Cassini Significant Events 09/17/08 - 09/23/08

September 25, 2008

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired on Sept. 23 from the Deep Space Network tracking complex at Madrid, Spain. The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at:

Wednesday, Sept. 17 (DOY 261):

The Fall 2008 edition of the Cassini Scientist for a Day essay contest was launched on Sept. 16. The contest is open to all grade 5-12 students in the United States. Participating students will be competing in one of three groups, grades 5-6, grades 7-8, and grades 9-12. Targets for this contest are Tethys, Titan, and Mimas. Students will write a 500-word essay defending their selection of one of these three targets. The essay contest has a deadline of Oct. 30, 2008, and Cassini will obtain the images on Nov. 26, 2008. Winners will be invited to participate in a teleconference with Cassini scientists. For more information, videos, and complete contest rules, teachers and students can visit the contest website at:

A flyer summarizing the contest can be found at:

Any questions regarding the contest should be e-mailed to:

Non-targeted flybys of Pandora, Mimas, Calypso, and Daphnis occurred today.

The final integrated S49 sequence segments for orbits 106 - 110 are due from the Target Working Teams and Orbiter Science Teams today. These integrated products will be in sequence level form and ready for the start of Science Operations Plan implementation. Science teams will begin work on their pointing designs on Sept. 19. The final Cassini DSN station requests will also be delivered to the DSN schedulers on the 19th. The official kick-off meeting for S49 is scheduled for Oct. 1.

Wednesday was a busy day on the spacecraft as Ultraviolet Imaging Spectrograph (UVIS) and Visual and Infrared Mapping Spectrometer (VIMS) observed stars passing behind the rings, the Composite Infrared Spectrometer (CIRS) observed Enceladus in eclipse behind Saturn to look for sources of endogenic energy in the south polar region, the Magnetospheric and Plasma Science (MAPS) instruments collected at increased rates to observe auroral magnetosphere and Saturn Kilometric Radiation source regions, and the Imaging Science Subsystem (ISS) Narrow Angle Camera (NAC) performed non-contiguous azimuthal scans of the rings targeted on a particular ringlet, the A ring group, and observed Enceladus at an intermediate phase angle to monitor plume activity.

Thursday, Sept. 18 (DOY 262):

The Main Engine (ME) cover was opened today. It has been closed for the last 25 days, having been closed (deployed) on Aug. 24. This completes the 44th cycle of the cover. During that time there were only a few potential dust hazards, but since the time frame included Superior Conjunction - a time of possible limited communication with the spacecraft - and the Project has a policy of limiting the number of cover cycles, it made good sense to just keep it closed until the next main engine burn. The next cover deployment is on Sept. 21. For that cycle the cover will remain closed for four days and will reopen on Sept. 25.

Friday, Sept. 19 (DOY 263):

Reading, Writing and Rings (RWR) has been published in the September 2008 issue of the National Science Teachers Association (NSTA) journal "Science and Children," and awarded a SciLinks from the National Science Teachers Association. This means key textbook subjects will be linked to RWR as an NSTA approved web page. SciLinks has registered more than 156,000 teachers and nearly 640,000 students. In addition, representatives from the publication Education Week shadowed our partners, the Bay Area Writing project, as they began beta testing the outreach follow-on language arts product "Through the Eyes of a Scientist." Education circulation has about 725,000 registered users.

Science today began with nine hours of VIMS observing as a star occulted the outer C Ring. After a 9-hour downlink, CIRS continued its campaign to thermally map and monitor the rings. Finally today completed with an ISS lit-side low phase ring movie to search for spoke periodicities.

Saturday, Sept. 20 (DOY 264):

Commands were sent to the spacecraft today for Orbit Trim Maneuver #164a, a real-time reaction wheel bias to execute over the 164a backup pass, Live Update #2 to execute on DOY-268, and a CDA ring plane crossing activity for DOY-269.

Orbit Trim Maneuver (OTM) #164a was performed today. This is the cleanup maneuver from the Enceladus 4 encounter on Aug. 11. The main engine burn began at 1:15 PM PDT. Telemetry immediately after the maneuver showed the burn duration was 5.3 seconds, giving a delta-V of 0.88 m/s. All subsystems reported nominal performance after the maneuver.

On Sunday the spacecraft will again be primarily taking data with the NAC. The camera will begin with orbit determination observations of several small satellites, including Pan, Epimethius, Prometheus, and Janus. Next an image will be taken as part of a Titan cloud monitoring campaign. Then the camera turns to Rhea for a low phase angle observation with UVIS riding along. Coming into the home stretch, three optical navigation images are taken, and to end the day, images of Mimas with UVIS again riding along are planned.

Monday, Sept. 22 (DOY 266):

Teams made the first delivery today as part of the Science Operations Plan process for S48.

Tuesday, Sept. 23 (DOY 267):

An AACS Periodic Engineering Maintenance was completed on the spacecraft today. In addition, a friction test of the backup reaction wheel (RWA) was performed. For this test, performed every six months, the RWA is spun up to 600 rpm in both the clockwise and counterclockwise directions and timed as it is allowed to run down to zero.

The third potential Live Update for S44 would cover DOY 275-277 and modify vectors for Saturn and Tethys. Science Planning has already performed some analysis and finds the errors are minimal, and is recommending a *NO-GO* for the live update. CIRS, ISS, and UVIS have observations of designated targets during this period and will be responding over the next day or so with their inputs to the decision.

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