Cassini Significant Event Report

For Week Ending 12/03/04

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Monday, December 1. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" web page located at .

The Ultraviolet Imaging Spectrograph (UVIS) continued to monitor Saturn's inner magnetosphere in neutral and ion photon emissions to derive the distribution and density of atomic and molecular species. UVIS also continued to examine the F Ring to monitor changes in ring reflectance properties.

RADAR performed a Radiometric calibration of their subsystem by examining microwave sources including the Sun and Saturn among others.

On-board activities this week included an Inertial Reference Unit calibration, Reaction Wheel Assembly unload, and the uplink of files for later execution for Probe Battery Depassivation #2, a Cassini to Titan vector update on 2004-346, Imaging Science Subsystem (ISS) sequence count rollover error patch, and a Magnetospheric Imaging Instrument (MIMI) STARE mode for Titan b.

The primary activity this week was the execution of the final Huygens Probe checkout (PCO). This in-flight checkout procedure was the last one planned before separation of the Huygens probe from Cassini in about three weeks. The preliminary analysis of the real-time data received showed all events in the checkout procedure occurred as, and when, expected. For more information link to:

Since the start of Approach Science in January of this year, 29509 ISS images and 6323 Visual and Infrared Mapping Spectrometer cubes have been acquired.

The project has decided to raise the flyby altitudes of the Titan 5 and Titan 7 encounters from 950 km to 1025 km. The Titan Atmospheric Model Working Group's Ta workshop on November 15 and subsequent discussions and analyses by both scientists and engineers have produced results that render 950 km flybys questionable without at least one intermediate flyby between 1174 km and 950 km. The 1025 km altitude is low enough to provide a clear indication of spacecraft safety, or not, at 950 km, yet high enough to be certain to be safe.

Preliminary indications from the Navigation team are that this action can be taken at little or no delta-V cost or impact to the occultation sequences or subsequent encounters. The altitude of Titan 4 - currently at ~2500 km - lowers slightly, and timing changes to all encounters exclusively from this change are less than one minute. The navigation team will be releasing a new spacecraft ephemeris shortly.

Spacecraft Operations Office (SCO) personnel reran the Probe Relay and Playback portion of the end-to-end test on Monday and Tuesday of this week. The Integrated Test Lab rerun was requested to collect additional redlines for the Probe Relay sequence and to verify the changes made to SCO procedures as a result of the earlier end-to-end simulation.

Development continues for the S06 Titan-b live Inertial Vector Propagator (IVP) update. Files for the update were transferred to the Integrated Test Laboratory (ITL) and a test performed from November 24 through November 28. Initial assessments from both CDS and ACS were that the test was a success. A meeting was held on November 30 where the Titan-b flyby live IVP update files were approved and on December 1 were uplinked to the spacecraft.

Sequence development is ongoing for tour sequences S07 through S12, and S37 through S41.

A Project Briefing and Waiver Disposition meeting was held for S09. S10 Preliminary port 1 products were delivered as part of the Science Operations Plan Update process (SOPU). The products were merged and the reports published.

The S11 aftermarket process concluded this week. Products will be provided from this activity to the leads for the SOPU process, which kicks off on December 9.

An Assessment meeting was held for S12 to review all of the requested changes to the sequence. It looks like all of the requested changes can fit within the available resources. Unless the Target Working Teams and Orbiter Science Teams recommendations change over the next couple of weeks, it is likely that the decision meeting scheduled for December 14 will be canceled.

A wrap-up meeting was held last Wednesday for tour sequences S37/S38 as part of the Science Operations Plan Implementation (SOPI) process. These sequences have now been archived and will begin the aftermarket process in August of 2007. Preliminary port #1 occurred as part of SOPI for S39/S40. The products were merged and the reports published.

An ISS flight software patch to avoid warm restarts was approved last week by the Project. The uplink files were prepared and approved for uplink. The patch will be installed into the instrument on December 3.

A Delivery Coordination Meeting was held for Radio Science Subsystem (RSS) software POSTLB, the final software tool in the RSS tool suite. This tool does post-processing of the Inertial Vector Definition and Doppler files generated by LMTTRK and BISTAT. It removes pointing discontinuities at ingress and egress during occultation observations.

On November 20, a Bay Area Writing Project team member introduced 50 NASA education representatives to, "Reading, Writing, and Rings" at a nationwide workshop in Houston, Texas. These representatives train educators throughout the country on NASA materials.

Saturn Observation Campaign members in Spain and Ireland published articles in their local magazines about the Cassini Mission to Saturn.

On November 27 the Los Alamos Monitor did a follow up on Girl Scout Troup 128 who seven years ago signed on to a 3.5 billion km voyage out beyond the moon and nearby planets. Now their names are among 616,400 handwritten signatures from 81 countries on board the Cassini orbiter, as it settles in around the great ringed world of Saturn, the sixth planet from the Sun.

Check out the Cassini web site for the latest image advisory: Cassini Shows Grandeur of Two Saturn Moons. The pictures are available at

Cassini images made Astronomy Picture of the Week three times last week with images of Tethys and Dione, and a Radar Image of Titan.