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NASA Cassini Significant Events 10/27/10 - 11/02/10

Status Report From: Jet Propulsion Laboratory
Posted: Friday, November 5, 2010

image The most recent spacecraft telemetry was acquired on Nov. 2 from the Deep Space Network tracking complex at Canberra, Australia. 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: http://saturn.jpl.nasa.gov/mission/presentposition/.

Wednesday, Oct. 27 (DOY 300)

An encounter strategy meeting was held today to cover the period between Nov. 11 and Nov. 30, Titan flyby T73 and Enceladus flyby E12, and maneuvers 266-268.

Last week, 65 teachers at the California Science Teachers Association's annual conference in Sacramento attended a professional development session on Cassini's "Reading, Writing & Rings" science and language arts curriculum and the follow-on curriculum in development, "Our Solar System Through the Eyes of Scientists".

Today was the deadline for the Fall 2010 Cassini Scientist for a Day essay contest. Over 1,000 U.S. students from 67 classrooms in 23 states participated in the essay contest. Thirty countries on six continents are running parallel Cassini Scientist for a Day essay contests as well.

Thursday, Oct. 28 (DOY 301)

Port 3 products were due today as part of the S66 Sequence Implementation Process (SIP). The products will be merged and sent out to the flight team for review.

This week in science, the Visual and Infrared Mapping Spectrometer (VIMS) concluded its 37 hour exoplanet transit observation. The Cosmic Dust Analyzer (CDA) completed two 29 hour interstellar dust campaigns. The Magnetometer performed an 8 hour calibration while rolling about the X-axis of the spacecraft. The Magnetospheric and Plasma Science (MAPS) instruments performed a survey. Imaging Science (ISS) performed another observation in its Satellite Orbit Campaign, completed a 16.5 hour observation of the moon Kari, and a 16.5 hour observation of the moon Bergelmir. ISS, VIMS, and the Composite Infrared Spectrometer (CIRS) performed another observation in the Titan monitoring campaign.

Friday, Oct. 29 (DOY 302)

The Spacecraft Operations Team (SCO) sent real time commands today in support of Attitude and Articulation Control Subsystem (AACS) activities. The SCO team uplinked files to clear high water marks, perform a reset of the backup AACS Flight Computer (AFC) B, and loaded AACS flight software version A8.8.0 from the non-equivalent partition of the Solid State Recorder (SSR), completing the installation of A8.8.0 onto the backup AFC-B.

Commands were radiated over Madrids DSS-63 today in support of the S64 CDA Rhea threshold setting, which will start executing on the spacecraft on Nov.10.

Sunday, Oct. 31 (DOY 304)

Reaction Wheel Assembly (RWA)-1 low rpm test #3, the last of the three planned RWA tests, took place today. RWA-1 was set to +400 rpm for a period of about eight hours to characterize behavior at this wheel speed. Results from all three tests are the subject of analysis to better understand the cause of higher than expected friction levels.

Monday, Nov. 1 (DOY 305)

Target Working Team and Orbiter Science Team integrated products for S68, covering orbits 147 through 150 in April 2011 through July 2011, were delivered today. The integrated products are in their final form and no re-integration is planned. The Sequence Implementation Process will kick off on November 17. The instrument teams are working on the pointing designs for this sequence.

Attitude control was switched from reaction wheels to thrusters today to remain Earth-pointed for the next few days in order to perform an AACS flight software update while simultaneously providing a rest period for the reaction wheels. A real time command SCO procedure was performed for the AFC Swap and Parameter Update which executed successfully today. AFC-B is now prime using the new flight software load A8.8.0. This is the first AFC swap in six years; the last time was to load the Probe relay flight software load in October 2004.

A news release called "Cassini Sees Saturn Rings Oscillate Like Mini-Galaxy" is available on the Cassini web site. Scientists believe they finally understand why one of the most dynamic regions in Saturn's rings has such an irregular and varying shape, thanks to images captured by NASA's Cassini spacecraft. And the answer, published online today in the Astronomical Journal, is this: The rings are behaving like a miniature version of our own Milky Way galaxy. For more information on this subject and images, link to:
http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20101101/.

Tuesday, Nov. 2 (DOY 306)

The results of a study of maneuvers near end of mission were presented at the Mission Planning Forum this week. The topics were the delta-v impact of accidental burn-to-depletions and a possible planned burn-to-depletion near the end of mission. An accidental burn-to-depletion occurs when either insufficient fuel or oxidizer remains to produce the thrust level required during a main engine maneuver. The study looked at the delta-v impact of completing the interrupted maneuver at a later time using hydrazine and the RCS thrusters. A planned burn-to-depletion concept was also discussed in the event that bipropellant remains at the very end of the mission. This burn, if performed, would be done during the last proximal orbit to determine how much usable propellant remained in the tank. The study identified times during the last orbit where the burn could be performed and impact into Saturn's atmosphere would still be assured. There are many issues to consider for both of these concepts and the topic will be studied in more detail when the project looks to plan the later segments of the mission.

The SCO team performed a real time command procedure to load backup AFC-A with AACS A8.8.0 from the non-default SSR.

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