will thrust with its ion engine for about an hour. The spacecraft will perform more small maneuvers on June 17 and 18.

June 6 - Dawn Operations Remain Smooth

After sending its most recent findings to Earth on June 4-5, Dawn is observing Ceres again, acquiring new photographs and spectra. The mission has already surpassed all of its original objectives for exploring the dwarf planet, and it is continuing to collect bonus data.

May 31 - Dawn Continuing to Study Ceres

Dawn is transmitting its latest pictures and spectra of Ceres to NASA's Deep Space Network.The spacecraft is healthy and all systems are working well. Early tomorrow morning it will resume observing the dwarf planet.

The May Dawn Journal explains how scientists use Dawn's photographs of craters to measure the age of geological features. It also presents some surprising information about samples on Earth from Vesta, which Dawn explored in 2011-2012.

May 26 - Dawn Completes Another Mapping Campaign

Dawn has completed the photography of the Ceres landscapes it began on April 11, pointing its camera slightly ahead and to the left. Combining pictures from that perspective with the earlier pictures looking straight down makes stereo views.

The spacecraft is now transmitting its last set of pictures and other data to Earth. After it finishes tomorrow, it will begin a new photography campaign, this time taking pictures with the camera looking slightly ahead and to the right. These pictures will form new stereo views, allowing further refinements in topographical maps of the alien terrain.

Since arriving in orbit on March 6, 2015, Dawn has now completed more than 1,000 revolutions around the dwarf planet.

May 19 - Dawn Executing All Planned Observations

Dawn is hard at work observing Ceres and storing the data in computer memory. The spacecraft is programmed to pause its measurements early on May 21, when it will turn to point its main antenna to Earth and radio the data to JPL.

Dawn is continuing to operate in "hybrid control," using its two operable reaction wheels in combination with hydrazine to control its orientation. Mission controllers activated the two reaction wheels in December when the probe reached this low altitude orbit. As long as they operate, the two wheels allow the dwindling supply of hydrazine to be used very efficiently.

May 16 - Dawn Operating Smoothly

Dawn is devoting most of today and tomorrow to sending more Ceres data to Earth.

Every three weeks, the flight team evaluates Dawn's orbit to determine whether a small adjustment maneuver with the ion engine is needed. (These "orbit maintenance maneuvers" were described in the February Dawn Journal.) Today the team concluded that the orbit is so good that no maneuver is necessary.

May 13 - Another Lucky Day for Dawn

On this Friday the 13th, Dawn is maintaining its long streak of good luck (supplemented with some skill) in exploring Ceres. The spacecraft began transmitting its most recent pictures and spectra to Earth yesterday and will finish late this morning. It will resume observing the dwarf planet around noon.

May 9 - Dawn's Fourth Mapping Orbit Continues

After beaming its latest Ceres measurements to NASA's Deep Space Network on May 7-8, Dawn is now making still more.

One year ago today, Dawn completed its first mapping orbit around Ceres at an altitude of 8,400 miles (13,600 kilometers) and began spiraling lower. A single revolution at that altitude required 15 days. Now in its fourth mapping orbit, Dawn's altitude is 240 miles (385 kilometers), and its pictures are 35 times sharper. Held tighter in Ceres' gravitational grip, Dawn travels four times faster at this lower altitude, and a single orbital loop now takes less than 5.5 hours.

May 6 - Dawn Performing Well

Dawn is completing another productive week of Ceres observations, taking pictures for topography and collecting spectra for the atomic and mineralogical composition. It will send more data to Earth on May 7-8. While pointing its camera and spectrometers at Earth, the spacecraft broadcasts a radio signal through an auxiliary antenna. That signal is used for precise tracking of Dawn's orbital motion to map the variations in Ceres' gravitational field, which provides insight into the interior structure of the dwarf planet. (All these methods of learning about Ceres have been described in recent Dawn Journals.)

May 3 - Dawn Passes Milestones at Ceres

Dawn is healthy as it continues its mission at Ceres. The spacecraft is transmitting its latest data to Earth today and tomorrow.

Dawn's orbital residence at Ceres now exceeds its time in orbit around Vesta in 2011-2012. And today Dawn's interplanetary journey has been in progress for pi thousand days. For details on these and other milestones, see the April Dawn Journal.

Five years ago today, Dawn began its approach phase to Vesta, including its first photographs of the protoplanet.

April 29 - Dawn Continues Overachieving

Dawn's exploration of Ceres is proceeding flawlessly. The spacecraft has acquired more pictures for mapping Ceres' topography as well as new infrared and nuclear spectra. It sent this large volume of data to Earth on April 28-29 and is now observing Ceres again.

The April Dawn Journal summarizes how many more measurements Dawn has accomplished at Ceres than originally planned.

April 22 - Dawn Mapping Ceres' Topography

Dawn is continuing to take pictures with its camera pointed ahead and to the left as it orbits Ceres, providing stereo views of the dwarf planet's terrain. The spacecraft will transmit its latest pictures and spectra to the Deep Space Network on April 23-24.

The operations team conducted its regular assessment of Dawn's orbit this week. They concluded the orbit was so good that an orbit maintenance maneuver was not needed.

April 18 - Dawn Gathering More Ceres Data

Dawn remains healthy in its lowest orbit around Ceres, 240 miles (385 kilometers) above the alien surface. It is taking new pictures and gathering other data as it circles Ceres every 5.4 hours. Tomorrow morning the spacecraft will begin sending all these measurements to Earth, and the next day it will start collecting even more data.

April 15 - Mapping Progressing Well

After filling its memory with more observations of Ceres, Dawn began transmitting its results to Earth yesterday afternoon. Tonight it will resume studying the dwarf planet.

April 11 - Dawn Beginning New Ceres Mapping

Dawn is taking pictures and collecting spectra of Ceres. It is now pointing its camera and other instruments slightly ahead and to the left as it circles the dwarf planet. With pictures taken at an angle, scientists will have stereo views so they can construct a more detailed topographical map than they developed in the third mapping orbit. (The March Dawn Journal and the links there explain the stereo imaging in more detail.)

On April 9-10, Dawn maneuvered with its ion engine to synchronize its orbit with the plan for observing Ceres. (These orbit maintenance maneuvers are described in the February Dawn Journal.) Then on April 10-11, it pointed its main antenna to Earth to radio its latest observations to the planet where its journey began.

Dawn's main computer is using software controllers installed five years ago this week, shortly before the spacecraft arrived at Vesta. And exactly two years earlier, they also loaded new software. (Follow the link to find out how you can get a copy of the software for your own use, or simply put your computer or smartphone in the main asteroid belt, send us the coordinates, and we'll install it for you.)

April 8 - Dawn to Execute Small Maneuver This Weekend

Dawn is continuing to observe Ceres. Tomorrow it will begin the second half of the orbit maintenance maneuver it performed on April 1 and 2. It will thrust with ion engine #2 for almost two hours starting about 3:30 PM and then again for almost 2.5 hours beginning shortly before 11:00 PM.

After it completes the maneuvering on April 10, the spacecraft will use its main antenna to establish contact with the Deep Space Network and transmit all the data it collected since the last communications session on April 6.

April 5 - Dawn Healthy and Operating Well

Since thrusting with its ion engine on April 1 and 2 to refine its orbit around Ceres, Dawn has been collecting more data on the dwarf planet. It is taking pictures, measuring the gravity field, and collecting infrared, gamma ray and neutron spectra. Shortly after 9:30 AM PDT today, the spacecraft will turn its sensors away from Ceres to point its 5-foot (1.5-meter) antenna to Earth. It will resume its scientific observations by 1:30 PM tomorrow.

April 1 - Dawn to Adjust Orbit

At the end of another productive week, Dawn is transmitting its most recent scientific data to the Deep Space Network . The March Dawn Journal presents some of the mission's latest findings about Ceres.

The spacecraft will start executing an orbit maintenance maneuver (OMM) shortly after 5:00 PM PDT today. It will thrust with its ion engine for a little more than two hours, and then about 1:00 AM PDT on April 2 will begin thrusting again for the same duration. Following that, Dawn will resume its observations of Ceres. The second half of the OMM will consist of two more thrust segments on April 9-10. (OMMs are explained in more detail in the February Dawn Journal.)

March 29 - Operations Team Verifying Dawn's Orbit

As Dawn continues its exploration of Ceres, the operations team is conducting its regular evaluation of the spacecraft's orbit around the dwarf planet. The probe has been doing an excellent job collecting data, but small deviations from the planned orbit gradually accumulate. Occasionally the ion engine is used to perform an "orbit maintenance maneuver," as explained in the (February Dawn Journal.)The team will decide this week whether to adjust the orbit.

Today is the 209th anniversary of the discovery of Vesta. When Heinrich Wilhelm Matthäus Olbers first spotted it, he could hardly have imagined that a ship from Earth would travel to that mysterious point of light among the stars. And yet Dawn did, and it provided a detailed and richly rewarding exploration of the world that Olbers found.

March 25 - Dawn Making New Observations

Dawn is operating flawlessly as it acquires more photos and spectra of Ceres. The explorer transmitted its findings to Earth on March 23-24, and it will send the data it is collecting now on March 27-28.

March 22 - Dawn Revealing New Sights

Dawn is healthy and continuing its observations of Ceres. After transmitting data to Earth on March 18 and 19, the spacecraft began a new set of measurements. Now, instead of looking straight down, it is pointing its sensors a little bit to the left as it circles Ceres. This provides a slightly different perspective on the alien landscape and may reduce the rate at which the probe consumes its dwindling hydrazine propellant. (Hydrazine is essential for Dawn's operation.)

A new view of the famous bright area in Occator crater, photographed by Dawn from the closest it will ever come to the intriguing geological feature, is now available here.You can see other new Ceres images based on Dawn's measurements at the Ceres image gallery.

March 18 - Dawn Concluding Another Week of Observations

After spending most of the week observing Ceres, Dawn paused this morning to point its main antenna at Earth. It is now radioing its precious data to the Deep Space Network. It will resume its measurements tomorrow around noon.

March 15 -Dawn Maintaining Its Productive Exploration Routine

With its suite of sensors pointed at the alien landforms 240 miles (385 kilometers) beneath it, Dawn is collecting more data as it orbits Ceres. It sent its latest findings to Earth on March 13 and 14.

March 11 -Dawn Continuing to Observe Ceres

Dawn is healthy and all systems are operating well as it takes more pictures and acquires more neutron, gamma ray and infrared spectra of Ceres.

On March 13, it will pause its observations to transmit the most recent data to Earth.

Dawn arrived in orbit on March 6, 2015, a historic culmination of an extraordinary interplanetary journey. The explorer began extensive photography of Ceres and measurements of infrared and visible spectra even before Ceres' gravity took hold. The spacecraft's gamma ray and neutron detector was activated on March 12, 2015, even though scientists understood that its detailed measurements would not begin until reaching this low altitude.

March 9 -Orbit Maintenance Maneuvers Deemed Unnecessary

Dawn is aiming its main antenna at Earth, transmitting its latest photos and other measurements of Ceres. It will resume collecting data this afternoon.

As the flight team was working on the details of the orbit maintenance maneuvers described in the March 7 status report, they determined that the current orbital parameters are satisfactory. Therefore, rather than take the spacecraft's time away from observing Ceres to perform the maneuvers to achieve a small improvement in the orbit, they have decided to let it continue to point its sensors at the dwarf planet without these interruptions.

March 7 -Dawn to Adjust Its Orbit

Dawn's exploration of Ceres is continuing to go extremely well. As explained in the February Dawn Journal, the flight team occasionally needs to adjust the spacecraft's orbit to keep it synchronized with the intricate plans for observing the dwarf planet. They have now determined that Dawn should perform a set of "orbit maintenance maneuvers" for this purpose. Mission controllers are now working on the details to send to the spacecraft, and it will use its famously efficient ion engine to thrust for almost 1.5 hours on March 9, then wait for 6.5 hours and then thrust again for shortly over an hour on March 10. It will perform two additional maneuvers on March 17 of just over an hour and just under an hour, with two hours between them.

March 4 -Dawn at Maximum Distance from Earth

As Dawn continues exploring Ceres, today it is at its greatest distance from Earth for the entirety of its extraordinary extraterrestrial expedition. It is more than 3.95 AU (367 million miles, or 591 million kilometers) from its original planetary home. Details and a diagram are in the February Dawn Journal.

Dawn will spend much of today and tomorrow radioing data to mission controllers. It will take the signals almost 33 minutes to travel from the spacecraft to Earth. The probe will resume its scientific observations early tomorrow afternoon.

February 29 -Dawn Surpasses Its Objectives

Dawn is transmitting its latest pictures and spectra to NASA's Deep Space Network today. Shortly before midnight tonight, the spacecraft will turn to point its sensors at Ceres again and resume its observations.

Dawn's long interplanetary adventure to explore two of the last uncharted worlds in the inner solar system has been extremely productive. The probe has successfully completed all of the measurements it was designed to make, fulfilling the objectives set for it many years ago. Nevertheless, it will continue to acquire data as it orbits the distant dwarf planet. For details, see the February Dawn Journal.

February 26 -Dawn Sends Back More Valuable Observations

Dawn is wrapping up another good week in its final mapping orbit at Ceres. On Feb. 24-25, it returned a wealth of data including photos, nuclear spectra from its gamma ray and neutron detector and infrared spectra from its visible and infrared mapping spectrometer. It is collecting still more data now, which it is scheduled to send to Earth on Feb. 28-29.

February 22, 2016 -Dawn's Exploration Continuing Smoothly

Orbiting Ceres at about 610 mph (980 kilometers per hour), Dawn circled the dwarf planet five times on Feb. 19-20 with its main antenna aimed at Earth, sending pictures and spectra to NASA's Deep Space Network. Following that, it returned to pointing its sensors at the ground beneath it and has been acquiring more data since then.

February 19, 2016 -Dawn Maintaining Productive Pace of Operations

Dawn has been collecting more data on Ceres this week with its camera and spectrometers, and all systems are working well. It will begin transmitting the results to Earth shortly before 1:00 PM PST today. The probe will resume observing Ceres a little after 4:00 PM tomorrow.

February 16, 2016 -Dawn Working Well at its Fourth Planetary Body

After spending much of Feb. 14 and 15 beaming data to Earth, Dawn is back to photographing Ceres and making other measurements.

Tomorrow is the seventh anniversary of Dawn flying past Mars, robbing the Red Planet of some its orbital energy around the sun in order to help fling the spacecraft on its way to more distant and exotic destinations. Dawn achieved a cosmic bull's-eye in gaining that gravitational boost. The equivalent change in the spacraft's speed was 5,800 mph (9,400 kilometers per hour). In exchange Mars slowed down by a rate of one inch (2.5 centimeters) per 180 million years to keep the solar system's energy account balanced. Dawn has been to four planetary bodies, starting on Earth in 2007, sailing past Mars in 2009, orbiting protoplanet Vesta in 2011-2012, and residing since last year at dwarf planet Ceres, its final home.

February 12, 2016 -Dawn Observing Ceres from its Planned Orbit

Dawn transmitted another large volume of Ceres measurements to JPL via the Deep Space Network on Feb. 10 and 11. Now it is back to observing the dwarf planet, collecting more data, which it will send to Earth on Feb. 14 and 15. Also on Feb. 14, controllers will send new instructions for continuing the program of exploration. We love Dawn, but that goes without saying, so no Valentine's sentiments will be included in the interplanetary messages.

Approximately every three weeks, the flight team analyzes the spacecraft's orbit to determine whether to adjust it with the ion engine. (We mentioned this in the mission status reports on Jan. 19 and 21, and the February Dawn Journal will include an explanation.) Based on their latest assessment, Dawn's orbit continues to be so good that no minor corrections are warranted. The present orbital parameters match very well with the plans for new pictures and spectra. This is the second time in a row that "orbit maintenance maneuvers" were deemed unnecessary.

February 8, 2016 -Dawn Continuing to Study Ceres

Aiming its suite of sophisticated sensors at the ground below, Dawn is orbiting closer to Ceres than the International Space Station is to Earth. The explorer is healthy and continuing to perform all of its duties.

February 5, 2016 -Dawn Seeing More and More of Ceres

Dawn is gathering more Ceres data, circling the dwarf planet every 5.4 hours with its combined gamma ray and neutron detector, infrared mapping spectrometer and camera pointed at the landscapes beneath it. Meanwhile, it is transmitting a broad radio signal through one of its auxiliary antennas so we can track its orbital motion to improve measurements of Ceres' gravity field. Shortly after 9:00 PM PST today, the spacecraft will begin sending its results through its main antenna to Earth.

Dawn has photographed about 90% of Ceres from this low altitude orbit. Many people who share our fascination with that distant alien world ask about new pictures of the famous bright area (or famously bright area) at the center of Occator crater, but Dawn has not observed it yet. That is just the way the orbit has worked out. Mission planners did not design the orbit or the schedule of observations and telecommunications to view any specific targets. Rather, as mentioned in the January Dawn Journal, the team designed them so that over the course of six weeks, the probe would see most of the surface. As we will see in the February Dawn Journal, the first few weeks of LAMO don't contribute to this pattern, so the beginning of the six week period was January 10. By simple coincidence, Dawn will not have the opportunity to see Occator until the very end of that period. Therefore, we all wait patiently. After Occator is photographed, the standard process for releasing images will be followed. The need for accuracy and scientific review of the data sometimes slows the release of some products, but all of the data are released to the public after the science team has performed the necessary analysis and interpretation for scientific publication. It will be worth the wait!

February 1, 2016 -Dawn Mapping Proceeds Flawlessly

Dawn continues to operate flawlessly in its final mapping orbit around Ceres. The spacecraft is pointing its main antenna at Earth today, transmitting its latest pictures and other data. It will resume its observations tomorrow shortly before 10:00 AM PST.

The latest Dawn Journal describes some of the measurements Dawn is making to reveal the nature of the first dwarf planet discovered.

January 25, 2016 -Dawn's High Resolution Observations Continue

After concluding its telecommunications session on Jan. 23, Dawn brought Ceres back into its sights. It has been collecting more data since then as it circles the dwarf planet at an average altitude of 240 miles (385 kilometers).

One year ago today, the spacecraft was 147,000 miles (237,000 kilometers) from Ceres, using its ion engine to approach the alien world. Later in the day, it took its second set of pictures to navigate to the uncharted destination. Those were its photos to surpass the resolution provided by the Hubble Space Telescope. Now Dawn's sharp pictures show about 830 times the detail that Hubble's images revealed. The Jan. 29, 2015, Dawn Journal described the navigation pictures and even looked ahead to the improvement we would achieve in the current low altitude orbit. The last year has been a fantastic period of discovery.

January 21, 2016 -Dawn Collecting Data with Good Orbital Accuracy

Dawn remains healthy and productive, taking photos and spectra of Ceres. It will continue doing so until Jan. 22, when it is scheduled to transmit more of its precious data to Earth.

The spacecraft's orbit around the dwarf planet is close enough to what mission planners had specified for this period that it is not necessary to perform the pair of orbit maintenance maneuvers described in the Jan. 19 mission status update. Instead, the spacecraft will continue pointing its sensors at Ceres during the windows that were scheduled for the maneuvers. The next decision on whether to perform orbit maintenance maneuvers will be in three weeks.

January 19, 2016 -Dawn About to Resume Observing Ceres

The spacecraft spent the weekend filling its computer memory with more Ceres data, and it has been sending those findings to NASA's Deep Space Network since yesterday morning. Shortly after noon PST today, it will resume its observations.

Meanwhile, the flight team is using the latest navigational measurements to determine Dawn's orbit very accurately and calculate what it will be for the next few weeks. Based on these and other analyses, the mission director will decide tomorrow whether Dawn should perform an orbit maintenance maneuver. If so, mission planners already have windows in Dawn's intricate schedule on Jan. 23-24 and Jan. 31-Feb. 1. (Orbit maintenance maneuvers in this low altitude orbit are always done in pairs separated by about eight days.)

January 15, 2016 -Dawn Maintaining its Productive Pace

Dawn used its main antenna for about 26 hours on Jan. 13 and 14 to transmit a wealth of data to Earth. Now the spacecraft is taking more photographs and other scientific measurements while orbiting about 240 miles (385 kilometers) above Ceres’ surface.

Dawn is healthy and continuing to operate smoothly. The two reaction wheels that were activated on Dec. 14 have been functioning well, and the consumption of hydrazine propellant (used in combination with the reaction wheels to control the probe's orientation) is very good.

January 11, 2016 -Dawn Hard at Work Observing Ceres

After completing its orbit maintenance maneuver on Jan. 8, Dawn spent much of the weekend with its main antenna aimed at Earth as it revolved around Ceres, beaming its latest data to NASA's Deep Space Network. Then around 9:00 AM PST on Jan. 10, the spacecraft turned to point its science instruments at the ground beneath it and resumed its program of observations of the dwarf planet. It will continue until 7:00 PM PST on Jan. 13, when it is scheduled once again to start transmitting the precious measurements stored in its memory.

January 8, 2016 -Dawn to Perform Small Orbit Maintenance Maneuvers

After devoting much of the week to observing Ceres, Dawn will execute a pair of burns with its ion engine today to modify its orbit. Starting a little after 1:00 PM, the ship will thrust for less than two hours, wait about six hours as it continues to revolve around Ceres and then thrust again for less than two hours, finishing around 11:00 PM. With its uniquely efficient and gentle ion engine, these small orbit maintenance maneuvers will keep the explorers' orbital motion aligned with the plan the flight team has devised for systematically studying the alien world from this low orbital altitude of 240 miles (385 kilometers). Dawn will spend most of the weekend sending its pictures and other data to Earth. When it has finished on the morning of Jan. 10, it will begin collecting still more data.

January 4, 2016 -Dawn Concludes a Productive New Year's Weekend

After using its ion engine for almost 11 hours on Dec. 31 - Jan. 1 to adjust its orbit slightly, keeping it synchronized with the plan for mapping Ceres, the spacecraft resumed its observations. Since then, it has been taking more pictures and measuring spectra of infrared light and two kinds of nuclear radiation. It has also been sending a radio signal that engineers and scientists use to track its orbit in order to map the interior structure of the dwarf planet. (The radiation and orbit measurements are explained in the most recent Dawn Journal.)

This afternoon the spacecraft will turn to point its main antenna to Earth and then spend about a day transmitting its latest results. Tomorrow afternoon it will turn once again to aim its sensors at the rocky, icy ground and collect more data until its next pause on Jan. 8

December 31, 2015 -Dawn Busy as Year Ends

Dawn is transmitting its latest Ceres observations, orbiting the dwarf planet while pointing its main antenna to Earth. This afternoon the spacecraft will use its ion engine to perform an orbit maintenance maneuver, which will keep its orbit matched with the plan for obtaining good coverage of the world beneath it. Following that, the probe will turn again to point its instruments at Ceres and resume collecting data.

The December Dawn Journal describes the highest priority scientific observations Dawn is conducting in this fourth and final mapping orbit.

December 29, 2015 -Flight Team Preparing Small Adjustment to Orbit

Dawn remains in good health as it continues to take pictures and make other measurements of Ceres. As at Vesta, occasional small adjustments to its orbital motion will be required at this low altitude to keep it synchronized with the observing plan. The flight team is working on the detailed flight plan for the first of these "orbit maintenance maneuvers," scheduled for Dec. 31.

December 23, 2015 -Dawn Observing Ceres Again

Dawn sent its latest measurements to mission control at JPL as it completed five revolutions around Ceres, each lasting about 5.4 hours. Around 11:30 p.m. PST on Dec. 22, it once again aimed its scientific instruments at the rocky, icy surface beneath it and began collecting more data.

December 21, 2015 -New Mapping Proceeding Smoothly

Since Dec. 18, Dawn has been taking neutron spectra, infrared spectra, gamma ray spectra, and photographs of Ceres from the lowest altitude orbit. As the spacecraft revolves around the dwarf planet, it points its sensors at the ground but also switches among its auxiliary radio antennas to use whichever is pointed closest to Earth. That allows engineers and scientists to use the radio signal to measure the orbital motion very accurately to map the gravity field.

Tonight Dawn will turn to point its main antenna to Earth for more than 27 hours. Tomorrow night, after transmitting most of its pictures and other data, it will resume observing Ceres.

December 18, 2015 -Dawn Ready for More Observations of Ceres

While Dawn was taking preliminary pictures and infrared spectra on Dec. 16-17, the flight team was putting the finishing touches on commands the probe will use for further observations that start later today. After the trajectory correction maneuver that completed on Dec. 13, navigators measured Dawn's orbital parameters very precisely. Combined with their latest measurements of Ceres' gravity field, they formulated a new prediction of Dawn's orbital motion over the coming weeks. The detailed plans for observing the dwarf planet then were adjusted to account for this latest information.

December 16, 2015 -Dawn Begins Photography and Infrared Spectroscopy

Dawn is now taking pictures and infrared spectra of Ceres from its new average orbital altitude of 240 miles (385 kilometers). In this fourth and final mapping orbit, the pictures will be four times sharper than those from the previous mapping orbit. Nuclear spectroscopy and gravity measurements began last week upon arrival at this low orbit.

The JPL flight team is continuing to incorporate the latest orbital parameters into the plans for the more intensive observations that will start on Dec. 18.

On Dec. 14, mission controllers activated Dawn's two operable reaction wheels to help conserve hydrazine propellant for pointing and turning the spacecraft. The plan to keep the wheels off until now was devised in 2013 following the failure of the other two wheels in 2010 and 2012. Since then, the wheels have been powered on only for a test of the current control scheme (explained in the November 2013 Dawn Journal) and routine maintenance. They are performing well, but engineers understand that the other two gave no indications of any problems until immediately before they faltered. As long as the wheels do function, they will provide a bonus reduction in hydrazine use.

December 14, 2015 -Dawn Preparing for New Observations

Dawn thrust with its ion engine on Dec. 11-13 to fine tune its orbit. When it finished, it pointed its gamma ray and neutron detector (GRaND) at Ceres. GRaND measures the energies and numbers of these two components of nuclear radiation, from which scientists can determine the abundances of some elements on the dwarf planet.

Navigators are making precise measurements of the adjusted orbit to verify that it meets the needs for the intensive observation campaign that will begin on Dec. 18. In the meantime, the spacecraft will collect more radiation measurements as well as conduct some bonus photography and infrared spectroscopy on Dec. 16-17.

Later today mission controllers will power on two of Dawn's reaction wheels. (Two others failed in 2010 and 2012.) Engineers cannot confidently predict how long the two units will operate, but as long as they do, they will reduce the expenditure of hydrazine propellant, extending the spacecraft's lifetime in this final phase of the mission. When either one fails, Dawn will return to using only hydrazine to control its orientation. (The November Dawn Journal explains this in more detail.)

December 11, 2015 -Dawn Ion-Thrusting to Adjust Orbit

Dawn is now using its ion engine to adjust its orbit. This maneuver (explained in the November Dawn Journal.) will synchronize the spacecraft's orbital motion with Ceres' rotation around its axis to fit with the plan for the extensive observations that will begin next week.

Yesterday while the flight team was preparing Dawn's flight plan, the spacecraft tested its backup camera. Controllers occasionally run the camera through a series of tests to verify that it remains in good condition should the primary camera have a problem. (The test of the camera was performed eight years to the day after its first operation in space.) Although the results have not been analyzed in detail yet, all indications are that the backup is in excellent condition.

December 9, 2015 -Dawn at Lowest Orbital Altitude at Ceres

Dawn completed ion-thrusting on schedule on Dec. 7 and continues to be healthy and operating well in its new orbit. Over the last two days, the flight team has determined that the spacecraft did an excellent job in maneuvering to its planned orbit at an average altitude of 240 miles (385 kilometers). To match Dawn's orbital motion with the intricate plan for observing Ceres, the probe will use its ion engine to perform a small adjustment (known as a "trajectory correction maneuver") to the orbit. Long before the spiral descent began, engineers had calculated that such a maneuver was likely and already had a window planned for this purpose on Dec. 11-13. (This was described in the November Dawn Journal.) They are now developing the detailed flight plan for the spacecraft.

December 7, 2015 -Dawn to Stop Ion-Thrusting Today in Low Altitude Orbit

Dawn is scheduled to conclude ion-thrusting for its spiral descent shortly before noon today. At that time, it will be orbiting about 240 miles (385 kilometers) above Ceres, closer than the International Space Station is to Earth. After it turns to point its main antenna to Earth, navigators will begin to measure its orbital parameters very accurately. During the next two days, they will analyze the orbit carefully and decide on Dec. 9 whether to make an adjustment at the end of the week. (It is likely such a trajectory correction maneuver will be needed.) The November Dawn Journal explains this in more details.

December 4, 2015 -Dawn Closing in on Final Mapping Orbit

Dawn has now reduced its orbital altitude to 270 miles (435 kilometers). The probe is continuing to make excellent progress to its fourth and final mapping orbit.

November 30, 2015 -Dawn Continuing to Thrust to Lowest Ceres Orbit

Dawn is now less than 300 miles (480 kilometers) from the alien world of ice and rock. This last major ion-thrusting period of the mission has been going very smoothly, and the spacecraft will reach its targeted altitude of 240 miles (385 kilometers) next week.

This month's Dawn Journal includes an overview of the plans for when Dawn arrives in its lowest altitude orbit around Ceres.

November 25, 2015 -Dawn Making Good Progress to Lower Altitude

During this spiral descent from the third mapping orbit to the final one, Dawn has paused ion thrusting on Thursdays so JPL mission controllers can transmit an updated flight plan. To give the flight team time off for Thanksgiving, the operations schedule has an update today instead of tomorrow. So this afternoon Dawn will stop thrusting and rotate to point its main antenna to Earth.

The tireless explorer will not take the holiday off. It will spend Thanksgiving using its ion propulsion system to reduce its orbital altitude. It will be thankful that on Nov. 26, its average altitude will be 335 miles (537 kilometers), so it will only have to lower its orbit by about 100 miles (160 kilometers) more.

November 23, 2015 -Dawn's Maneuvering Proceeding Well

As Dawn continues to lower its orbit, today its average altitude is about 355 miles (570 kilometers). At this height, each revolution around Ceres takes about 7.5 hours.

November 20, 2015 -Dawn Reaching Ever Closer to Ceres

Dawn's average altitude today is about 395 miles (635 kilometers). The spaceship is orbiting Ceres at 530 mph (855 kilometers per hour).

Once a week during its spiral descent, Dawn stops ion thrusting so it can point its main antenna at Earth. When it did so on Nov. 19, the JPL flight team transmitted the latest flight plan, which incorporated updates using the navigation data collected one week earlier. (See the Nov. 13 status update.)

November 16, 2015 -Spiral Descent Continuing Smoothly

Dawn's ion engine is continuing to push it to lower orbits. Today the spacecraft's average altitude is about 445 miles (715 kilometers).

All of Dawn's ion thrusting throughout its interplanetary journey of more than eight years has now provided the equivalent of 24,500 mph (39,400 kilometers per hour), far more than any spacecraft has achieved with its own propulsion system. Because of the principles of motion for orbital flight, whether around the sun or any other gravitating body, Dawn is not actually traveling this much faster than when it launched. See here for an explanation of this curious phenomenon.

As Earth and Ceres (carrying its sole companion, Dawn) travel on their own independent orbits around the sun, the distance between them is constantly changing. This morning they were pi astronomical units (292.0 million miles, or 469.9 million kilometers) apart. They are separating at almost 52,000 mph (83,000 kilometers per hour).

November 13, 2015 -Dawn Progressing to Lower Altitude

Today Dawn's average altitude is about 490 miles (790 kilometers).

Following its weekly pattern, Dawn stopped ion thrusting yesterday afternoon to aim its main antenna at distant Earth. The flight team at JPL transmitted an updated flight plan for the descent spiral, and Dawn sent a detailed report on its activities and health during the previous week. In addition, accurate tracking of the radio signal as the spacecraft flew around Ceres provided navigators with new data to calculate the orbit. They will incorporate the results into next week's update.

The only probe from Earth ever to take up permanent residence in the main asteroid belt between Mars and Jupiter, Dawn has now been in that part of the solar system for six years.

November 9, 2015 -Dawn Lowering its Orbit

More than three times as far from Earth as the Sun is, Dawn is using its ion propulsion system to maneuver to its final orbit around Ceres. The spacecraft's average altitude above the alien world today is about 550 miles (885 kilometers).

As Dawn descends, the time to complete one revolution gets shorter, both because the velocity increases and because the distance around an orbit decreases. Today it is 11 hours. In the third mapping orbit, each revolution required 19 hours.

November 5, 2015 -Dawn Descending on Course and on Schedule

As Dawn spirals to lower orbits, its average altitude today is about 620 miles (1000 kilometers). Each week, controllers update the complex flight plan for ion thrusting, so Dawn will pause thrusting this afternoon, turn to point its main antenna to Earth to receive its new instructions, and resume thrusting tonight. Tomorrow the spacecraft will reach to below 600 miles (966 kilometers).

November 2, 2015 -Ion Thrusting to Lower Orbit Continues

Dawn has reduced its average altitude today to about 680 miles (1100 kilometers) as it maneuvers to its final orbit. Because lower orbits require higher velocity (to balance the stronger gravitational pull), the spacecraft is now orbiting the dwarf planet at about 450 mph (725 kilometers per hour). (Orbital velocity in the third mapping orbit, which concluded on Oct. 23, was about 400 mph, or 645 kilometers per hour.)

October 30, 2015 -Dawn's Spiral Descent Proceeding Well

Dawn is continuing to use its ion propulsion system for the gradual descent from the third mapping orbit to the fourth and final mapping orbit. Today the spacecraft's average altitude is about 750 miles (1205 kilometers).

The October Dawn Journal summarizes some of the accomplishments in Dawn's extremely productive third mapping orbit, which concluded last week.

October 26, 2015 - Dawn Maneuvering to Lower Orbit

On Oct. 23, when Dawn was orbiting at an altitude of 915 miles (1,470 kilometers), it started more than seven weeks of ion thrusting to lower its orbit to less than 235 miles (380 kilometers). Today the spacecraft's average altitude is 835 miles (1,345 kilometers).

October 23, 2015 - Dawn To Begin Final Spiral Descent

Dawn has finished transmitting its extensive observations of Ceres to Earth.

About 3:30 p.m. PDT today, the spacecraft will fire up ion engine #2 to start maneuvering to its final orbital altitude. It will take more than seven weeks to spiral down from 915 miles (1,470 kilometers) to less than 235 miles (380 kilometers).

The August 2014 Dawn Journal provided an overview of the plans for the explorer's final mapping orbit at Ceres.

October 21, 2015 - Dawn Completes Topographical Mapping

This morning Dawn conducted its final observations from its current orbital altitude of 915 miles (1,470 kilometers). Following the 12th flight over Ceres' sunlit hemisphere in its sixth mapping cycle in this orbit, the spacecraft rotated to aim its main antenna to Earth. It is now beaming its pictures and spectra to NASA's Deep Space Network.

Next week's Dawn Journal will include a summary of this extremely productive third mapping campaign, which began on Aug. 17.

Ion thrusting to spiral down to the fourth and final orbital altitude will begin on Oct. 23.

October 19, 2015 - Final Mapping Cycle Continuing Smoothly

Dawn is flying over the lit hemisphere of Ceres for the 10th time in the final mapping cycle, taking pictures and measuring spectra. After it completes the 12th revolution on Oct. 21, it will turn to point its main antenna to transmit the data to Earth.

October 16, 2015 - Dawn Halfway Through Sixth Mapping Cycle

This morning Dawn completed observations during its sixth transit over the dayside of Ceres in mapping cycle #6. The spacecraft is continuing to operate extremely well.

The flight team is now developing the detailed flight profile and the associated instructions the probe will follow for its spiral descent from this third mapping orbit to the fourth and final orbit, which it will reach in December. Ion thrusting is scheduled to begin on Oct. 23.

October 12, 2015 - Final Mapping Cycle Underway

Dawn transmitted the last of its measurements from mapping cycle #5 yesterday and started its sixth mapping cycle today at 1:40 a.m. PDT. Mapping cycle #6 will consist of 12 flights over the sunlit terrain, during which the explorer will aim its sensors at the scenery farther behind than in the third mapping cycle but not as far to the right. The pictures will add to scientists' determination of the topography of this alien world. This will be the last set of observations made at the current altitude of 915 miles (1,470 kilometers).

October 9, 2015 - Fifth Mapping Cycle Wrapping Up

Dawn will start its 12th and final passage in mapping cycle #5 over the dayside of Ceres this afternoon. After completing these observations at 1:31 a.m. PDT tomorrow, the spacecraft will aim its main antenna to Earth. It will take about two days to radio all of its photos and other data to NASA's Deep Space Network. Dawn will orbit Ceres 2.5 times while it is transmitting its findings.

The final mapping cycle in this phase of the mission will begin on Oct. 12.

October 5, 2015 - Fifth Mapping Cycle Half Complete

Dawn conducted its sixth observing session in mapping cycle #5 today, spending more than nine hours photographing Ceres and collecting more spectra.

Since entering orbit in March, Dawn has completed more than 100 revolutions around the dwarf planet, with 62 of those occurring since the start of this third mapping phase on Aug. 17.

October 1, 2015 - Dawn Begins Fifth Mapping Cycle

After sending the last of its data from the fourth mapping cycle to Earth, Dawn started its fifth mapping cycle on Sep. 30 at 11:40 p.m. PDT. During this 11-day period, the tireless explorer will aim its sensors toward the terrain immediately ahead as it orbits the alien world at an altitude of 915 miles (1,470 kilometers). This new angle will provide scientists with another stereo view to use in developing 3-D perspectives.

This morning Dawn completed the first transit in this cycle over the side of Ceres facing the sun. The dwarf planet turns on its axis in nine hours, and the spacecraft revolves around it in 19 hours, spending half that time over the sunlit landscape and half over the ground hidden in the dark of night. With 12 orbital loops, Dawn's camera can see all of the terrain.

September 28, 2015 - Fourth Mapping Cycle Nearly Complete

This afternoon Dawn will begin the 12th and final observation session in its fourth mapping cycle. Upon completing this last flight over the illuminated hemisphere, the spacecraft will point its main antenna at Earth for two days to transmit the many pictures and spectra it has acquired.

On Sep. 27, Dawn celebrated its eighth anniversary of being in space. This month's Dawn Journal looks at the spaceship's progress on its interplanetary travels.

September 25, 2015 - Dawn Conducting Fourth Mapping Cycle

Dawn has completed more than half of its fourth mapping cycle, acquiring more stereo pictures as well as spectra in infrared and visible wavelengths. Today the ship will make its eighth transit over the hemisphere of Ceres lit by the sun.

September 21, 2015 - Dawn Conducting Fourth Mapping Cycle

Dawn began its fourth mapping cycle on Sept. 19 at 10:13 p.m. PDT. The probe has now completed two of the 12 revolutions needed to photograph the dwarf planet's entire surface.

For this mapping cycle, the spacecraft points its camera and spectrometers at the scenery ahead and to the left as it orbits at an altitude of 915 miles (1,470 kilometers). Together with the pictures from the other mapping cycles, the different views will allow scientists to develop topographical maps. The visible and infrared mapping spectrometers, which observe a smaller area than the camera, are continuing to study previously unobserved regions with each new mapping cycle.

September 18, 2015 - Observations for Third Mapping Cycle Complete

Dawn completed the observations for the last of its 12 flights over the dayside of Ceres at 12:32 a.m. PDT. It then rotated to point its main antenna to Earth and is now beaming its pictures and infrared and visible spectra to Earth.

The fourth mapping cycle will begin on Sept. 19.

September 14, 2015 - Third Mapping Cycle More Than Half Complete

On Sept. 13, during the seventh transit over the dayside of Ceres in the third mapping cycle, the computer in the camera detected an unexpected condition in the camera and turned off. Engineers observed the situation not long afterwards when Dawn was over the night side of Ceres. In preparation for the next dayside observations, they returned the camera to its normal configuration and confirmed it is healthy.

Today Dawn will observe terrain in the illuminated hemisphere of Ceres for the eighth time. The spacecraft revolves around the dwarf planet every 19 hours, so the twelfth and final dayside pass for this cycle will conclude on Sept. 18.

September 11, 2015 - Dawn Continuing to Map Ceres

Dawn is making good progress on photographing Ceres for its third map. It is also acquiring a wealth of spectra at infrared and visible wavelengths. Today the explorer is making its fourth passage over the lit hemisphere.

September 8, 2015 - Third Mapping Cycle Commences Tonight

Dawn is completing transmission to Earth of the pictures and spectra it acquired during its second mapping cycle while orbiting Ceres at an altitude of 915 miles (1,470 kilometers).

The robotic explorer will begin its third mapping cycle at 12:12 a.m. PDT on Sept. 9. During each of its 12 flights over the dayside of Ceres, it will point its camera and spectrometers behind and to its right, providing a third perspective on the landscape for use in developing topographic maps.

September 4, 2015 - Second Mapping Cycle Going Smoothly

Today Dawn is making its ninth transit over the illuminated hemisphere of Ceres in its second mapping cycle. Throughout this cycle, it is taking pictures and making spectral measurements of the terrain behind and to its left as it orbits the dwarf planet.

The spacecraft will complete its observations for this second map shortly before 1:00 a.m. PDT on Sept. 7. It will then spend almost two days (about 2.5 revolutions around Ceres) transmitting its results to NASA's Deep Space Network.

August 31, 2015 - Dawn's Second Mapping Cycle Underway

Orbiting Ceres at an average altitude of 915 miles (1,470 kilometers), Dawn is photographing the dwarf planet for a new map. Each map requires observations during 12 flights over the dayside of Ceres (plus two more while it transmits the pictures and spectra to Earth). The team calls this one "cycle." (See the August Dawn Journal for more on how the mapping works.)

Today the spacecraft is making its fourth flight over the dayside of Ceres in the second mapping cycle.

August 27, 2015 - Dawn Completes First Mapping Observations

Shortly before midnight last night, Dawn completed its twelfth revolution over the sunlit side of Ceres in this mapping phase. That concluded the observations required to make the first map.

The spacecraft is now pointing its main antenna to Earth and transmitting its precious results. It will continue sending pictures and other data until tomorrow night.

Dawn will begin its second mapping cycle at this altitude around 11:00 PM PDT on August 28. As explained in the Dawn Journal, throughout the second mapping observations, it will point its camera a little back and to the left, rather than straight down, providing provide stereo views from which scientists can construct 3-D views of the alien terrain.

August 24, 2015 - Mapping Proceeding Extremely Well

Today Dawn is making its ninth orbital passage over the illuminated side of Ceres since beginning its new mapping phase. The explorer needs 12 dayside passes (each lasting 9.5 hours, or half an orbit) to see all of Ceres. (This is explained further in the latest Dawn Journal.)

August 21, 2015 - Dawn's New Mapping Phase Off to a Smooth Start

Dawn is performing flawlessly as it takes pictures and collects other data in its new orbit. The spacecraft's view is now three times as sharp as in its previous mapping orbit, which concluded in June.

At this orbital altitude, it takes Dawn 11 days to photograph all of Ceres and transmit the data to Earth. The probe is scheduled to map Ceres six times over the next two months. The latest Dawn Journal includes a description of the plans for this phase of the exploration of Ceres.

August 17, 2015 - Third Mapping Campaign to Begin Tonight

The mission control team has now provided Dawn with accurate knowledge of its orbit parameters. They have also completed transmitting all of the other information it needs and confirmed that the explorer is ready for its new Ceres mapping campaign.

Dawn has been pointing its main antenna to Earth since Aug. 13. Shortly after 9:00 pm PDT today it will start rotating to point its camera and other sensors at the landscape below and will begin taking pictures over the north pole less than an hour later.

August 13, 2015 - Dawn Arrives in Third Mapping Orbit

Dawn completed the maneuvering to reach its third mapping orbit and stopped ion-thrusting this afternoon. This was a little ahead of schedule because the spiral descent went so well that some of the allocated thrusting time was not needed. Since July 14, the spacecraft has reduced its orbital altitude from 2,700 miles (4,400 kilometers) to approximately 915 miles (1,470 kilometers). The orbit period has correspondingly decreased from 3.1 days to 19 hours.

Dawn is scheduled to begin its new observations on the evening of Aug. 17 (PDT) and continue for more than two months. First, however, the mission control team will measure the actual orbit parameters accurately and transmit them to the spacecraft.

August 10, 2015 - Dawn Resumes Ion-Thrusting After a Day of Planned Coasting

Dawn is now below 1,050 miles (1,690 kilometers) in orbital altitude and using its ion engine to descend further.

Mission controllers formulate the flight plan for the spirals with extra maneuvering time in case it's needed to stay exactly on course. The descent has been going so well that they instructed the spacecraft to coast for almost 23 hours on Aug. 9 and 10. Observations in the next mapping phase cannot begin early for several technical reasons, including the complexity of advancing the carefully timed computer instructions already prepared and the schedule for the Deep Space Network. Therefore, mission planners are keeping the ship close to the originally planned trajectory rather than getting ahead.

August 7, 2015 - Dawn Continuing On Course and On Schedule

Dawn is continuing to use its ion engine to maneuver to a lower orbit. Today it is just above 1,100 miles (1,800 kilometers). It has now reduced its orbital period to about 24 hours. In its targeted mapping orbit at an altitude of 915 miles (1,470 kilometers), the spacecraft will circle Ceres every 19 hours.

August 3, 2015 - Dawn Completes More than Half of Descent

Dawn has completed more than half of the maneuvering to reach its next mapping orbit. The coils in its descent spiral are getting tighter and tighter as it goes. Over the course of the day today, the spacecraft reduces its orbital altitude from 1,300 miles (2,100 kilometers) to 1,250 miles (2,000 kilometers).

July 31, 2015 - Dawn Descent Proceeding Well

Dawn has lowered its altitude to 1,400 miles (2,300 kilometers). Closer to Ceres, where it feels the dwarf planet's stronger gravitational pull, the spacecraft must travel faster in its orbit. It is now circling Ceres at 340 mph (550 kilometers per hour). At this lower altitude and higher speed, Dawn's orbit period is 1.3 days.

Once a week during the descent from the second mapping orbit to the third, the probe pauses ion-thrusting and points its main antenna to Earth. Controllers transmit an updated flight plan during these communications sessions. (This process was explained here.) The communications session yesterday confirmed that Dawn remains healthy and is continuing to perform all of its tasks very well.

The July Dawn Journal includes an updated illustration of the spiral path Dawn is following and presents other details of the adventurer's recent and upcoming activities.

July 27, 2015 - Dawn Orbiting Closer to Ceres

Today the spacecraft is orbiting 1,600 miles (2,600 kilometers) above the ground. As with all of Dawn's complex maneuvers from each mapping orbit to the next, the spacecraft is not taking a perfect spiral path for technical reasons. The altitude does not change as much over the course of the day today as it does some other days. Nevertheless, the probe is accurately following its carefully designed course.

July 23, 2015 - Dawn Maneuvering to Lower Orbit

As Dawn maneuvers closer to Ceres, today it is reducing its altitude from 1,900 miles (3,100 kilometers) to 1,800 miles (2,900 kilometers).

In lower orbits, the spacecraft circles Ceres more quickly, not only because the distance around the orbit is shorter but also because it travels faster in the dwarf planet's tighter gravitational grip. (For more on this, see this Dawn Journal explanation.) In the previous mapping orbit (at 2,700 miles, or 4,400 kilometers), it took slightly more than three days to complete one revolution. Now the orbital period is a little less than two days. When Dawn is in its next mapping orbit (at 900 miles, or less than 1,500 kilometers), each loop will take about 19 hours.

July 22, 2015 - Dawn, Ceres and Earth Closest To Each Other

As Ceres (with its new permanent resident, Dawn) and Earth follow their own independent orbits around the sun, today they are at their closest since June 2014. The dwarf planet and Dawn today are 180 million miles (290 million kilometers) from our home. (For more details and a diagram, see the June Dawn Journal.)

Meanwhile, Dawn is continuing to thrust with its ion propulsion system to shrink its orbit. Today it will descend from 2,000 miles (3,200 kilometers) to 1,900 miles (3,100 kilometers).

July 20, 2015 - Dawn's Spiral Descent Continuing Smoothly

Dawn is continuing to lower its orbital altitude. Today the spacecraft will descend from 2,200 miles (3,500 kilometers) to 2,100 miles (3,400 kilometers).

In its previous mapping orbit, the explorer was 2,700 miles (4,400 kilometers) above the alien world. When it completes its spiral to the third orbit, it will be about 900 miles (less than 1,500 kilometers) high.

July 17, 2015 - Dawn Maneuvering to Third Science Orbit

NASA's Dawn spacecraft is using its ion propulsion system to descend to its third mapping orbit at Ceres, and all systems are operating well. The spiral maneuvering over the next five weeks will take the spacecraft to an altitude of about 900 miles (less than 1,500 kilometers) above the dwarf planet.

The spacecraft experienced a discrepancy in its expected orientation on June 30, triggering a safe mode. Engineers traced this anomaly to the mechanical gimbal system that swivels ion engine #3 to help control the spacecraft's orientation during ion-thrusting. Dawn has three ion engines and uses only one at a time.

Dawn's engineering team switched to ion engine #2, which is mounted on a different gimbal, and conducted tests with it from July 14 to 16. They have confirmed that the spacecraft is ready to continue with the exploration of Ceres.

By the end of the day on July 17, Dawn will have descended to an altitude of about 2,400 miles (3,900 kilometers). After arrival at its next mapping orbit -- called the High-Altitude Mapping Orbit, or HAMO -- in August, Dawn will begin taking images and other data at unprecedented resolution.

July 15, 2015 - Dawn Performing System Checkout in Ceres Orbit

As part of their investigation of the anomaly on June 30, engineers have performed some further configuration changes on the spacecraft, and they are now conducting a test to confirm that all systems are operating well and ready to continue with the exploration of dwarf planet Ceres.

July 13, 2015 - Dawn Healthy as it Orbits Ceres

Dawn remains healthy and functioning normally in its second mapping orbit at Ceres. Engineers are continuing their investigation into the anomaly that caused a discrepancy in the orientation on June 30.

July 6, 2015 - Dawn Holding in Second Mapping Orbit

NASA's Dawn spacecraft is healthy and stable, after experiencing an anomaly in the system that controls its orientation. It is still in its second mapping orbit 2,700 miles (4,400 kilometers) above dwarf planet Ceres.

On June 30, shortly after turning on its ion engine to begin the gradual spiral down to the next mapping orbit, its protective software detected the anomaly. Dawn responded as designed by stopping all activities (including thrusting), reconfiguring its systems to safe mode and transmitting a radio signal to request further instructions. On July 1 and 2, engineers made configuration changes needed to return the spacecraft to its normal operating mode. The spacecraft is out of safe mode, using the main antenna to communicate with Earth.

Dawn will remain at its current orbital altitude until the operations team has completed an analysis of what occurred and has updated the flight plan.

Because of the versatility of Dawn's ion propulsion system and the flexibility of the mission's plan for exploring Ceres, there is no special "window" for starting or completing the spiral to the third mapping orbit. The plans for the third and fourth mapping orbits can be shifted to new dates without significant changes in objectives or productivity.

June 30, 2015 - Dawn Successfully Completes Second Ceres Mapping Orbit

Dawn is over the nightside of Ceres and nearing the end of the eighth and final revolution in its survey orbit phase.

During the observations on June 27, the camera's internal computer reset and about three hours later the computer in the visible and infrared mapping spectrometer reset. The operations team observed both events in telemetry transmitted through one of the spacecraft's auxiliary antennas and concluded no prompt response was necessary. Dawn continued to perform all of its other functions smoothly. (More details are here.)

The second mapping orbit has now concluded successfully. See the June 29 Dawn Journal for a summary of the accomplishments in this mission phase at an altitude of 2,700 miles (4,400 kilometers).

Tonight Dawn will power on its ion propulsion system to begin a spiral descent to the third mapping orbit. It will take about five weeks to complete the maneuvering to an altitude of about 900 miles (less than 1,500 kilometers).

June 25, 2015 - Dawn Performing Penultimate Survey Orbit Observations

Early in the morning on June 24, the spacecraft began its seventh arc over the lit side of Ceres. It has been acquiring spectra and photographs since then. It will cross from the day side to the night side over the south pole later today and will begin transmitting its data shortly after that.

Dawn's final set of observations at this altitude will start on June 27.

June 22, 2015 - Mapping of Ceres Continuing Smoothly

On June 20, Dawn completed transmitting the results of its fifth set of observations. After 10:00 PM PDT that day, it traveled once again 2,700 miles (4,400 kilometers) over the terminator from the night side to the day side of Ceres. The probe is now collecting more pictures and spectra in infrared and visible. After its orbit takes it to the dark side later today, it will turn to point its main antenna to Earth to relay its latest results.

June 18, 2015 - Dawn Now in Second Half of Second Mapping Phase

Dawn is now on its fifth flight over the sunlit side of Ceres in this phase of the mission. It is operating well as it takes more pictures and spectral measurements. The explorer will continue its observations until tomorrow morning when it will pass over the south pole. Then when it flies once again over the unilluminated side, it will send the data to Earth.

During the fourth observing period on June 15, the visible and infrared mapping spectrometer’s internal computer detected an unexpected condition and stopped collecting data. The main spacecraft computer then powered the device off. The same events occurred in 2011 as Dawn was approaching Vesta. This time, as was the case four years ago, engineers and scientists concluded that the most likely cause was a cosmic ray strike. When it was powered back on for the fifth observing cycle, the spectrometer resumed normal operation.

Navigators are continuing to refine their measurements of Ceres’ gravity as they track Dawn’s orbital motion, and they are now using the results to design the next spiral maneuvers with the ion propulsion system. The spacecraft is scheduled to begin lowering its orbital altitude at the end of this month following the conclusion of its eighth revolution.

June 15, 2015 - Dawn Conducting Fourth Set of Survey Observations

On June 13 and 14 Dawn transmitted to distant Earth all of the data from its third dayside observations of Ceres. Yesterday the spacecraft began its fourth trip over the illuminated side of the dwarf planet at this altitude (2,700 miles, or 4,400 kilometers). As Dawn flies south, it will observe the alien world until looping back to the night side again tomorrow morning, when it will start transmitting the results to distant Earth.

June 12, 2015 - Dawn Performing More Ceres Measurements

Dawn is orbiting over the side of Ceres lit by the sun, and it is taking more photos and making other observations. It will travel to the night side again on Saturday and will then turn to point its main antenna to Earth to report its findings.

The veteran explorer remains healthy, and all systems are operating well.

June 10, 2015 - Dawn Completes a Second Round of Observations

Dawn acquired more pictures and other measurements of Ceres in its second arc over the dayside of the dwarf planet. It is now on the night side, sending its precious data to NASA’s Deep Space Network.

Dawn’s third dayside passage over Ceres at this altitude will start tomorrow afternoon and continue for a little more than a day and a half.

June 8, 2015 - Dawn Conducts First Observations in New Science Phase

Dawn photographed Ceres and measured its spectrum in infrared and visible wavelengths as it orbited over the illuminated side on June 5 and 6. All measurements were completed as planned. When its orbit took it to the night side again, the spacecraft pointed its main antenna to Earth and transmitted its findings.

Later this morning it will travel back to the day side and begin its second set of observations.

June 5, 2015 - Dawn Begins New Science Phase

As Dawn flew 2,700 miles (4,400 kilometers) over Ceres’ north pole this morning, the spacecraft passed from the night side to the day side of the dwarf planet. That marked the beginning of the new mapping phase, and Dawn began taking photos and making other measurements on schedule. Circling Ceres every 3.1 days, Dawn will make extensive scientific observations when it is over the sunlit side and will transmit its findings to Earth when it is over the side in darkness. The pictures will be three times as sharp as those from the first mapping orbit. This mapping phase is scheduled to continue for eight revolutions, providing plenty of opportunities to gather a wealth of data.

June 3, 2015 -Dawn Arrives in Second Mapping Orbit

Dawn completed the maneuvering to reach its second mapping orbit and stopped ion-thrusting on schedule this morning. Since May 9, the spacecraft has reduced its orbital altitude from 8,400 miles (13,600 kilometers) to 2,700 miles (4,400 kilometers). The orbit period has correspondingly decreased from 15.2 days to 3.1 days. Dawn is scheduled to begin its new observations on June 5, as explained in the most recent Dawn Journal. First, however, the mission control team will measure the actual orbit parameters accurately and transmit them to the spacecraft.

June 1, 2015 - Dawn Closing in on Second Mapping Orbit

Dawn spent the weekend maneuvering with its ion propulsion system and is now almost in its targeted mapping orbit. Last night it completed its final ascent in this complicated trajectory. Today it is descending from 3,000 miles (4,900 kilometers) to 2,800 miles (4,600 kilometers). It is scheduled to conclude thrusting on June 3 at an altitude of 2,700 miles (4,400 kilometers).

May 28, 2015 - Dawn Receiving Updated Flight Profile

Dawn remains in good health as it has been reshaping its orbit around Ceres. Today the spacecraft orbits from 3,100 miles (5,000 kilometers) up to 3,400 miles (5,500 kilometers) and then will start to descend again. Meanwhile, it paused ion-thrusting this afternoon to point its main antenna to Earth for a routine telecommunications session. Engineers have refined the flight profile based on analyses of the recent optical navigation pictures as well as measurements of the orbit from the radio signal and other data. Controllers are transmitting the new information to Dawn, and it will resume thrusting tomorrow.

Today's Dawn Journal includes a summary of the first mapping orbit, the maneuvering it does between mapping orbits, the second mapping orbit and a suggestion to look at this mission status update.

May 26, 2015 - Dawn Reaching to Lower Altitudes

Dawn is following the carefully plotted trajectory around Ceres, maneuvering to prepare for its second mapping campaign next month. The probe's mapping orbits are nearly circular, but during the flight from one to another, the intermediate orbits are more elliptical. Tonight Dawn's complicated route will take it temporarily below the targeted mapping orbital altitude of 2,700 miles (4,400 kilometers). It will descend to 2,500 miles (4,100 kilometers) tomorrow before beginning another ascent.

On May 22 Dawn photographed Ceres to help the navigation team maintain a tight fix on its orbital position. Controllers used the opportunity to acquire bonus visible and infrared spectra.

May 22, 2015 - Dawn's Orbital Maneuvers Progressing Well

Dawn has made good progress this week continuing to reshape its orbit around Ceres. Today the spacecraft's altitude reaches down to 3,100 miles (5,000 kilometers). Now, as earlier in the week, it will ascend slowly for a while, traveling up to 4,200 miles (6,700 kilometers) on May 24. Even as it climbs, Dawn will continue using its ion engine to maneuver to the next planned mapping orbit at 2,700 miles (4,400 kilometers).

Later today the explorer will stop ion-thrusting to take pictures of Ceres for navigation. This is the second and final photo op between mapping orbits. Dawn will resume thrusting tomorrow.

May 18, 2015 - Dawn’s Complex Maneuvering Continues Smoothly

On May 16, Dawn paused ion-thrusting to observe Ceres for two hours. Navigators use the pictures to help refine the trajectory as the spacecraft winds its way down to lower altitudes. The probe collected bonus infrared and visible spectra as well.

Dawn remains on course for its complex flight from the first mapping orbit to the second. Last week, the spacecraft descended every day. After dipping down to 4,400 miles (7,100 kilometers) on May 17 and 18, now the ship is slowly ascending as it continues to reshape its orbit around the dwarf planet. It will sail up to nearly 5,200 miles (more than 8,300 kilometers) tomorrow before descending again.

May 15, 2015 - Dawn Spiraling Lower

Dawn is using its ion engine to maneuver to its second mapping orbit, which will be 2,700 miles (4,400 kilometers) high. It will reach that altitude in early June.

During the course of the day today, Dawn’s altitude will decrease from 5,500 miles (8,900 kilometers) to 4,800 miles (7,700 kilometers).

Tomorrow the spacecraft will pause ion-thrusting to take pictures of Ceres for navigation.

May 11, 2015 - Dawn Spiraling to Lower Altitude

On May 9 Dawn began the spiral descent to its second mapping orbit. Today the spacecraft is at an altitude of about 8,000 miles (13,000 kilometers).

May 8, 2015 - Dawn Completes First Mapping Campaign

Yesterday Dawn successfully completed its final observations in this mapping orbit, focusing on Ceres' southern hemisphere. It is transmitting the pictures and other scientific data to Earth now.

It takes about 15 days to make one orbital revolution around Ceres at this altitude (8,400 miles, or 13,600 kilometers). Today the spacecraft completed one revolution since its arrival in this orbit on April 23. It is scheduled to start ion-thrusting tomorrow to spiral down to its second mapping orbit. (The orbital spirals were described in the April 2014 Dawn Journal.)

May 6, 2015 - Dawn Observes Ceres' Equatorial Region

The spacecraft is continuing to perform flawlessly in its first mapping orbit at Ceres. Last night Dawn completed its second set of dayside observations at this altitude. Earlier in the evening, the probe flew southward over the equator as it was taking pictures and making other measurements. It is now relaying its findings to Earth.

May 4, 2015 - Dawn Observes Ceres' Northern Hemisphere

Now orbiting over the side of Ceres illuminated by the sun, Dawn collected images and spectra of the northern hemisphere yesterday and today. It is sending its findings back to Earth today and tomorrow.

May 1, 2015 - Dawn Completes Night Side Measurements

Dawn concluded its observations from the night side of Ceres today. It is now transmitting to Earth the large volume of data it collected.

At this altitude, it takes just over 15 days to complete one revolution around Ceres. Dawn's leisurely orbit will bring it from the night side to the day side later today. The spacecraft is scheduled to observe Ceres again on May 3-4 while it flies over the northern hemisphere on the day side. For the complete schedule of observations in this first mapping orbit, see the March 31 Dawn Journal.

April 29, 2015 - Dawn Observing Ceres Again

Dawn is observing Ceres from the night side of the dwarf planet. On April 27 and 28, the spacecraft transmitted to Earth the data it had collected during its first science observations of the southern hemisphere. Its orbit is taking it north, and it passed over the equator on April 28. Although the ground directly beneath it is still in darkness, it is viewing the illuminated terrain of the northern hemisphere, much like a crescent moon.

April 27, 2015 - Update: Dawn Enters Science Orbit

Dawn began its science operations at 7:25 p.m. PDT/10:25 p.m. EDT on Friday, April 24 and performed as expected over the weekend.

April 24, 2015 - Dawn Enters Science Orbit

NASA's Dawn spacecraft entered into its first science orbit on Thursday, April 23, as scheduled. Following a delay in communicating a command sequence, the spacecraft briefly entered into safe mode and awaited further instructions, which were sent by mission controllers. As of early Friday, April 24, the spacecraft returned to normal operating mode and the mission team continues to prepare for science data collection

April 23, 2015 - Dawn Commences its First Science Oribt

Launched on September 27, 2007, the Dawn spacecraft is finally ready to embark on its prime science campaign at Ceres. On April 23rd, at around 1:00 AM PDT, Dawn completed the ion thrusting necessary to shape its first mapping orbit "RC3." Dawn is now in a circular, polar orbit about 8,400 miles (13,600 kilometers) in altitude with an orbit period of about two weeks.

The most recent Ceres pictures show the famous bright spots again (Ceres' Bright Spots Come Back Into View | NASA). These final images of the approach phase were taken from a vantage point 14,000 miles (22,000 kilometers) above the north pole as the spacecraft crossed the terminator from the dark side of the dwarf planet to the lit side.

Dawn maneuvered extensively with the ion propulsion system to reach this mapping orbit. Since entering orbit around Ceres on March 6, it has changed its velocity by 250 mph. The total velocity change accomplished since launch is 24,000 mph (nearly 39,000 kilometers per hour.) This is not the speed Dawn is traveling, however. See the February 2013 Dawn Journal for an explanation of the velocity change.)

March 31, 2015 - Dawn Closing in on Ceres

Dawn is in an elliptical orbit at an altitude of 40,000 miles (64,000 kilometers), traveling at 73 mph (117 kilometers per hour) relative to Ceres. The spacecraft passed the highest point of its elliptical orbit on March 18, where Ceres' gravitational pull was the weakest and Dawn's orbital velocity the lowest, and is closing back in on the dwarf planet, slowly picking up speed.

The spacecraft is still on the shadowed side of Ceres. It is continuing to use its ion propulsion system to reshape its orbit, targeting its first circular science orbit at an altitude of 8,400 miles (13,500 kilometers), which it is on schedule to achieve on April 23. For more information, read this month's Dawn Journal.

February 28, 2015 - Dawn Approaching the Dark Side of Ceres

Dawn is in the final stages of its approach trajectory to Ceres and will slip into orbit around the dwarf planet March 6, 2015. Dawn halted ion thrusting four times this month to take pictures of the dwarf planet for use in navigation. The spacecraft reached its closest distance to Ceres this past week. On Feb. 23 it was less than 39,000 kilometers (10% of the Earth-moon distance); Dawn will not be that close again until early April. This month's Dawn Journal and a new video: Destination Ceres: Breakfast at Dawn, explain Dawn's unique trajectory to Ceres and what we can anticipate when science orbits begin in April.

January 29, 2015 - Dawn Approaching Ceres and Seeing the Sights

Dawn devoted November to ion thrusting, and it is now about three times as far from Ceres as the moon is from Earth. As Earth and Dawn follow their separate orbits around the sun, they are moving to opposite sides of the solar system's star. To learn how to use the sun to locate Dawn early in December, see the November Dawn Journal, which also describes the new route the spacecraft will take into orbit around the dwarf planet.

December 29, 2014 - Dawn Begins Approach Phase to Ceres

Having accomplished another month of ion thrusting, and now more than two years after embarking on its journey away from protoplanet Vesta, Dawn is beginning its approach phase to dwarf planet Ceres. This month's Dawn Journal presents an overview of the mysterious world ahead.

Early in December, Dawn obtained its first resolved photo of Ceres, spanning nine pixels. Its next pictures will be taken on Jan. 13.

November 30, 2014 - Dawn Thrusting on Opposite Side of the Sun

Dawn devoted November to ion thrusting, and it is now about three times as far from Ceres as the moon is from Earth. As Earth and Dawn follow their separate orbits around the sun, they are moving to opposite sides of the solar system's star. To learn how to use the sun to locate Dawn early in December, see the November Dawn Journal, which also describes the new route the spacecraft will take into orbit around the dwarf planet.

October 31, 2014 - Dawn Continues Smoothly Toward Ceres

As the spacecraft continues ion thrusting to reshape its orbit around the sun to match Ceres' orbit, it is moving ever closer to the dwarf planet. At the end of this month, Dawn is about 1.3 million miles (2.1 million kilometers) from Ceres, closing in at less than 900 mph (0.4 kilometers per second). It is on course for arriving in orbit in early March 2015. A summary of the schedule for photographing Ceres during the approach phase in January and February is in the October Dawn Journal, and a more detailed description will be presented in November.

September 27, 2014 - Seven Years and Going Strong

On the seventh anniversary of its launch, Dawn's mission is continuing to go well. As it thrusts with its ion propulsion system, it is now less than 10 times farther from Ceres than Earth is from the moon.

Dawn has thrust for 68 percent of the time it has been in space (1,741 days), effectively changing its speed by 22,800 mph (10.2 kilometers per second). All this thrusting has consumed only 808 pounds (367 kilograms) of xenon propellant. For more details on the progress it has made in seven years of its deep-space adventure, see the latest Dawn Journal.

Earlier in the month, on Sep. 11, a high-energy particle of radiation struck an electrical component, causing the ion thrust to stop. The operations team guided the spacecraft back to normal operations, and ion thrusting resumed on Sep. 15. The October Dawn Journal will detail what occurred on the spacecraft, how the team dealt with it, and how the interruption in thrusting will change the approach phase of the Ceres mission. (The plan for scrutinizing Ceres from a series of progressively lower orbits will not change.)

August 31, 2014 - Another Month of Ion Thrusting Complete

The spacecraft has completed another month of ion thrusting, bringing it ever closer to its rendezvous with Ceres. Dawn is now 3.0 million miles (4.8 million kilometers) from Ceres and approaching it at less than 1500 mph (2400 kilometers per hour). Dawn's fourth and final phase of orbital observations will be at 230 miles (375 kilometers) above the dwarf planet's surface. The three month low altitude mapping orbit is previewed in the August Dawn Journal, along with a brief look at what might happen after the conclusion of the planned mission.

July 31, 2014 - Spacecraft Cruising Smoothly; Mission Control Simulates Problems

Dawn is propelling itself to Ceres with ion engine #1, which was not used from January 2010 until May 2014. Engineers verified that all the sensors the probe will use to explore Ceres are healthy. While the mission continues smoothly, the control team simulated dealing with a host of problems on the distant spacecraft. The July Dawn Journal provides an update on activities on the spacecraft and in mission control.

June 30, 2014 - Dawn's Deep Space Voyage Going Well

With another month of ion thrusting complete, Dawn's interplanetary journey to Ceres continues to go well. It will spend about two months at an altitude of 910 miles (1,40 kilometers) for the third orbital phase of its exploration of the alien world. For a preview, read the June Dawn Journal.

May 31, 2014 - Dawn's Journey Continuing Smoothly

The spacecraft devoted most of May to more gentle ion thrusting, bringing it ever closer to its rendezvous with dwarf planet Ceres. Dawn's second orbital phase around the dwarf planet will be at an altitude of 2,730 miles (4,400 kilometers). The May Dawn Journal presents a preview of this “survey orbit.”

April 30, 2014- Dawn Less than One Year from Ceres

Dawn is making good progress on its journey to Ceres and is now less than a year from arrival. To perform all of its planned observations, it will take advantage of the remarkable capability of its ion propulsion system by maneuvering extensively in orbit to provide different perspectives. The April Dawn Journal explains how the ship will spiral down to lower and lower altitudes above the alien landscapes.

March 31, 2014 - Dawn Nearing Earth as It Climbs to Ceres

As Dawn continues its ion thrusting to reach Ceres, the independent orbits the spacecraft and Earth follow are about to bring them to their closest point since 2011. They will never be this near each other again, although Dawn is still farther from Earth than the sun is. To learn more about this intriguing orbital choreography, visit the March Dawn Journal.

The Dawn flight team received the National Air & Space Museum 2014 Trophy for Current Achievement. The Smithsonian Air & Space Magazine has a story about it here, and the Smithsonian made this video.

February 28, 2014 - Dawn on Course and on Schedule as Ion Thrusting Continues

Dawn has completed another month of ion thrusting toward Ceres. After it is captured by Ceres's gravity early next year, it will continue descending to an altitude of 8,400 miles (13,500 kilometers) for its first intensive observations. Continuing the preview of the explorer's mission at the dwarf planet, the February Dawn Journal explains what the spacecraft will do during that orbit phase.

January 31, 2014 - Dawn Continues Spiraling to Ceres

Dawn continues its spiral outward from the sun, heading for Ceres. The spacecraft is gradually changing its orbit so that it matches Ceres's orbit around the sun. In a little more than a year, this will allow the probe to be captured by the dwarf planet's gravity. Thanks to its ion propulsion system, Dawn's gentle, graceful entry into orbit is very different from the tense, whiplash-inducing method used by conventional missions. To learn more, visit the latest Dawn Journal for the second in a series of previews of how the ship will accomplish its ambitious mission at the alien world of rock and ice.

December 31, 2013 - Dawn More than Halfway from Vesta to Ceres

Dawn resumed ion thrusting early this month and ends 2013 by continuing to thrust toward its 2015 rendezvous with the dwarf planet ahead. The spacecraft is now closer to Ceres than to Vesta. For the first in a series of previews of what the probe will do when it reaches the mysterious alien world, visit the latest Dawn Journal.

November 30, 2013 - Dawn Accomplishes Special Assignments While Coasting to Ceres

Dawn is in an unusual part of its interplanetary trajectory during which coasting is preferable to ion thrusting. Engineers took advantage of this period to operate in a new "hybrid" mode, in which the spacecraft uses its two healthy reaction wheels plus its hydrazine-powered jets to control its orientation in space. This successful test paves the way for using hybrid when Dawn is in its lowest orbits at Ceres, where the system may extend the limited supply of hydrazine. Mission controllers also confirmed the health of the sensors that will investigate Ceres. Visit the Dawn Journal for details on Dawn's latest activities and intriguing milestones the spacecraft will pass in December.

October 31, 2013 - Dawn Plans a Hiatus in Ion Thrusting

Dawn completed another month of ion thrusting and is making excellent progress to Ceres.

Although a great deal of thrusting is required to reach its destinations in the main asteroid belt, the flight plan requires Dawn to coast soon for four weeks. See the latest Dawn Journal for details.

September 27, 2013 - Dawn Completes Sixth Year of Flight

Dawn celebrated its sixth anniversary of spaceflight by continuing to thrust with its ion propulsion system on the long journey from Vesta to Ceres, just as it has most of the last year.

The probe has thrust for 1,410 days so far in the mission, or 64 percent of the time since launch. Its effective change in speed is more than 8.7 kilometers per second (19,500 miles per hour), well in excess of what any other spacecraft has achieved under its own power. Thanks to the efficiency of the ion propulsion system, all this thrusting has consumed only 318 kilograms (701 pounds) of xenon propellant.

To see more about the spacecraft's progress in six years of interplanetary flight, visit the latest Dawn Journal.

August 30, 2013 - Dawn and Earth on Opposite Sides of the Sun

As Dawn travels through the main asteroid belt independently of Earth's motion around the sun, the spacecraft and planet were on opposite sides of the solar system's star this month. Dawn was well in excess of one million times farther from Earth than the International Space Station. Visit the August Dawn Journal to read more about this extraordinary alignment.

June 30, 2013 - Dawn Sailing Smoothly With a Different Ion Engine

After relying on ion engine #3 since August 2011, engineers decided to command #2 to take over this month, and the ship is continuing to propel itself to dwarf planet Ceres. For more information on Dawn's three engines, and a comparison to a familiar ship from science fiction, see the June Dawn Journal.

May 31, 2013 - Dependable Dawn Continues Ion Thrusting

Dawn has completed its longest uninterrupted thrust period of the mission, more than 31 days. Thanks to the probe's dependability, controllers were able to devote time not only to preparing for Ceres but also to practicing how to recover from a spacecraft problem. Details are in the latest Dawn Journal.

April 30, 2013 - Dawn Closer to the Sun than Vesta as it Travels to Ceres

The spacecraft has accomplished another month of thrusting with its ion propulsion system, and it is making good progress to Ceres. In order to catch up with the dwarf planet, which is even farther from the sun than Vesta, Dawn temporarily has to go in closer to the sun than Vesta. The most recent Dawn Journal explains why.

March 29, 2013 - Mission Controllers Keep Dawn Flying to Ceres

With another month of ion thrusting complete, Dawn remains healthy. As it spends most of its time in powered flight, mission controllers spend most of theirs ensuring operations continue smoothly and preparing for Ceres. To learn more, see the latest Dawn Journal.

February 28, 2013 - Persistent Ion Thrusting Provides Tremendous Change in Velocity

Dawn has devoted another month to thrusting with its ion propulsion system as it heads for Ceres. The spacecraft has now changed its speed by more than 7.7 kilometers per second (17,000 mph) since it was launched, far more than any other spacecraft. That's about the same that it takes for a rocket to go into Earth orbit, but that is not what Dawn's thrusting has accomplished, and it is not the spacecraft's speed. For an explanation of this extraordinary velocity change, see the latest Dawn Journal.

January 31, 2013 - Dawn Continues Ion Thrusting to Ceres

Dawn has devoted the entire month of January to thrusting with its ion propulsion system to reach dwarf planet Ceres in 2015. Dawn has traveled far enough from Vesta that the protoplanet would appear to the spacecraft only as a bright pinpoint of light.

January 3, 2013 - Dawn Completes a Spectacular Year and Continues toward Ceres

Dawn ended its extraordinarily successful 2012 by smoothly continuing to thrust with its ion propulsion system to its 2015 rendezvous with dwarf planet Ceres. In December, as Earth and Dawn followed their independent orbits, they were at their closest distance in more than a year. As the spacecraft continues its interplanetary adventure, you can locate its position in the sky using the moon as a guide on Jan. 21. For more details, see the most recent Dawn Journal.

November 30, 2012 - Dawn's Operating Profile Modified to Conserve Hydrazine Propellant

Dawn's powered flight to Ceres is continuing smoothly. Mission controllers have changed its routine to conserve the hydrazine propellant it will use in its exploration of that dwarf planet. The spacecraft interrupts ion thrusting to turn to point its main antenna less frequently now. In addition, when it does turn, it moves more slowly. The most recent Dawn Journal describes these changes and the motivation for them.

November 2, 2012 - Dawn Continues Thrusting as it Begins Approaching the Sun

Dawn spent most of the past month continuing to reshape its orbit with its ion propulsion system. Although it is making good progress toward Ceres, which is farther from the sun, its course is now bringing it temporarily closer to the sun. It will not be this far from the sun again until May 2014. The latest Dawn Journal explains this enigmatic behavior.

Although most spacecraft coast most of the time, Dawn has now accumulated three years of ion thrust, and much more powered flight is ahead.

September 27, 2012 - Dawn Completes Fifth Year of Flight

Dawn celebrated its fifth anniversary of spaceflight by continuing to thrust with its ion propulsion system on the long journey from Vesta to Ceres, just as it has most of the time since leaving the protoplanet earlier this month.

The probe has thrust for 1,060 days so far in the mission, or 58 percent of the time since launch. Its effective change in speed is more than 7.1 kilometers per second (16,000 miles per hour), well in excess of what any other spacecraft has achieved under its own power. Thanks to the efficiency of the ion propulsion system, all this thrusting has consumed only 267 kilograms (587 pounds) of xenon propellant.

To see more about the spacecraft's progress in five years of interplanetary flight, see the latest Dawn Journal.

September 5, 2012 - Dawn Leaves Vesta Orbit

As Dawn thrust gently with its ion propulsion system, it escaped from orbit around Vesta last night, taking with it the stunning successes of its exploration of that alien world. Leaving orbit was as smooth and gradual as all other maneuvers in the mission, thank to the ion propulsion system. Dawn is now back in orbit around the sun and headed for dwarf planet Ceres. The latest Dawn Journal has details about Dawn's departure.

Dawn is about 19,000 kilometers (11,800 miles) from Vesta today, and the distance is constantly increasing.

Goodbye, Vesta!

August 28, 2012 - Dawn Takes a Parting Shot as it Ascends

Dawn's departure spiral has continued smoothly.

On August 25 - 26, at an altitude of 6,000 kilometers (3,700 miles), Dawn pointed its instruments at Vesta one last time for some final bonus observations. It took pictures and made other measurements of the northern hemisphere to see a little more terrain that has become illuminated since Dawn's previous observations in July. As Vesta's seasons progress, the equinox was on August 20, so the sun is now north of Vesta's equator for the first time since Dawn has been at Vesta.

August 20, 2012 - Dawn Continues Ascent

Dawn is continuing its gradual departure from Vesta. Today its average altitude is nearly 3000 kilometers (about 1850 miles). The last time it was this far from Vesta was August 1, 2011, near the beginning of its exploration of Vesta.

The September issue of Discover Magazine has an extensive article about Dawn's amazing mission at Vesta.

August 17, 2012 - Dawn Resumes Departure Spiral

Mission controllers returned Dawn to a standard operating configuration earlier this week after the reaction wheel developed increased friction. The spacecraft is now using its small hydrazine thrusters to control its orientation instead of the reaction wheels, just as it did from August 2010to May 2011.

Ion thrusting to follow the departure spiral will resume later today. Because of the hiatus in thrusting, escape will occur on September 5.

August 10, 2012 - Departure Delayed By Balky Reaction Wheel

Dawn interrupted its spiral ascent on August 8 when one of its reaction wheels, used for precise pointing, experienced increased friction. Another reaction wheel exhibited the same behavior in June 2010. As before, protective software turned the wheel off and used the small hydrazine jets to control the pointing. The spacecraft's orbital altitude is more than 2100 kilometers (1300 miles).

Controllers discovered the condition during a routine communications session on August 9. They are now replanning the departure and expect to resume ion thrusting at the end of next week. Escape from Vesta will be delayed by about 10 days, and then the spacecraft will be on its way to Ceres. (The flight from Vesta to Ceres was already planned to be performed with all the reaction wheels turned off.) To make up some of the time, most of the bonus departing observations will not be conducted.

August 8, 2012 - Dawn Continues Raising Orbital Altitude

Dawn is devoting most of its time to using its ion propulsion system to spiral away from Vesta after its extraordinarily productive exploration of the giant protoplanet. Today the spacecraft's average altitude is 1900 kilometers (1200 miles).

As explained in the most recent Dawn Journal, the probe is scheduled to observe Vesta several times during its departure..

July 25, 2012 - Dawn Completes Mapping Vesta and Begins its Departure

Dawn successfully completed its mapping of Vesta. The probe collected a rich set of pictures and other scientific data from this intensive phase of its exploration.

Now the spacecraft is using its ion propulsion system to gradually raise its orbit so it can escape from Vesta in late August and head for its appointment with dwarf planet Ceres in 2015. It will pause four more times to observe Vesta as it departs.

A summary of Dawn's accomplishments in this mapping orbit and plans for its final views of Vesta are in the July Dawn Journal.

July 19, 2012 - Dawn Concludes Topographical Mapping

Dawn completed the fifth cycle of mapping Vesta today. This was the last cycle to gather stereo images for the development of a topographical map of the newly illuminated regions of the northern hemisphere. The final cycle, like the first, will observe the terrain directly underneath the spacecraft. The visible and infrared mapping spectrometer continues to collect data in the same direction the camera is pointed.

July 14, 2012 - Dawn Acquires More Stereo Images

Dawn concluded the fourth of its six cycles of mapping Vesta. The spacecraft starts its fifth mapping cycle today, pointing the camera ahead and to the right of the point directly beneath it. It is continuing to gather visible and infrared spectra, as well.

July 9, 2012 - Dawn Continues Topographical Mapping

Dawn completed its third cycle of mapping Vesta while simultaneously collecting visible and infrared spectra. In the fourth mapping cycle, which begins today, the spacecraft will aim the sensors at the surface behind and to the right as it orbits. As described in the June Dawn Journal, the images will provide another new view for scientists to use in developing a topographical map of some regions of the previously unseen northern hemisphere.

July 4, 2012 - Dawn Completes First Stereo Mapping Cycle

Dawn has collected another complete set of images of the illuminated surface of Vesta. In this second of six planned mapping cycles, the spacecraft pointed the camera at an angle instead of straight down in order to acquire images for a topographical map. Today the probe began the third mapping cycle, now with the camera pointed both behind and a little to the left of the point directly beneath it. Dawn is continuing to acquire visible and infrared spectra as well. The strategy for mapping Vesta with new illumination is explained in the June Dawn Journal.

June 29, 2012 - Dawn Begins Stereo Imaging

Dawn successfully completed its first mapping cycle, and its second begins today. Instead of pointing the camera directly at the surface beneath it, the spacecraft is aiming it a little ahead and to the left. These images will provide a stereo view so scientists can develop a topographical map. In addition to the pictures, Dawn is using its visible and infrared mapping spectrometer to measure the nature of the minerals.

June 24, 2012 - Dawn Begins Photographing Vesta Again

Dawn has resumed taking pictures of Vesta. As in the mapping performed in October 2011, the first five-day cycle of mapping will be conducted looking straight down. In addition, the spacecraft is continuing to scrutinize Vesta with its visible and infrared mapping spectrometer. In each orbit, lasting just over 12 hours, Dawn aims its instruments at the surface when it is over the day side of Vesta, and it points its main antenna to Earth to transmit the data when it is over the night side.

June 15, 2012 - Dawn Begins New Observation Campaign

In its new orbit, known as the second high-altitude mapping orbit (HAMO2), Dawn began using its visible and infrared mapping spectrometer today to observe Vesta. The spacecraft is at an altitude of about 680 kilometers (420 miles), circling Vesta every 12 hours.

The operations team determined that spiral flight from the low-altitude mapping orbit to HAMO2 was executed so accurately that the fine tuning described in the June 5 mission status was not necessary.

June 5, 2012 - Dawn Nearly in Targeted Orbit

Dawn's complex spiral course from its low-altitude mapping orbit to its second high-altitude mapping orbit has been extremely smooth. It is now at the planned altitude of about 680 kilometers (420 miles). As described in the latest Dawn Journal, the spacecraft also needed to change the angle of its orbit plane from the sun, and that has been accomplished as well. Navigators now will make accurate measurements of the new orbit and then controllers will use the ion propulsion system to fine tune it to match exactly the conditions needed for the next intensive observation campaign, scheduled to begin on June 15.

May 29, 2012 - Dawn Progressing to Next Mapping Orbit

Dawn is making good progress to its next mapping orbit, thrusting with its ion propulsion system and sometimes using Vesta's gravity for a free ride. Today the craft's average altitude is about 590 kilometers (365 miles).

May 22, 2012 - Dawn's Climb to New Orbit Proceeding Well

Dawn continues to use its ion propulsion system to change its orbit around Vesta so it can conduct new observations. Today the spacecraft's average altitude is about 450 kilometers (280 miles).

May 15, 2012 - Dawn Continuing to Spiral Higher

Dawn's ascent to its next mapping orbit at an altitude of about 680 kilometers (420 miles) is progressing smoothly. As it uses its ion propulsion system to follow the complicated orbital route to the new target, today the probe's average altitude is about 355 kilometers (220 miles).

May 8, 2012 - Dawn Raising Orbital Altitude

The spacecraft is gradually raising its orbital altitude with its ion propulsion system, spiraling upward in a reverse of the method it used in November and December to reach the low altitude orbit. Dawn's altitude is constantly changing, but today the ship's average altitude is about 275 kilometers (170 miles).

May 1, 2012 - Dawn Concludes Outstandingly Successful Low Altitude Phase

Investigating Vesta since December 12 from an average altitude of 210 kilometers (130 miles), Dawn accumulated an extraordinary amount of information about this unique world. Now having exceeded all expectations for this phase of the mission, it began its six-week ascent to a higher orbit on May 1.

Dawn's orbital stay at Vesta is being extended by 40 days, and that allowed it to remain at low altitude for an extra month, performing even more observations. Additional time will be spent in higher orbits as well before it departs on August 26, 2012 for the long journey to Ceres.

The latest Dawn Journal summarizes the wonderful accomplishments in the low altitude orbit. In addition, new images continue to be posted every weekday at the Image of the Day.

March 29, 2012 - Dawn's Investigations of Vesta Continue

Dawn has had another very productive month of using all sensors to investigate Vesta. The spacecraft is operating very smoothly in its low-altitude mapping orbit.

Meanwhile, as Earth and Dawn follow their separate orbits around the sun, the probe is now on the opposite side of the sun from Earth. As explained in the most recent Dawn Journal, you can find the ship's approximate location by using the sun as a reference. Only a few probes have ever operated so far from home.

Go here to see new and intriguing views of the alien world Dawn is revealing.

February 29, 2012 - Dawn Continuing to Scrutinize Vesta from Low Altitude

Dawn has maintained its intensive pace of collecting data on Vesta. While priority remains on measuring the composition of the surface and mapping the gravity field, all scientific instruments are being used to study the protoplanet from an average distance of 210 kilometers (130 miles). The latest Dawn Journal describes the variations in altitude as Dawn loops around Vesta.

The plan for Dawn's year at Vesta had the spacecraft spending 70 days in the low altitude mapping orbit. As explained in the January and February Dawn Journals, operations at Vesta have gone so well that the 40 days held as margin to resolve problems are still available. Therefore, they are being applied to extend this phase of the exploration of Vesta. Dawn's measurements are now going beyond what had been anticipated.

On February 21, the spacecraft's main computer was temporarily overloaded with tasks, so it rebooted and the spacecraft entered safe mode. Operators responded quickly and had Dawn back to its normal operational configuration in less than three days.

A new image of Vesta is posted every weekday here.

January 27, 2012 - Low Altitude Mapping of Vesta Proceeding Well

Dawn is in good health and using all of its sensors to make detailed measurements of Vesta, following the pattern it has used from the beginning of the low altitude mapping campaign.

On January 13, a software bug caused the main computer to reboot and Dawn entered safe mode. The operations team soon detected the spacecraft's condition. They subsequently returned the probe to the correct configuration and resumed normal operations. Engineers understand how to avoid triggering this bug again.

December 29, 2011 - Dawn Observations in Low Altitude Orbit Continue Smoothly

Dawn spends most of its time measuring gamma rays and neutrons from Vesta so scientists can determine the abundances of elements in the material near the surface. The team is continuing to track the spacecraft in order to map Vesta's gravity field. Taking advantage of the low altitude, the imaging campaign continues to reveal new details of the surface.

The spacecraft performed another small adjustment to its orbit on December 24. These last two maneuvers were performed so accurately and the actual orbit is matching the predictions so well that the next two weekly adjustments have been canceled.

As the activities in the low altitude mapping orbit are intended to be highly repetitive, these mission status updates will be less frequent (thus saving your correspondent the effort of finding ways to restate what he wrote last week and this week). Updates will continue to be posted when events warrant and occasionally to reassure readers that the mission is continuing smoothly. More information about Dawn's work in this phase of the mission can be found in the Dawn Journals.

December 21, 2011 - Dawn Continues Gathering Science Data

Dawn is continuing to gather gamma ray spectra and neutron spectra in its low altitude orbit. In addition, scientists and engineers are making accurate measurements of the spacecraft's orbit to determine Vesta's gravity field.

The bonus imaging is yielding pictures more than three times better than those acquired in the high altitude mapping orbit.

Every week at this low altitude, Dawn will use its ion propulsion system to fine tune its orbit. (The reasons for this will be explained in an upcoming Dawn Journal.) The first of these weekly orbit adjustments was performed on December 17.

December 13, 2011 - Dawn Begins New Science Phase at Lowest Altitude

Dawn began a new set of science observations on schedule on Dec. 12 in its low altitude mapping orbit (LAMO) at an average altitude of 210 kilometers (130 miles). This phase will be the longest of the science campaigns at Vesta, lasting at least 10 weeks.

Dawn's investigations in this orbit will focus on measuring the elemental composition of the surface and subsurface material with the gamma ray and neutron detector and on mapping the interior structure by measuring Vesta's gravity field. In addition, the science camera and the visible and infrared mapping spectrometer will be used for some bonus observations. An overview of the plan for LAMO is in the Dawn Journal from Dec. 30, 2010, and further details will be in upcoming Dawn Journals.

The Dawn "image of the day" will take a break until Jan. 9. When it returns, there will be more spectacular views of this exotic world.

December 8, 2011 - Dawn Reaches Planned Orbit Altitude

Dawn has reached its target altitude, averaging 210 kilometers (130 miles) above Vesta.

On Dec. 3, while the spacecraft was turning in preparation for a final brief period of ion thrusting to refine its orbit, protective software detected a discrepancy in the orientation and put the spacecraft into safe mode. The discrepancy was a result of the spacecraft computing and then using a turn rate that was slightly too high. The operations team quickly established that the spacecraft was healthy, and on Dec. 5 they commanded it out of safe mode.

Mission planners already had several more windows planned for ion thrusting in order to make further fine adjustments to the orbit. Lengthening one of those windows allows sufficient time to compensate for the safe mode.

Science observations in the new orbit are scheduled to begin on Dec. 12.

December 1, 2011 - Dawn Continues Toward New Orbit

Dawn is getting close to its targeted altitude of 210 kilometers (135 miles). Today it is at an altitude of about 245 kilometers (145 miles). In addition to lowering its altitude, the spacecraft has changed the plane of its orbit most of the way to the new target as well, and it is now less than one degree from the intended value. (See the latest Dawn Journal for an explanation of the shift in the orbital plane.)

The spacecraft acquired more images of Vesta on Nov. 27.

Science observations in the new orbit are scheduled to begin on Dec. 12.

November 23, 2011 - Dawn Progressing to New Orbit

Dawn is continuing to make good progress toward its next planned orbit. The spacecraft thrusts occasionally with its ion propulsion system, but most of the time it coasts, letting Vesta's gravity reorient its orbit.

The spacecraft acquired some images of Vesta on November 20 and 23.

November 17, 2011 - Dawn Thrusting to a Lower Orbit

Dawn has been continuing to change its orbit with its ion propulsion system. Today the spacecraft reaches down to an altitude of about 265 kilometers (165 miles). While more ion thrusting lies ahead to reduce the altitude, the craft will spend most of the time before its next science phase begins on December 12 using Vesta's gravity to change the orientation of its orbit. (The target altitude and orientation and the method of achieving them will be explained in the next Dawn Journal.)

November 10, 2011 - Dawn Lowering Orbital Altitude

Dawn is using its ion propulsion system to lower its orbital altitude. Today the spacecraft is at an altitude of about 400 kilometers (250 miles).

On November 7 thrusting was halted for the spacecraft to collect some images of Vesta.

November 2, 2011 - Dawn Concludes Intensive Mapping

On October 31, Dawn completed the sixth and final mapping cycle. It spent another two days transmitting to Earth the last of the science data it had gathered. The successful completion of this mapping marks an extraordinary milestone in the exploration of Vesta. More information about this remarkable phase of the mission is in the October 31 Dawn Journal.

Today Dawn began thrusting with its ion propulsion system. It will take more than five weeks of maneuvering to reach the next science orbit.

October 26, 2011 - Dawn Concludes Topographical Mapping

Today Dawn successfully concluded its fifth mapping cycle and the final one devoted to topographical mapping. It is now beginning the last mapping cycle of the high altitude mapping orbit. This sixth cycle is nearly identical to the first and was included in the plan in case there were problems with the the first. As it was successful, most of these observations will provide views very similar to the ones already returned.

October 21, 2011 - Dawn Completes More Topographical Mapping

With its fourth mapping cycle complete, today Dawn began its fifth mapping cycle. This is the last one devoted to acquiring images for topography. The camera will mostly be pointed to the side as the spacecraft orbits Vesta.

October 16, 2011 - Dawn Reaches Halfway Point in HAMO Mapping

Dawn has completed its third mapping cycle in the high altitude mapping orbit (HAMO). Now it is beginning the fourth cycle, in which the spacecraft points its camera ahead at a different angle from the second cycle. The images from the different viewing angles will be combined to create topographic maps.

Observations with the visible and infrared mapping spectrometer and the gamma-ray and neutron spectrometer continue as well.

The mapping cycles are conducted in the order of their importance, so the most valuable measurements in HAMO have now been completed successfully.

October 11, 2011 - Dawn Gathers Images for Topographic Mapping

Dawn has completed its second mapping cycle. Instead of pointing the instruments straight down, as in the first cycle, the spacecraft aimed them at an angle, simultaneously ahead and to the side as it orbited Vesta. The third cycle will acquire images at a different angle, with the craft pointing both back and to the side. During this topographic mapping, spectra continue to be acquired with the visible and infrared mapping spectrometer.

Controllers working on the gamma-ray and neutron detector (GRaND) have eliminated the noise from the gamma-ray sensor. The instrument is healthy and operating normally.

October 5, 2011 - First Mapping Cycle Completed

Dawn's mapping of Vesta from an altitude of about 680 kilometers (420 miles) is going very smoothly. It has completed its first cycle of 10 orbits in which the principal objective was to acquire images looking straight down. Today the spacecraft will begin a new cycle of observing the surface at an angle to provide images scientists will use to create topographic maps and stereo images. This mapping strategy is described in more detail in the September 27, 2010 Dawn Journal.

Scientists and engineers are investigating increased noise in one of the gamma-ray sensors in the gamma-ray and neutron detector (GRaND).

September 29, 2011 - Dawn Begins New Science Campaign

Dawn began its new phase of Vesta observations today. Circling Vesta every 12.3 hours at an average altitude of 680 kilometers (420 miles), it will take pictures and acquire visible and infrared spectra when it passes over the day side and transmit the data to Earth while over the night side. This intensive phase of the mission will last about a month. Additional details on this high altitude mapping orbit are in the September 27, 2010 Dawn Journal.

The maneuvers to adjust the orbit earlier this week were executed very smoothly. In between them, on Sept. 27, Dawn celebrated its fourth anniversary of being in space. Additional anniversary details are in the Dawn Journal for September 27, 2011.

September 26, 2011 - Dawn Ready for Final Orbit Adjustment

Controllers have designed a pair of maneuvers with the ion propulsion system to adjust Dawn's orbit around Vesta to match it to the conditions needed for the planned observations in its new high altitude mapping orbit (HAMO). The first maneuver will be performed tonight and the second will be the next night.

The operations team has taken advantage of the period between the end of thrusting on Sept. 18 and the beginning of intensive science observations in HAMO to perform other activities. They have conducted bonus science measurements with all the instruments. In addition, they used the backup science camera to verify that it continues to be healthy. They have also performed further tests with the visible and infrared mapping spectrometer.

On Sept. 21, when the spacecraft was reconfiguring its memory in preparation for collecting science data in HAMO, a software function took longer than expected and caused the computer to reboot. As a result, Dawn entered safe mode. Controllers detected the condition that night, diagnosed the cause, and returned the spacecraft to its normal operating condition less than two days later.

September 20, 2011 - Dawn Nearly in New Science Orbit

On Sept. 18, Dawn successfully completed the majority of the planned ion thrusting needed to reach its new science orbit, the high altitude mapping orbit. Now navigators are measuring its orbital parameters precisely so they can design a final maneuver to ensure the spacecraft is in just the orbit needed to begin its intensive mapping observations next week. (An explanation of why the orbit needs adjustment can be found in the February 27, 2011 Dawn Journal.)

Dawn is orbiting at an altitude of about 680 kilometers (420 miles).

September 15, 2011 - Dawn Continues Spiraling to New Orbit

Dawn remains on course and on schedule as it uses its ion propulsion system to spiral to its next science orbit. The spacecraft begins the day today at an altitude of about 880 kilometers (550 miles) and ends it at 790 kilometers (490 miles).

September 8, 2011 - Dawn Lowering its Orbit

Dawn's spiral flight from survey orbit to its next science orbit is going very smoothly. As it continues to lower its altitude, the spacecraft begins the day today at about 1550 kilometers (960 miles) and ends it at 1330 kilometers (830 miles). For more on the unusual nature of Dawn's method of changing orbits, visit the February 27, 2011 Dawn Journal.

September 1, 2011 - Dawn Successfully Completes Survey Orbit Phase

Dawn completed survey orbit, returning more than 2,800 pictures covering the entire illuminated surface and over three million visible and infrared spectra, exceeding the objectives for this first scientific phase of the mission. The spectacular results will keep scientists busy (and happy!) for years. For more information on what Dawn accomplished in survey orbit, visit the September 1 Dawn Journal .

On August 31, the spacecraft resumed ion thrusting, and it will spend most of September spiraling down to the next science orbit, which is four times closer to Vesta than survey orbit.

August 24, 2011 - Dawn Completes Three More Day Side Passes in Survey Orbit

Dawn has now acquired images and spectra through a total of five passes over the lit side of Vesta, and the quality of the data remains excellent. The visible and infrared mapping spectrometer (VIR) experienced an anomaly on the third orbit very similar to the one on the first orbit, and engineers and scientists from the instrument team in Italy and the operations team at JPL are continuing to work to understand it.

The principal scientific objective of survey orbit is to acquire 5000 sets of spectra with VIR. VIR has already returned well in excess of 8000. All other objectives for survey orbit have also been met, so this phase of the mission is set to conclude on schedule on August 31.

August 16, 2011 - Dawn Completes Two Day Side Passes in Survey Orbit

Dawn has observed Vesta during two passes over its illuminated face, each lasting about 34 hours. It acquired all the images planned with the camera. After the visible and infrared mapping spectrometer (VIR) had successfully completed about 40% of its observations during the first orbit, its internal computer detected a temporary problem, so the rest were not performed. As explained in the latest Dawn Journal, plans included collecting more data than needed, so missing the observations is easily tolerated. During the subsequent communications session (while Dawn was over the night side), controllers verified the instrument was healthy and reconfigured it. VIR acquired all of the planned measurements during the second orbit. Scientists have confirmed that the data are of very high quality.

August 11, 2011 - Dawn Begins Survey Orbit Phase

Having successfully completed its approach phase, Dawn began its survey orbit observations today. (See the August 11, 2011 Dawn Journal for more on this. This is the first major science phase of the mission. During seven revolutions of 69 hours each, it will acquire images and spectra when it passes over the day side of Vesta and radio the results back to Earth over the night side.

During survey orbit, a new image will be posted here every day.

Dawn is in a circular polar orbit about 2700 kilometers (1700 miles) from Vesta.

August 7, 2011 - Dawn Completes Final Observations of Approach Phase

On August 6, Dawn acquired the last of its images and spectra in the approach phase. Meanwhile, mission controllers are completing the adjustments to the command sequences to be used for survey orbit observations beginning on August 11 when the spacecraft passes from the night side of Vesta to the day side. For an overview of survey orbit plans, see the Dawn Journal from May 27, 2010.

Dawn is in a circular polar orbit about 2700 kilometers (1700 miles) from Vesta.

August 2, 2011 - Dawn Completes Spiraling to Survey Orbit

Today Dawn completed the ion thrusting needed to reach its first science orbit. Now the operations team will refine measurements of its orbit and use that information to make final adjustments to the timing and other details of the commands the spacecraft will follow when it begins survey orbit observations on August 11.

On July 31, it paused thrusting to collect more images of Vesta.

Dawn is about 2700 kilometers (1700 miles) from Vesta.

July 26, 2011 - Dawn Acquires Images and Spectra During Coast Period

Dawn stopped ion thrusting on July 22 at an altitude of about 5200 kilometers (3200 miles) to begin its most intensive observations of the entire approach phase. Over the subsequent three days, the camera and the visible and infrared mapping spectrometer observed Vesta from northern latitudes to the south pole. Spectacular results will be unveiled on August 1.

Thrusting to spiral down to survey orbit is scheduled to resume on July 28.

July 21, 2011 - Dawn Flying Over Dark Side of Vesta

During its arc over the night side of Vesta, Dawn passed over the equator on July 20, still thrusting with its ion propulsion system. The angle of its orbit prevents the spacecraft from entering the shadow of Vesta.

During a communications session on July 20, engineers powered on the control unit that stopped operating valves on June 27. It had been off since then, with a different unit controlling the flow of xenon to the ion thruster. As they anticipated, the unit is now perfectly healthy, and it flawlessly completed all the tests they gave it. All evidence points to its temporary inability to control the valves as having been a result of a high energy particle of space radiation striking it. By turning it off and on again, the glitch was cleared. See the July 18, 2011 Dawn Journal for more details.

Dawn is about 6000 kilometers (3700 miles) from Vesta today and approaching it at 10 meters per second (22 mph).

July 19, 2011 - Dawn Spiraling Around Vesta

Even as it orbits around Vesta, Dawn is continuing to thrust with its ion propulsion system just as it did during its years of interplanetary cruise around the sun. The spacecraft is gradually spiraling down toward its survey orbit. As it began arcing over the south pole and heading toward the dark side of Vesta, Dawn acquired another set of images on July 18.

Dawn is about 9000 kilometers (6200 miles) from Vesta today and approaching it at 19 meters per second (43 mph).

July 17, 2011 - Dawn in Orbit Around Vesta

As Dawn continued thrusting, it was gently captured in orbit by Vesta around 10:00 PM PDT on July 15. Navigational analysis will be required to determine the exact time of capture. On July 16 it observed Vesta again.

Dawn is about 13,000 kilometers (8,000 miles) from Vesta today and approaching it at 23 meters per second (51 mph).

July 13, 2011 - Approach Phase Continues Smoothly

Dawn remains on course as it continues ion thrusting to reach its first science orbit in August. On July 12 it collected another set of Vesta images for navigation.

Dawn is about 23,000 kilometers (14,000 miles) from Vesta today and approaching it at 37 meters per second (83 mph).

July 10, 2011 - Dawn Completes Second Full Vesta Rotation Observation

After thrusting all week with its ion propulsion system, on July 9-10 Dawn acquired more images of Vesta. For the second time, it observed Vesta during one complete rotation of 5 hours, 20 minutes. The camera also acquired images of the space around Vesta to allow scientists to search for moons of the protoplanet.

Dawn is about 35,000 kilometers (22,000 miles) from Vesta today and approaching it at 50 meters per second (110 mph).

July 4, 2011 - Dawn Continues Closing in on Vesta

During a routine communications session on July 3, engineers verified that Dawn resumed thrusting, as instructed, on June 30. The spacecraft's approach phase is continuing, as the spacecraft spends most of the time thrusting with its ion propulsion system to bring its orbit closer to that of Vesta. It successfully acquired another set of navigation images on July 3.

Dawn is 65,000 kilometers (40,000 miles) from Vesta today and approaching it at 75 meters per second (170 mph).

July 1, 2011 - Dawn Completes First Full Vesta Rotation Observation

On June 29-30, Dawn observed Vesta throughout one full rotation of the protoplanet on its axis, which takes 5 hours 20 minutes. Both the camera and the visible and infrared mapping spectrometer (VIR) were used. After VIR had successfully completed some of its observations, its internal computer detected a temporary problem with the sensor, so the rest of its observations were not executed. Mission controllers subsequently verified that VIR is otherwise healthy.

On June 27, an electrical circuit that controls valves in the system that feeds xenon propellant to the ion thruster stopped operating. Software detected the anomaly, halted the thrust, and canceled other planned activities to point the main antenna to Earth. Engineers discovered it during a routine communications session on June 28. After assessing the state of the spacecraft, they sent instructions to switch to a different valve control circuit and resume thrusting on June 30 following the receipt of the data from the Vesta observations. The change in the thrust schedule does not affect the plan for the intensive Vesta science observation phase, which begins in August.

Dawn is 85,000 kilometers (53,000 miles) from Vesta today and approaching it at 90 meters per second (200 mph).

June 24, 2011 - Approach Phase Half Complete

Now more than halfway through the approach phase, Dawn completed another week of ion thrusting. It stopped thrusting twice this week to collect images for navigation.

Dawn is 145,000 kilometers (90,000 miles) from Vesta today and approaching it at 110 meters per second (250 mph).

June 17, 2011 - Dawn Increases Frequency of Vesta Observations

While still devoting most of its time in the approach phase to ion thrusting, Dawn now is observing Vesta more often. It halted thrusting on June 14 for navigation images and more test observations with the visible and infrared mapping spectrometer to prepare for later science observations. Today, it acquired another set of navigation images with the camera.

Dawn is 225,000 kilometers (140,000 miles) from Vesta today and approaching it at 140 meters per second (310 mph)..

June 8, 2011 - Camera and Spectrometer Observe Vesta Again

Continuing its weekly pattern, Dawn used its camera to image Vesta again today. In addition, the visible and infrared mapping spectrometer observed Vesta to help scientists choose proper instrument settings for when Dawn is close enough to begin its scientific measurements.

On June 6, Dawn's distance to Vesta was the same as Earth's distance to the moon. With the gradual nature of the approach inherent in the use of ion propulsion, the distance will continue to decrease slowly.

Dawn is 350,000 kilometers (220,000 miles) from Vesta today and approaching it at 190 meters per second (420 mph).

June 1, 2011 - Dawn Continues Smoothly in Approach Phase

Dawn continues to devote most of its time to thrusting with its ion propulsion system. Today it conducted its fifth session of acquiring images of Vesta for use in navigation.

Dawn is 470,000 kilometers (290,000 miles) from Vesta today and approaching it at 220 meters per second (490 mph).

May 24, 2011 - Dawn Observes Vesta for the Fourth Time

Dawn imaged Vesta again today, providing more data for navigators to use in refining the approach trajectory. As in interplanetary cruise, the majority of the week is devoted to ion thrusting.

Dawn is 640,000 kilometers (400,000 miles) from Vesta today and approaching it at 260 meters per second (580 mph).

May 17, 2011 - Dawn Completes More Vesta Navigation Observations

Dawn acquired another set of images of Vesta today. Navigators use the pictures of Vesta and the background stars to refine their determination of the spacecraft's trajectory. The results will be incorporated into updates to the plan for thrusting with the ion propulsion system. Meanwhile, the spacecraft is continuing to make good progress, spending most of its time thrusting.

Dawn is 810,000 kilometers (500,000 miles) from Vesta today and approaching it at 300 meters per second (670 mph).

May 10, 2011 - Dawn Observes Vesta with Camera and Spectrometer

The approach phase is going smoothly. Dawn stopped thrusting today for its second opportunity to acquire images of Vesta for use in navigation. In addition, the visible and infrared mapping spectrometer observed Vesta for the first time. The results will be used to set instrument parameters for subsequent measurements when the spacecraft is closer to its target.

Dawn is one million kilometers (620,000 miles) from Vesta today and approaching it at 340 meters per second (760 mph).

May 3, 2011 - Dawn Begins Vesta Mission Phase

Today Dawn concluded its interplanetary cruise phase and started the Vesta mission phase. The beginning of the approach phase is marked by the spacecraft's first pictures of Vesta. While Vesta appears very small at this distance (3.2 times the average distance between the Earth and moon), measuring its location against the background stars will help navigators pin down the position of Dawn relative to Vesta. Navigation images will be taken weekly until the middle of June, when the rate will increase.

The gamma-ray and neutron detector (GRaND) was powered on today, and it will remain on until Dawn departs Vesta in July 2012.

Other reconfigurations were made on the spacecraft as well, including turning the reaction wheels on.

During the approach phase, Dawn will continue to thrust most of the time with its ion propulsion system. It will enter orbit on July 16 and continue thrusting as it spirals to its first science orbit. The phase will end in the second week of August when survey orbit begins.

April 30, 2011 - Dawn Receives New Software

As usual, Dawn thrust for most of the month, bringing its orbit around the sun still closer to Vesta's orbit. April 11 to 19 was planned as a coast period so controllers could load a new version of software to the spacecraft's main computer. The new software would allow the spacecraft to operate with only two reaction wheels in the event one of the three healthy wheels becomes inoperable. This was the fourth time the software has been upgraded in flight, and the entire procedure was executed flawlessly. The complex work was completed in only three days.

Dawn is now only 3.4 times farther from Vesta than the moon is from Earth. The spacecraft is approaching Vesta at less than 0.39 kilometers per second (870 mph).

March 31, 2011 - Dawn Conducts Final Checkouts Before Vesta

Dawn spent most of the month thrusting toward its Vesta rendezvous but stopped for the week of March 14 in order to perform several final tests. All of the science instruments were powered on and checked out, and each one proved to be in excellent condition. In addition, controllers updated the software in the two identical science cameras. One of the gamma-ray sensors was carefully heated for five days to restore its sensitivity after years of exposure to radiation in space.

To refine their measurements of the thrust from the ion propulsion system, engineers commanded Dawn to align a thruster with Earth. They stepped the thruster through 13 of the throttle levels the spacecraft will use at Vesta while measuring the Doppler shift of the spacecraft's radio signal. These measurements show the change in the radio frequency caused by the change in the spacecraft's velocity, thus revealing the thrust. This procedure was performed with two of the thrusters to allow navigators to develop accurate flight profiles for maneuvering from one science orbit at Vesta to another.

February 28, 2011 - Dawn Successfully Completes Another Test for Vesta

Mission controllers conducted another test of the spacecraft's capability to operate in orbit around the giant asteroid. It executed some portions of the maneuvers it will perform in order to thrust along a spiral path from its high altitude mapping orbit to its low altitude mapping orbit. The probe's performance was very good and provided a valuable verification of its capabilities as engineers continue to prepare for Vesta operations.

January 31, 2011 - Spacecraft and Operations Team Practice for Vesta

In addition to thrusting most of this month, the spacecraft executed a rehearsal of one of the activities it will need to perform in its low altitude mapping orbit at Vesta. The test successfully demonstrated that even during the times that Vesta blocks the starlight used by a sensor to help orient the ship in the zero-gravity of spaceflight, an alternate kind of sensor can be used.

The operations team spent a week handling simulated problems during the approach phase to Vesta. The exercise included a wide variety of creative complications, including hypothesized damage to the spacecraft, unexpected characteristics of Vesta, loss of some planned Deep Space Network coverage, and unavailability of two members of the team. This "operational readiness test" is an important component of preparing for real operations.

After more than 2.2 years of powered flight, Dawn has now expended more than half of its original supply of 425 kilograms (937 pounds) of xenon propellant for its ion propulsion system. That has been enough to change the velocity by about 5.7 kilometers per second (nearly 13,000 mph), far more than any other spacecraft's propulsion system has achieved.

December 31, 2010 - Dawn Swaps Ion Thrusters

As it has each month this year, Dawn thrust for most of December, continuing to make excellent progress to Vesta.

Earlier this month, after using ion thruster #2 since January, mission controllers commanded the spacecraft to use thruster #3. After not being operated in two and a half years, #3 resumed thrusting smoothly and efficiently. All thrusters remain healthy.

Meanwhile, the operations team has been working on the sequences to be used in the third science phase at Vesta, known as the low altitude mapping orbit (LAMO). Dawn will spend two months in LAMO at an altitude of about 180 kilometers (110 miles).

November 30, 2010 - Upgrades Allow Reduced Hydrazine Consumption

Dawn devoted most of the month to continuing to thrust with its ion propulsion system.

Mission controllers radioed new parameters to the spacecraft to allow it to use less of its hydrazine propellant. Hydrazine is fired through the small reaction control jets to help the spacecraft hold stable or rotate in the zero-gravity of spaceflight. Even before powering off the reaction wheels in August, at which point the reaction control system took over, engineers began working on methods to use the hydrazine more efficiently. The successful operation with the new parameters this month was the culmination of that work.

October 31, 2010 - Dawn Thrusting to Vesta on the Far Side of the Sun

Dawn devoted most of October to thrusting on its interplanetary trajectory to Vesta. The spacecraft is on the opposite side of the sun from Earth and will reach its maximum distance from our planet on November 13.

September 28, 2010 - Dawn Completes Third Year of Flight

Dawn passed its third anniversary of being in space on September 27. It spent most of the month continuing to thrust with its ion propulsion system.

It has expended about 189 kilograms (417 pounds) of xenon in its 715 days of thrusting since launch. The effective change in speed so far is more than 5.0 kilometers per second (11,000 miles per hour). The Dawn team is developing the sequences the spacecraft will follow in its second Vesta science orbit, known as the high altitude mapping orbit (HAMO).

It will take about a month to spiral down from survey orbit to HAMO at an altitude of about 660 kilometers (410 miles). Dawn will spend a month in HAMO making more detailed observations of the surface.

August 31, 2010 - Dawn Motors Onward To Vesta

The spacecraft spent most of the month thrusting with its ion propulsion system. It is now so far from the Sun that the electrical power from the solar arrays is limited. The engineering team has implemented several of the power conservation measures that it had planned well in advance, including operating the ion propulsion system at a reduced throttle level.

The team also powered off the reaction wheels, switching control of the spacecraft's orientation to the reaction control system.

July 30, 2010 - Spacecraft and Its Instruments Continue to Operate Well

The spacecraft has now accomplished so much thrusting that it has accelerated by more than 10,000 mph over the course of the mission. As it continues to recede from the sun, it has passed 2.0 astronomical units, or twice Earth's average distance from the sun.

The week of July 19 was designated for coasting. Mission controllers used this time to operate each of the science instruments and proved all of them are in excellent health. A minor bug was corrected in the software in the cameras. Engineers also stored two copies of the new version of the software for the spacecraft's main computer in the spacecraft's backup computer.

The operations team successfully tested the procedures they will use for refining sequences of commands when Dawn is completing its approach to the first science orbit around Vesta in August 2011.

June 30, 2010 - New Software Installed in Main Computer

Dawn spent most of the month continuing to thrust to Vesta. On June 5, it surpassed the record set by Deep Space 1 (the first interplanetary ion propulsion mission) for the greatest velocity change by a spacecraft¹s propulsion system. It has now exceeded 4.4 kilometers per second (9,800 mph).

A coasting period from June 15 to June 24 was planned to allow the operations team to install new software in the spacecraft's main computer. They used the same procedure followed the last time (in April 2009), and it went smoothly. This latest version of software principally contains enhancements to aid in the acquisition of science data at Vesta and Ceres.

On June 17, spacecraft software detected an increase in the friction in one of the reaction wheels used for controlling the orientation. The spacecraft responded correctly by turning it off. Dawn normally uses only three of its four wheels, so it is continuing with that wheel powered off.

May 30, 2010 - Operations Team Continues Development of Survey Orbit Sequences

The Dawn team continued developing the sequences the spacecraft will use in survey orbit. That 17-day phase of the mission will allow extensive mapping with the science camera and the visible and infrared mapping spectrometer.

Meanwhile, the spacecraft completed another month of ion thrusting, remaining on course and schedule for its rendezvous with Vesta.

April 30, 2010 - Engineers Conclude Approach Phase Commands and Begin Survey Orbit

The development of approach phase commands concluded. They will be updated and refined next year before being radioed to the spacecraft. The team is now working on the commands that will be used in the first science orbit, which will be in August 2011. At an altitude of about 2700 kilometers (1700 miles), this will be the beginning of the intensive scientific observations of Vesta.

The spacecraft devoted most of the month to thrusting, and it continues to be in good health. An improved version of the December measurement of the relative alignment of the visible and infrared mapping spectrometer and the science camera was executed successfully.

March 31, 2010 - Engineers Continue Developing Approach Phase Commands

The team began running some of the commands the spacecraft will follow during the approach phase through the Dawn spacecraft simulator at JPL. Meanwhile, Dawn thrust with its ion propulsion system for most of the month, remaining on target for Vesta. The spacecraft is now farther from Earth than the Sun ever is, and it will never come as close as the Sun again.

February 28, 2010 - Dawn Now Farther than the Sun as It Continues to Vesta

Dawn made steady progress toward Vesta as it thrust for most of February.

This month, Dawn controllers began formulating the specific instructions the spacecraft will use for operating at Vesta. They are beginning with the "approach phase," which commences in May 2011 and concludes in August 2011, when Dawn has thrust to the first science orbit from which it will conduct intensive science observations. By the time Dawn actually begins the approach phase, most of the instructions for its year at Vesta will have been prepared.

Hubble Space Telescope observed Vesta on February 25 and 28 to collect data that will help refine plans for Dawn's mission.

On February 28, the spacecraft was as far from Earth as the Sun is, and it will never again be this close to the planet from which it began its mission.

January 31, 2010 - Dawn Swaps Ion Thrusters and Begins Receding from Earth

Dawn continued thrusting with its ion propulsion system for most of January, but mission controllers instructed it to stop using thruster #1 and start using thruster #2. All three thrusters are in excellent condition. This change is part of the plan to balance the use of the thrusters during the mission.

On January 18, Dawn and Earth reached their smallest separation since March 2008, although still more than 74 million miles from each other. Now, their separate orbits are taking them farther apart again.

December 31, 2009 - Dawn Continues Thrusting and Completes Engineering Tests

Dawn thrust with its ion propulsion system for most of December and remains On course for Vesta. the spacecraft conducted a set of special activities during the week of November 30. The gamma-ray and neutron detector (GRaND), visible and infrared mapping spectrometer (VIR), and science camera all were operated and verified to be healthy. “A measurement of the relative alignment of VIR and the science camera did not yield the desired data because of a conflict between commands within VIR, but the instrument remained healthy. The VIR commands are easily corrected, and the calibration will be executed early in 2010. Upgraded software was installed in the primary and backup cameras. Other spacecraft engineering activities were completed successfully as well.

November 30, 2009 - Dawn Completes Another Month of Interplanetary Thrusting

Dawn thrust with its ion propulsion system for most of November, pausing for less than half a day each week to point its main antenna to Earth.

The mission control team completed preparations for some special activities the spacecraft will execute in December (so check back next month to learn more!).

October 31, 2009 - Nearly in the Main Asteroid Belt, Dawn Continues Thrusting to Vesta

Dawn devoted most of the month continuing to thrust with its ion propulsion system. The spacecraft is healthy and making steady progress reshaping its orbit to rendezvous with Vesta. As it continues to climb away from the Sun, Dawn will reenter the main asteroid belt on November 13.

September 30, 2009 - Dawn Completes Second Year of Flight

Dawn passed its second anniversary of being in space on September 27. It spent most of the month continuing to thrust with its ion propulsion system. It has expended about 104 kilograms (230 pounds) of xenon in its 392 days of thrusting since launch. The effective change in speed so far is more than 2.6 kilometers per second (5800 miles per hour), far more than most spacecraft ever achieve with their propulsion systems.

August 31, 2009 - Dawn Maintains Steady Thrust to Vesta

Dawn devoted most of August to ion thrusting, as it will for most of the next two years leading to the rendezvous with Vesta. Controllers conducted routine maintenance on an ion thruster gimbal, reaction wheels, and gyroscopes this month.

August 3, 2009 - Dawn Spacecraft is Thrusting Nominally with the Ion Propulsion System (IPS)

The first Vesta scenario test executed successfully in the testbed last week, and the flight team reviewed the results. This test of a flight-like Vesta orbit sequence is an important step forward towards validation of the design and operations processes that will be used at Vesta.

July 30, 2009 - Dawn Continues Thrusting to Vesta

Dawn spent the month thrusting with its ion propulsion system. No special activities were conducted, allowing the spacecraft to devote as much time as possible to thrusting and permitting the operations team to engage in long-range planning for Vesta.

June 30, 2009 - Dawn Resumes Extended Thrusting

Dawn resumed its routine of long-duration thrusting with its ion propulsion system on June 8. The spacecraft is now following the same pattern it used for most of 2008, with only a single weekly interruption in thrusting to point the main antenna to Earth. Dawn had spent most of the time since October 31, 2008 coasting. In contrast, most of the time from now until arrival at Vesta will be devoted to thrusting.

May 25, 2009 - More Coasting Activities Completed

To verify that the software loaded in April could accomplish ion thrusting, the spacecraft executed two short thrust tests. Upon establishing that the software was performing well, engineers installed two copies in the backup computer and another copy in the backup location of the primary computer. Also this month, the xenon in part of the system to feed the propellant from the main tank to the thrusters was vented to space to allow mission controllers to calibrate pressure sensors.

April 30, 2009 - New Software Loaded to Main Spacecraft Computer

Mission controllers upgraded the software in the spacecraft's main computer this month. This was the first complete software replacement since November 2007. Running the new software required rebooting the computer, which puts Dawn into safe mode. The process of preparing the spacecraft, transmitting the software, rebooting, and recovering from safe mode all went extremely smoothly. Although the software was tested extensively before being radioed to the spacecraft, a short test of ion thrusting proved that no bugs were introduced that might interfere with this crucial capability.

On April 16, Dawn was at its closest distance to the Sun since last year. Now its elliptical orbit will carry it deeper into the solar system.

March 30, 2009 - Dawn Continues in Quiet Cruise

Dawn coasted quietly in its new orbit around the Sun this month. Controllers conducted some routine maintenance but devoted most of March to preparing for future special activities.

February 28, 2009 - Dawn Receives Gravity Assist from Mars

Dawn flew by Mars on February 17, successfully achieving the gravity assist it needed to help it reach the asteroid belt. The spacecraft passed less than 550 kilometers (340 miles) from the surface of the planet.

As Dawn was leaving Mars, fault detection software put the spacecraft into safe mode and canceled the bonus instrument calibrations. The cause was determined to be an inappropriate software response to an expected temporary loss of valid data from the spacecraft's star tracker in the vicinity of Mars.

The operations team subsequently commanded the spacecraft back to its normal configuration. In addition, they returned the bonus calibration data that had been transferred from the instruments to the main spacecraft computer prior to going to safe mode.

January 31, 2009 - Dawn on Course for Mars Gravity Assist

Engineers determined early this month that Dawn's trajectory to Mars is so good that the planned maneuver to fine tune it was not necessary. When Dawn flies by Mars on February 17, the planet's gravity will give the spacecraft a boost, helping it reach its targets in the asteroid belt.

The spacecraft has spent the month coasting with few activities occurring onboard. On January 20, the Gamma Ray and Neutron Detector was powered on so the instrument team could assess its health. The data it returned confirmed the unit is in good condition and operating normally.

December 31, 2008 - Dawn Passes Through Solar Conjunction

Dawn was on the opposite side of the Sun from Earth this month in an arrangement known as solar conjunction. The smallest separation between the Sun and the spacecraft was on December 12, when they were only about 1/3 degree apart as viewed from Earth. (To put this in perspective, the Sun itself appears to be 1/2 degree in diameter.) Communications were limited from December 5 to December 18, as the radio waves passing near the Sun experienced interference.

Although Dawn could have carried out more complex assignments even with the limited communications, no special tasks were necessary. The spacecraft continues to coast toward its February 17 gravitational assist from Mars.

Engineers have been gathering additional navigational data to use in fine tuning Dawn's trajectory in January.

November 30, 2008 - Dawn on Course for Mars Gravity Assist

Dawn needed to thrust with its ion propulsion system for less than 2.5 hours in November. The maneuver on November 20 was designed to adjust the trajectory to put it on course for a gravity assist from Mars on February 17, 2009.

On November 4, the spacecraft successfully executed a procedure to calibrate the power of the solar arrays. The method was identical to that used in a test in September, but this time the arrays were rotated to point 60 degrees away from the Sun instead of 45 degrees. With the arrays not pointed directly at the Sun, their power output was reduced to a level the spacecraft could measure.

October 31, 2008 - Dawn Completes Its Last Month of Thrusting

After mission controllers finished routine maintenance on components of the attitude control and ion propulsion subsystems on October 3, Dawn devoted the rest of the month to thrusting. On October 31, it completed almost all of the thrusting required for 2008.

September 30, 2008 - Dawn Conducts a New Solar Array Test and Routine Maintenance

Dawn continued to operate smoothly in September. Most of the month was devoted to ion thrusting, including September 27, the first anniversary of launch.

On September 22, operators conducted a revised version of the solar array test executed in July. This new test worked well, and it provided the data required to finalize a technique for calibrating the solar array power.

The spacecraft ended the month in a period of planned coasting that began on September 29. This time is used to perform periodic maintenance routines on some components.

August 30, 2008 - Dawn Reaches Greatest Distance from the Sun for 2008

Dawn spent most of August continuing to thrust with its ion propulsion system. On August 8, it reached its greatest distance from the Sun this year of 1.68 times Earth's average distance from the Sun. For the rest of 2008, it will gradually travel closer to the Sun. The spacecraft's elliptical orbit will never bring it as close to the Sun as Earth's orbit. In 2009, it will resume moving away from the Sun.

On August 26, the primary and backup science cameras were commanded to execute standard calibration procedures. The results verify that the cameras remain in good health.

July 31, 2008 - Dawn Conducts a Solar Array Test and Updates Software

Dawn completed another month of thrusting, as it passed outside the orbit of Mars. It stopped thrusting for two days this month to perform other activities.

Controllers conducted a test on July 21 of a method to determine how much power the solar arrays could produce (the spacecraft consumes less than the arrays generate while still this close to the Sun). The test did not provide the full set of calibration data that was wanted, but it yielded enough information to guide engineers to minor modifications of the design for the backup calibration opportunity.

On July 22, operators installed an update to software in one of the auxiliary computers to further harden it against the affects of space radiation.

June 30, 2008 - Dawn Switches to Ion Thruster #1 and Continues Thrusting

Dawn devoted most of the month to continuing to thrust with its ion propulsion system.

Based on the thermal tests conducted last month, engineers determined that it was safe to switch to ion thruster #1 this month. Therefore, on June 18, when it was time to resume thrusting after pointing its main antenna to Earth, Dawn began using that thruster for the first time since October. Data returned from the spacecraft the next day verified that all temperatures were within their required ranges.

May 30, 2008 - Dawn Conducts Routine Spacecraft Maintenance and Tests for Future Thrusting

Dawn devoted most of the month to continuing to thrust with its ion propulsion system.

A planned coast period from May 12 to 14 let the operations team conduct periodic maintenance. Some computer memory locations were checked and verified to be healthy. One of the three powered reaction wheels was turned off and the fourth wheel was powered on. All gyroscopes were powered on and operated for two days.

To investigate the temperatures that would be experienced for future long-duration thrusting with thruster #1, the spacecraft spent a few hours in the orientations that would be required. The resulting temperature data will contribute to determining when to switch from thruster #3 to #1.

April 30, 2008 - Special Activities Conducted During First Part of April

The month began with a non-thrusting period, scheduled to allow special activities:

The combined attempt to process the response from other software and commands sent by the mission operations team led to a conflict and the computer called "safe mode." After controllers returned the spacecraft to its normal configuration, ion thrusting resumed on April 14.

Meanwhile, engineers established that the software that interrupted the thrust test did so because of an unnecessary step. On April 21 they updated the software, removing that step.

The rest of the month was devoted to ion thrusting, as usual.

March 31, 2008 - Dawn Completes Another Month of Thrusting

Dawn thrust with its ion propulsion system for most of March, stopping once each week to point its main antenna to Earth. Almost 96% of the month was devoted to thrusting. By the end of March, the spacecraft was farther from Earth than the Sun.

February 29, 2008 - Thrusting Continues and Backup Framing Camera Tested

Dawn continued ion thrusting through most of February. On February 21 and 22, the backup framing camera was put through a series of tests to demonstrate its performance. The camera successfully completed all the steps, and analysis shows the instrument is healthy and operating as expected.

February 1, 2008 - Thrusting Continues and Software Updated in Main Computer

Dawn spent most of January continuing with ion propulsion thrusting. A cosmic ray that hit an electronic component on January 15 caused an interruption in thrusting for a few days. Thrusting halted on schedule on January 22 so the operations team could update the software in the main computer. The changes account for the increasing distance from Earth by lowering the speed of communications with Earth when the spacecraft enters "safe mode," the configuration called by software to resolve certain errors. Following the software changes, thrusting resumed on January 25.

January 2, 2008 - Interplanetary Cruise Continues

Dawn has continued thrusting with its ion propulsion system since December 17. Following programmed instructions, it interrupted thrusting on December 26 and on January 2 to point its main antenna to Earth to report on its status. All systems are performing well. Now that Dawn is in interplanetary cruise, these updates will occur less frequently.

December 17 - 21, 2007 - Interplanetary Cruise Begins

With the successful completion of the initial checkout phase of its mission, Dawn began the interplanetary cruise phase. While other activities will be conducted occasionally, the project's focus now is on thrusting with the ion propulsion system to reach asteroid Vesta (and later dwarf planet, Ceres).

December 10 - 14, 2007 - More Instrument Tests Completed

The backup science camera was powered on for the first time this week and verified to be healthy and operating well. The primary science camera and the visible and infrared spectrometer completed additional tests, and both instruments continue to perform extremely well.

December 3 - 7, 2007 - Additional Camera Tests and Software Loads Completed

The primary science camera was operated again, acquiring images of stars as a further test of its performance. All indications are that it is operating excellently. Software that had been uploaded earlier in the mission continues to work well, so the same software was loaded this week into some of the backup locations.

November 26 - 30, 2007 - Updated Software Loaded in Main Computer

This week was devoted to updating the software on the main spacecraft computer. This was planned before launch. Files were transmitted to the spacecraft, computer memory was checked, and other activities were conducted on Monday and Tuesday in preparation for rebooting the computer on Wednesday to start using the new software. On Tuesday night, the computer rebooted on its own. All diagnostic information has been returned from the spacecraft and the event is being investigated. With the new software operating as expected, controllers have verified that the spacecraft is healthy and activities are proceeding as scheduled.

November 19 - 23, 2007 - Main Antenna Checked Out and New Software Uploaded

This week, the spacecraft was commanded to use its main antenna for the first time and measurements showed that it is in fine condition. New software was installed in one of Dawn's computers (and its backup), correcting a minor bug that was discovered shortly after launch.

November 12 - 16, 2007 - More Ion Thrusting Tests Completed

The week-long systems test of interplanetary cruise thrusting completed successfully on Monday. The third ion thruster was tested this week, and like the other two, it performed perfectly. The thruster operated at 4 throttle levels, including full power. In a separate activity, the mission operations team powered off the reaction wheels to test pointing control with hydrazine thrusters during ion thrusting.

November 5 - 9, 2007 - Dawn Begins Cruise Thrust Test

To test the readiness of all systems for the interplanetary cruise phase of the mission (planned to begin in mid-December), Dawn is conducting a one-week execution of all the activities that will be typical of a week in that phase. As most of the time will be spent thrusting with the ion propulsion system, the spacecraft began thrusting on Monday and now has thrust for 4 days without interruption.

October 29 - November 2, 2007 - More Checkouts Completed

The operations team conducted tests of special modes of the attitude control system while the ion propulsion system is thrusting. All tests showed excellent performance. Two of the three ion thrusters have been fully checked out. Tests began with the third thruster this week, and all were completed successfully. The device that emits electrons to ionize xenon was heated to drive off contaminants, and then the thruster ionized xenon (but was not commanded to accelerate it). In addition, the gimbal system that points the thruster in the required direction was operated for the first time in flight. The first test of thrusting with this thruster is not scheduled to occur until after other spacecraft tests are completed.

October 22 - 26, 2007 - Second Ion Thruster Checkout Completed Successfully

The mission operations team completed the checkout of a second ion thruster this week. In one of the tests, the thruster was operated for 27 hours continuously at 5 different throttle levels, and in two other tests it was operated at maximum power for 4 hours each time. All spacecraft systems performed extremely well.

October 15 - 19, 2007 - Science Instruments Checked Out

Dawn's science instruments were powered on and given their first health checks this week. The gamma ray and neutron spectrometer, imaging camera, and visible and infrared mapping spectrometer all operated perfectly.

October 8 - 12, 2007 - Ion Propulsion System Testing Continued

The ion propulsion system performed extremely well as Dawn operated two of its three ion thrusters this week. Testing of the second thruster included placing the spacecraft in an orientation in which sunlight gradually warmed some other components more than mission controllers wanted, and the spacecraft was commanded to end the activity early. The spacecraft remained healthy throughout.

October 1 - 5, 2007 - Ion Propulsion System Tested

Mission controllers completed the configuration of the spacecraft for routine operations on September 29. During the week, all the steps were completed to prepare for the first test of ion thrusting.

September 24 - 28, 2007 - Dawn Launches!!

Dawn had a beautiful ride to space on September 27. Launch was delayed one day from bad weather, and liftoff was delayed 14 minutes from a boat in the range safety zone. Following liftoff at 7:34 am EDT, all systems performed well, and the operations team at JPL received signals from the spacecraft about two hours later showing that it was healthy. Since then, operators have been checking telemetry and configuring the spacecraft for routine operations.

September 17 - 21, 2007 - All Systems Preparing for Launch

Despite two days of delays from bad weather, the payload fairing was installed on the Delta rocket this week, and all systems are on schedule for launch on September 26. The operations team has now tested and verified all computer files necessary for launch and early operations. All that needs to be completed before launch is fueling and other final preparations of the launch vehicle.

September 10 - 14, 2007 - Dawn Spacecraft Returned to Launch Pad

On September 11, Dawn and the mated third stage were moved from Astrotech to Cape Canaveral's Space Launch Complex 17B where they were hoisted into place atop the second stage of the Delta launch vehicle. Brief tests of the spacecraft subsystems showed Dawn to be in good health. As part of the planned preparations for launch on September 26, the Kevlar cords that have held the solar arrays in their stowed position since prior to the planned June/July launch were replaced with fresh ones, and the new cords were adjusted to the correct tension for launch.

September 3 - 7, 2007 - Preparations for Mission Operations Continue

The operations team continued development of command sequences to be used during the first phase of the mission, known as initial checkout. These commands will guide the spacecraft through activities to provide data for engineers to use in evaluating the health and performance of all subsystems. Meanwhile, plans were completed for transporting the spacecraft back to the launch pad next week.

August 27 - 31, 2007 - Operations Team Simulates Launch and Operations

The operations team conducted simulations at JPL this week covering the last 16 hours of countdown, launch, and early operations. The simulation supervisor intentionally created some problems, all of which the team handled successfully.

August 20 - 24, 2007 - Launch Period Established

This week, NASA chose September 26 to October 15 as Dawn's launch period. Computer files that will be used during the final countdown were tested on the spacecraft, demonstrating that they work correctly.

August 13 - 17, 2007 - Dawn Team Continues Preparing for New Launch Date

The Dawn operations team continued to develop new sets of commands and other computer files for the spacecraft to use, accounting for differences between the previous launch period and the new September - October launch.

August 6 - 10, 2007 - Launch Coordinates Calculated

Engineers completed calculations of the coordinates needed for the rocket to deliver Dawn to space for a launch on any day from September 7 through October 15. (The dates for Dawn's launch period will be established soon.) These data will be used to program the rocket and to compute the open and close times of the daily launch windows. Now, with the details of the new trajectory early in the mission, the operations team is refining commands it will use during the first few weeks of Dawn's flight.

July 30 - August 3, 2007 - Spacecraft Tests Completed

Engineers completed a series of tests that verified all subsystems are healthy after transportation from the launch pad back to Astrotech.

July 23 - 27, 2007 - Spacecraft Moved to Astrotech

The spacecraft and third stage were removed from the launch pad and transported to a clean room at Astrotech. The first and second stages of the launch vehicle will remain on the pad (until liftoff).

July 16 - 20, 2007 - Preparations Continue for Removal of Spacecraft from Launch Pad

The payload fairing (the rocket's nose cone) has been removed. Tests confirmed that the third stage may be moved safely without removing any of its liquid propellant, clearing the way for the spacecraft and mated stage to be transported from the launch pad to Astrotech.

July 9 - 13, 2007 - Preparations Underway for September Launch

Work has begun to remove the spacecraft from the launch pad and return it to the clean room at nearby Astrotech Space Operations. (The spacecraft will remain mated to the third stage.) Launch trajectories for September are being designed

July 2 - 6, 2007 - Launch Rescheduled for September

Because of consistently bad weather and technical problems with launch vehicle tracking systems off the coast of Africa, Dawn's launch has been rescheduled to September.

June 25 - 29, 2007 - Dawn Moved to Launch Pad

The Dawn spacecraft and third stage were transported from Astrotech to Space Launch Complex 17B at Cape Canaveral and installed on the second stage. Final checkouts and preparations for launch continue on all three stages of the launch vehicle and the spacecraft.
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June 18 - 22, 2007 - Spacecraft Mated to Third Stage, and Second Stage Mated to First Stage

The spacecraft was connected to the third stage of the launch vehicle at Astrotech. At Space Launch Complex 17B, the second stage was lifted into place on the first stage.

June 11 - 15, 2007 - Hydrazine Loaded, Spin Test Completed, Operations Rehearsals Conclude

Hydrazine propellant, used as one means to rotate the spacecraft in space, was loaded. Spin tests were completed and balance masses were added to the spacecraft. During preparations for the spin tests, minor damage to the back of a solar panel occurred when a tool made inadvertent contact with it. The small affected area was patched over the weekend, and the process did not affect the launch date.

The mission operations team conducted more simulations of activities to be conducted in flight. The entire set of simulations to be executed before launch has now been completed.

June 4 - 8, 2007 - New Launch Date Set, Xenon Loaded, Operations Rehearsals Conducted

Because of delays in assembling Dawn's rocket at Cape Canaveral, Dawn's new launch date is July 7. Xenon propellant for the ion propulsion system was loaded into the spacecraft. Meanwhile, the mission operations team conducted additional simulations of launch and early flight activities.

May 28 - June 1, 2007 - Dawn Spacecraft Prepared for Fueling

In preparation for loading xenon and hydrazine propellants, the Dawn spacecraft was moved to the fueling area at Astrotech.

May 21 - 25, 2007 - Final Operations Test with Spacecraft and Attachment of Solar Arrays

The final mission operations test with the spacecraft was completed successfully. Dawn's solar arrays were attached to the spacecraft and the system for deploying them in space was given one final test, which went very smoothly.

The Dawn project had a large display at JPL's Open House, attended by more than 32,000 people.

May 14 - 18, 2007 - Telecommunications Tests Conducted and Observations of Vesta Completed

The spacecraft conducted a successful series of radio communications tests with MIL-71, the facility at the Kennedy Space Center that replicates a Deep Space Network station. The Hubble Space Telescope observed Vesta, the first of Dawn's two destinations.

May 7 - 11, 2007 - Spacecraft Alignments Completed and Launch Rehearsal Conducted

The alignment of spacecraft components was verified and finalized this week, ensuring that antennas, ion thrusters, scientific instruments, and other devices are properly oriented. With mission control at JPL connected to the spacecraft at Astrotech in Florida, mission controllers conducted another successful simulation of the final 4 hours of countdown, launch, and the first 4 hours of spacecraft operations once Dawn is in space. (This was a test of the procedures used to control the spacecraft and assess its condition; the launch vehicle was not involved.)

April 30 - May 4, 2007 - Comprehensive Performance Tests Completed

The spacecraft successfully completed two weeks of comprehensive performance tests. In these tests, each engineering subsystem and each instrument is operated extensively to verify it continues to function as required. The first run of the same tests was conducted in 2006, so engineers can verify that now that the spacecraft is in final preparation for launch, no unexpected changes have occurred as a result of the environmental tests or the shipment of the spacecraft.

April 23 - 27, 2007 - Mission Control Simulation of Ion Thrusting Completed

Mission controllers completed a four-day simulation of the procedures to be used to command and monitor the spacecraft for the first firing of the ion propulsion system after launch. This activity, known as an operational readiness test, used a simulator of the spacecraft to provide realistic responses to commands as well as signals for engineers in mission control to interpret. This simulation included the steps that would be followed to check the validity of the commands if the launch were delayed by a day, which would cause the alignment of the ion thruster relative to Earth to change. (A launch delay can occur as a result of bad weather or problems during the final countdown that cannot be resolved during the daily launch window.) Meanwhile, the final comprehensive performance tests are being conducted on the spacecraft in Florida to verify that each subsystem is still working correctly.

April 16 - 20, 2007 - Work on Spacecraft in Full Swing in Florida

Dawn's solar arrays, which convert sunlight into electricity, arrived at Astrotech Space Operations this week, where work continues on the spacecraft. (The solar arrays were removed from the spacecraft in December.) Version 6.1 of the software for the main spacecraft computer was loaded into the computer. Tests to show that software could be loaded onto the spacecraft while it is in space were completed successfully.

April 9 - 13, 2007 - Dawn spacecraft shipped to Florida

The spacecraft was trucked from the Naval Research Laboratory in Washington, DC to Astrotech Space Operations near Cape Canaveral this week. It was unpacked and moved into a clean room, and inspection showed it to be in fine condition after the trip.

April 2 - 6, 2007 - Completion of Additional Testing and New Launch Date

An acoustic test, in which powerful sound was directed at the spacecraft (similar to the noise of launch), was completed at the Naval Research Laboratory. This verified that the work to remove and reinstall the high voltage electronics assembly did not harm the spacecraft. To accommodate a change in the schedule for assembling the components of Dawn's Delta II launch vehicle, the launch date is shifted 10 days to June 30. The change will have no effect on mission objectives or science.

March 26 - 30, 2007 - High voltage electronics reinstalled and leak checks completed

The high voltage electronics assembly (the unit that governs the delivery of electrical power from the solar arrays to the onboard subsystems) completed testing in a thermal vacuum chamber at JPL and has been reinstalled on the spacecraft at the Naval Research Laboratory. Tests of the ion propulsion system and the reaction control system (the system that uses small conventional thrusters to aid in orienting the spacecraft in the zero-gravity of spaceflight) verified their integrity, with no leaks being found.

March 5 - 9, 2007 - Successful completion of tests coordinating flow of information between the Dawn spacecraft and ground systems network

Dawn has successfully completed all of the tests focused on the flow of information between the spacecraft and the network of ground systems that could be conducted before the spacecraft is in Florida. (Testing in Florida will be conducted with a facility near the launch site that replicates the characteristics of NASA's Deep Space Network communications facilities.) The content of version 6.0 of the software that runs in the main spacecraft computers was finalized this week.

December, 2006 - GRaND functional testing, reported by Tom Prettyman at LANL

December 16-17, we completed functional testing of GRaND following spacecraft (S/C) vibe and pyroshock. GRaND performed nominally and is ready to proceed to the next phase of environmental testing.

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October, 2006 - Solar Array Panels Attached to Dawn Spacecraft

Although the individual components of the spacecraft have already been tested, the point of the testing in Orbital Sciences Corporation's Environmental Test Facility is to verify that the fully assembled spacecraft will survive the rigors of launch and be able to fulfill its ambitious mission of exploration in deep space.

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September, 2006 - Dawn Spacecraft in Cleanroom at Orbital Sciences

Technicians complete the interior assembly of the spacecraft before installing the panels.

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August, 2006 - Dawn Spacecraft Placed in Thermal Vacuum Chamber

The Dawn spacecraft was moved into a vacuum chamber in the cleanroom and was baked for about a week for the purpose of driving off undesirable contaminants.

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March 27, 2006 - Dawn Mission Reinstated

NASA senior management announced a decision Monday to reinstate the Dawn mission, a robotic exploration of two major asteroids. "We revisited a number of technical and financial challenges and the work being done to address them," said NASA Associate Administrator Rex Geveden, who chaired the review panel. "Our review determined the project team has made substantive progress on many of this mission's technical issues, and, in the end, we have confidence the mission will succeed."

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March 2, 2006 - 2006 Mission Status

On March 2, 2006 NASA cancelled the DAWN mission. The Dawn spacecraft would have visited two of the solar system's largest asteroids, Ceres and Vesta, during a nine-year voyage.

October 3, 2005 - Mission Status Updates from the Dawn Project Manager

The second Framing Camera was delivered to Orbital, and bench checkout completed. Both Framing Cameras are waiting integration on the spacecraft. The first Power Processing Unit (PPU) for the ion propulsion system is complete, and has been delivered to Orbital. The second PPU is in environmental testing. The three gimbal assemblies for the ion thrusters have been delivered to Orbital, and the two outboard units have been mechanically integrated on the spacecraft. Spacecraft integration and test is progressing very well.

October 3, 2005 - Framing Camera Arrives

In late August 2005, the spacecraft Framing Camera 1 arrived at Orbital Sciences Corporation in Dulles, VA.

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Dawn’s mission director and chief engineer, Dr. Marc Rayman, takes you inside this remarkable solar system adventure. He presents a highly entertaining and accessible description of Dawn’s mission, starting with testing the spacecraft on Earth, then launching it and continuing through the entire deep-space journey.

Nontechnical and technical readers alike will appreciate the most comprehensive and lively account available anywhere of a real interplanetary mission, including not only what happens but also how engineers and scientists manage to accomplish such extraordinary feats.

Read the Journal