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Cassini Significant Events 06/24/15 – 06/30/15

The spacecraft continues to be in an excellent state of health with all of its subsystems operating normally except for the instrument issues described at http://saturn.jpl.nasa.gov/news/significantevents/anomalies .

Timed commands from the on-board, 10-week-long S89 sequence controlled most of Cassini's activities this week. Meanwhile, Sequence Implementation Process teams worked on creating the 10-week command sequences S90, S91 and S92. The latter is planned to go active on the spacecraft on Nov. 25 of this year. Plans for Cassini's F-ring and Proximal orbits in 2016 and 2017 and the Grand Finale proceeded as well, incorporating decisions made during the 66th Project Science Group meeting last week.

Wednesday, June 24 (DOY 175)

The Cosmic Dust Analyzer (CDA) began controlling the spacecraft's attitude for five days of planned observations. One of the goals is to identify the source of fast-moving nano-particles that are modulated by Saturn’s rotating magnetosphere. Another goal is to identify and characterize dust coming in from interstellar space. CDA's science activities between now and late Sunday were interrupted only by planned spacecraft engineering activities, and routine sessions with the Deep Space Network for two-way radiometric tracking and digital communications.

Thursday, June 25 (DOY 176)

Without perturbing CDA's activities, the Magnetospheric Imaging Instrument (MIMI) began a magnetospheric and plasma science survey that lasted the rest of the week.

Near the end of the day, Cassini coasted through apoapsis, the farthest point of its orbit about the ringed gas giant. It had slowed to 5,984 kilometers per hour relative to the planet, and reached an altitude of 2.49 million kilometers in Saturn's equatorial plane; this is about twice the distance out to Titan's orbit. Thus began Cassini's orbit #218; there are 75 more orbits of Saturn planned before the mission's Grand Finale in September 2017.

Friday, June 26 (DOY 177)

Today, the planned engineering activity that interrupted CDA's science data collection was an Orbit Trim Maneuver (OTM). Commands had been prepared and uplinked the day before, based on the Navigation team's latest orbital solutions. When the time came today, the spacecraft turned to the proper attitude and fired its four small aft-facing thrusters for 71 seconds. This OTM-414 provided the required change in velocity of 70 millimeters per second, targeting to the July 7 flyby of Titan known as T-112.

Saturday, June 27 (DOY 178)

Saturn continues to be well placed in the sky all night for anyone to see. Using a small telescope, Titan is also clearly visible, and some of Saturn's other large moons can be noticed as well. With its equatorial plane canted down towards the south, the main rings can be seen spanning a distance of 274,000 kilometers edge to edge. For comparison, the distance from Earth to our Moon is 384,000 km, and from Saturn to Titan is 1.2 million km -- roughly three ring-diameters out from Saturn.

Sunday, June 28 (DOY 179)

All during the week, the Radio and Plasma Wave Science instrument (RPWS) has been acquiring data on Saturn's natural radio emissions, as well as on the interaction between Saturn's magnetic field and the solar wind. An image from 2007 illustrates some of the capabilities and applications of this instrument:
/resources/13885 .

Monday, June 29 (DOY 180)

The Navigation team used Cassini's Imaging Science Subsystem (ISS) for 90 minutes to take images of Saturn's small icy moon Mimas against the background of stars, for optical navigation purposes. ISS then controlled spacecraft pointing for 31 hours to observe Saturn's irregular moon Kiviuq. As described on May 10 (http://go.nasa.gov/1LDtVGC), Kiviuq is a small, dark-surfaced object that orbits Saturn in a distant, inclined, eccentric orbit.

Saturn's innermost ring, the D ring, is not visible from Earth in most telescopes. Its particles revolve about the giant planet in as little as 4.8 hours. Spirals in the D ring are featured in an image today:
/resources/16205 .

Tuesday, June 30 (DOY 181)

Eleven years ago today (Pacific Daylight Time), the Cassini spacecraft, carrying the Huygens Probe, turned to face its high-gain antenna dish forward as a protective shield, and proceeded to fly through Saturn's ring plane for its first time. It then turned back about 180 degrees to face its main engine forward. After firing the liquid bi-propellant-fed rocket engine for 96 minutes, the spacecraft had slowed down enough to allow the ringed planet’s gravity to capture Cassini-Huygens as Saturn's first orbiting spacecraft.

During the past week, the DSN communicated with and tracked Cassini on nine routine occasions, using deep space stations in California and Australia. A total of 264 individual commands were uplinked, and about 1,030 megabytes of telemetry data were downlinked and captured at rates as high as 142,201 bits per second.

Milestones spanning the whole orbital tour are listed here: http://saturn.jpl.nasa.gov/mission/saturntourdates .

Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at:
http://saturn.jpl.nasa.gov/mission/presentposition/ .