Cassini Significant Events 03/04/2015 – 03/10/2015

Cassini is currently orbiting Saturn with a 31.9-day period in a plane inclined 8.5 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on March 11 using one of the 34-meter diameter Deep Space Network stations in Australia. 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 .

The S88 command sequence, which has been registered in the spacecraft's memory for nearly a month now, controlled most of Cassini's activities again this week. Meanwhile, the Sequence Implementation Process teams, led from JPL with members in the U.S., Germany, Italy, and the U.K., continued working to develop the 10-week command sequences S89 and S90; activities for S91 are on the calendar. Planning work continued for next year's mission's activities, including the start of the F-ring orbits which will begin in S97, and the 2017 Grand Finale starting in S99.

Wednesday, March 4 (DOY 063)

The flight team sent real-time commands today, based on the latest navigation solutions, for Cassini to perform Orbit Trim Maneuver (OTM) 405. The maneuver had the spacecraft turn and fire its small rocket thrusters for 100 seconds, producing a change in velocity of 99.7 millimeters per second. This adjusted Cassini's flight path for the Titan T-110 fly-by on March 16. With the OTM completed, the Cosmic Dust Analyzer (CDA) was given control of spacecraft pointing for 15 hours to carry out an observation of dust that orbits Saturn in the retrograde direction.

Thursday, March 5 (DOY 064)

Late in the day, following a communications session via Deep Space Network (DSN), CDA began a 37-hour observation, continuing its retrograde science campaign.

Friday, March 6 (DOY 065)

While CDA was in control of spacecraft pointing, the Magnetospheric and Plasma Science instruments continued collecting data about their immediate environment.

Saturday, March 7 (DOY 066)

Today's DSN pass was fairly typical. Just as the 70-meter diameter Deep Space Station 43 in Canberra, Australia, finished turning its six million pounds of steel towards Saturn, which was rising in the east, the 8 GHz radio signal from Cassini arrived Earth. It had taken 80 minutes 57 seconds to reach across the distance. Cassini's data rate stepped up to 110,601 bits per second (due to timed commands in S88), and the telemetry flowed to JPL, where the flight team was watching: all's still well on Cassini. After a few minutes, Station 43 turned on its 18 kW transmitter, sending an 8 GHz radio tone with its frequency based on a stable hydrogen-maser standard. After the 162 minutes of round-trip light-time, Cassini's Navigation team began receiving six hours of coherent Doppler and ranging -- the tracking data they need to accurately solve for the spacecraft's motion in Saturn orbit. Mid-day, Cassini's telemetry rate stepped up to 142,201 bits per second (with Saturn high in the sky, Cassini's signal had to deal with less interference from Earth's atmosphere).

After nine hours spent communicating via the DSN, Cassini turned to point the Imaging Science Subsystem (ISS) to Saturn for a two-minute storm-watch observation. It then turned to point the Composite Infrared Spectrometer (CIRS) to the sunlit side of Saturn's A ring for nine hours, to obtain low-resolution thermal infrared spectra. The Visible and Infrared Mapping Spectrometer (VIMS) took advantage of its shared pointing and made observations in ride-along mode. The data will help determine the chemical composition of ring particles.

Sunday, March 8 (DOY 067)

Cassini's Navigation team used the ISS for 90 minutes to take images of Saturn's satellite Dione against its background of stars for optical navigation purposes. This will help them prepare for the Dione encounters later this year. Once the "opnav" imaging was complete, CIRS took back pointing control for 19 hours, studying composition of the C-ring particles by gathering low-resolution thermal infrared spectra. VIMS rode along.

Monday, March 9 (DOY 068)

ISS made another quick Saturn storm watch, and then spent 19.5 hours tracking Saturn's bright, thin F ring to make a movie at low resolution, while VIMS rode along. This F ring observation repeated on the following day for 13 hours.

Saturn's moon Iapetus puzzled Cassini the scientist in 1671, and it puzzled Voyager scientists in 1980 and 1981. With data from Cassini the spacecraft, scientists believe they have solved the mystery of its naturally two-tone surface:
/resources/16168 .

Tuesday, March 10 (DOY 069)

During the past week, the DSN communicated with and tracked Cassini on six occasions, using stations in California and Australia. A total of 135 individual commands were uplinked, and about 1,346 megabytes of telemetry data were downlinked and captured at rates as high as 142,201 bits per second.

A late-breaking news feature describes hydrothermal activity that is likely to be occurring on the sea floor of Saturn's tiny moon Enceladus:
http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20150311 .

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This illustration shows Cassini's position on March 10:
https://space.jpl.nasa.gov/cgi-bin/wspace?tbody=-82&vbody=1001&month=3&day=10&year=2015&hour=23&minute=55&fovmul=1&rfov=30&bfov=30&brite=1&showsc=1&showac=1 .
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Milestones spanning the whole orbital tour are listed here:
http://saturn.jpl.nasa.gov/mission/saturntourdates .
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