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NASA Cassini Significant Events 11/10/10 - 11/16/10

Status Report From: Jet Propulsion Laboratory
Posted: Monday, November 22, 2010

image The most recent spacecraft telemetry was acquired on Nov. 15 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, Nov. 10 (DOY 314)

Safing recovery efforts continued today with the uplink of D9 modules and opmode transitions to perform sequence activities that were halted with the safing event, but which were necessary for Orbit Trim Maneuver #266 (OTM-266), OTM-267, and a Radio Science Subsystem (RSS) Ka-band Operational Readiness Test (ORT). Files to power on the Cosmic Dust Analyzer (CDA), the Cassini Plasma Spectrometer (CAPS), and the Magnetometer (MAG) were also uplinked. The CAPS file is scheduled to execute just prior to the DSN pass on Saturday, Nov. 13.

A feature story called "Cassini Sees Saturn on a Cosmic Dimmer Switch" is available on the Cassini web site. It describes how like a cosmic light bulb on a dimmer switch, Saturn has emitted gradually less energy each year from 2005 to 2009, according to observations by the Cassini spacecraft. But unlike an ordinary bulb, Saturn's southern hemisphere consistently emitted more energy than its northern hemisphere. On top of that, energy levels changed with the seasons and differed from the last time a spacecraft visited Saturn in the early 1980s. For more information on this subject, link to: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20101110/

Thursday, Nov. 11 (DOY 315)

The Titan-73 (T73) flyby at 7921 kilometers altitude occurred today. No science data was taken since the spacecraft is still at the Earth-pointed safing attitude with no background sequence executing.

An article called "Saturn Then and Now: 30 Years Since Voyager Visit" was posted on the Cassini web site today. Ed Stone, project scientist for NASA's Voyager mission, remembers the first time he saw the kinks in one of Saturn's narrowest rings. It was the day the Voyager 1 spacecraft made its closest approach to the giant ringed planet 30 years ago. Scientists were gathering in front of television monitors and in one another's offices every day during this heady period to pore over the bewildering images and other data streaming down to NASA's Jet Propulsion Laboratory in Pasadena, Calif. For more information on this subject and images, link to: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20101111/

Friday, Nov. 12 (DOY 316)

Today, real time command procedure SCO-1786 was performed to load the A8.8.0 flight software into the backup AACS Flight Computer A (AFC-A) from the Solid State Recorder (SSR) for a second time, as a result of last week's safing incident. As a precaution, SSR auto repair was disabled during the load from the SSR. The loading of A8.8.0 flight software to the AFCs is now complete. DSS-14 had an emergency brake, a mechanical stop initially meant for DSS-13 but which inadvertently affected DSS-14, resulting in the loss of several Attitude and Articulation Control Subsystem (AACS) Memory Read Outs (MROs).

The SSR Instrument Expanded Block (IEB) loads for the Imaging Science Subsystem (ISS), the Visual and Infrared Mapping Spectrometer (VIMS), the Composite Infrared Spectrometer (CIRS), the Ultraviolet Imaging Spectrograph (UVIS), and CAPS were uplinked successfully along with the CAPS instrument direct IEB load today.

Saturday, Nov. 13 (DOY 317)

Additional instrument IEB loads for the S65 background sequence were uplinked today. In addition, a file to power on the remaining instruments - ISS, UVIS, CIRS, the Ion and Neutral Mass Spectrometer (INMS), the Radio and Plasma Wave Science Subsystem (RPWS), and the Magnetospheric Imaging Instrument Subsystem (MIMI) - was uplinked. All instruments are scheduled to be up by end of day Monday, Nov. 15. The AACS MROs for procedure SCO-1786 which were lost on DOY 316 were played back today.

Sunday, Nov. 14 (DOY 318)

A test of the backup reaction wheel assembly #3 (RWA-3) was uplinked today. This test will execute Nov. 16-19. RWAs 3 and 4 will be spun in opposite directions at two different rates to assess the health of RWA-3. Increasing concerns with wheel 1 are prompting the consideration of bringing wheel 3 back on line to support attitude control. Since wheel 4 is currently configured to have its spin axis parallel with wheel 3's spin axis, running them at equal speeds in opposite directions cancels out the momentum effects, hence avoiding the use of hydrazine and perturbations to the trajectory.

Monday, Nov. 15 (DOY 319)

OTM-266, the T73 clean-up maneuver scheduled for today, was cancelled. There was no impact to overall delta-V as the cost of cancellation was only about 3 mm/sec. Cancellation also freed up the tracking pass for safing recovery activities.

Instrument Operations (IO) sent commands to power on the ISS instrument and load flight software today.

Tuesday, Nov. 16 (DOY 320)

U.S. Cassini Scientist for a Day essays are being judged this week. Award ceremonies for winners in Australia, New Zealand, and Peru were held this week. A Cassini workshop proposal on Reading, Writing & Rings was accepted for the National Science Teachers Association annual conference that will be held in San Francisco in March 2011.

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