Cassini Significant Events 07/15/15 – 07/21/15

Cassini is currently orbiting Saturn with a period of 21.8 days in a plane inclined 0.5 degree from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on July 22 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 .

Cassini's activities this week were driven by the timed commands from the on-board, 10-week-long S90 sequence. Meanwhile, the Sequence Implementation Process teams worked on creating the sequences S91 and S92, and scheduled the activities for work on the S93 sequence. The latter is planned to go active on the spacecraft in February. Plans for Cassini's F-ring and Proximal orbits in 2016 and 2017, and the Grand Finale, proceeded as well.

Wednesday, July 15 (DOY 196)

The Composite Infrared Spectrometer (CIRS) finished a 14-hour observation that had started late the previous day, collecting infrared spectra from Saturn’s atmosphere to help study its chemical composition. Then, after an eight-hour tracking and communications session via the Deep Space Network (DSN), Cassini's Navigation team used the Imaging Science Subsystem (ISS) to take images of Saturn's large moon Rhea against the background of stars for optical navigation purposes.

Thursday, July 16 (DOY 197)

The spacecraft rotated slowly for 20 hours today while ISS precisely tracked Saturn's six-kilometer diameter irregular moon Bestla. This little object occupies a retrograde, highly inclined, and highly eccentric orbit that takes it more than 20 million kilometers from the planet. Bestla was named after a frost giantess from Norse mythology.

Eight hours into the Bestla observation, Cassini coasted through apoapsis, marking the start of Saturn orbit #219. It had slowed to 5,826 kilometers per hour relative to the planet at an altitude of 2.7 million kilometers -- more than twice the distance from Saturn out to Titan's orbit. Titan, by the way, is easily seen in small telescopes these nights, along with a beautiful view of the ringed planet.

The image that Cassini took of Pluto, near the time the New Horizons Spacecraft was making its closest approach last week, when all eyes were on the dwarf planet, is featured here: /resources/16211 .

Friday, July 17 (DOY 198)

CIRS performed a 13-hour observation to study the composition of Saturn’s atmosphere.

Saturday, July 18 (DOY 199)

The Cosmic Dust Analyzer (CDA) measured interstellar dust for 13.5 hours.

Sunday, July 19 (DOY 200)

ISS carried out an hour-long observation in the satellite orbit campaign, looking for small objects near Saturn. Upon completion, ISS and the Visible and Infrared Mapping Spectrometer (VIMS) did a two-minute storm-watch observation of Saturn. Finally, VIMS began a 17.5-hour observation of Saturn's faint E ring and G ring while they were sunlit at a phase angle of 105 degrees. CIRS rode along.

Two crescent moons grace the Saturnian sky in this featured image: /resources/16213 .

Monday, July 20 (DOY 201)

The only science observation that Cassini started today was a two-minute ISS storm-watch on Saturn. Otherwise, the spacecraft remained busy with an eight-hour instrument calibration activity and then a nine-hour DSN session.

Tuesday, July 21 (DOY 202)

ISS, CIRS and VIMS performed a 90-minute observation in the Titan monitoring campaign, from a distance of 2.8 million kilometers. Next, ISS took a quick storm watch, and then an hour-long satellite orbit campaign observation. After this was finished, CDA turned the spacecraft and performed a ten-hour measurement of dust that orbits Saturn in the retrograde direction.

Along with all of the other observations described this week, the direct-sensing Magnetospheric and Plasma Science (MAPS) instruments collected data nearly continuously, reporting on conditions in the spacecraft's immediate environment.

During the past week, the DSN communicated with and tracked Cassini on nine routine occasions, using deep space stations in Spain, California and Australia. A total of 17 individual commands were uplinked, and about 1,020 megabytes of telemetry data were downlinked and captured at rates as high as 124,426 bits per second.

This illustration shows Cassini's position on July 21: https://space.jpl.nasa.gov/cgi-bin/wspace?tbody=-82&vbody=1001&month=7&day=21&year=2015&hour=23&minute=55&fovmul=1&rfov=45&bfov=30&brite=1&showsc=1&showac=1 .

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/ .