Cassini Significant Event Report

For Week Ending 12/06/02

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, December 4. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the spacecraft's position and speed can be viewed on the "Present Position" web page.


The C34 sequence concluded this week with the completion of the Probe Relay Test #5, uplink of the C35
background sequence, Radio and Plasma Wave (RPWS) Science High Frequency Receiver calibrations and
high rate cyclics, a Reaction Wheel Assembly (RWA) slow-speed readout, clearing of the ACS high-water
marks, and an autonomous Solid State Recorder Memory Load Partition repair.


The Probe Relay Test was considered to be a limited success. All transmissions to the spacecraft were
received and processed properly, but problems at the DSN station prevented all test objectives from being fully
met.


The C35 background sequence began execution on Saturday, 30 November. Initial spacecraft activities
included a number of RWA activities including transition from Reaction Control Subsystem to RWA control, an
RWA unload, a slow speed readout, and an exercise of RWA #4. Engine Gimbal Actuator and Backup ALF
Injection Loader maintenance were also performed.


Instrument activities included uplink of the RPWS looper program, a Visual and Infrared Mapping
Spectrometer and Ultraviolet Imaging Spectrograph solar port observation, exercising of the Magnetospheric
Imaging Instrument (MIMI) Low Energy Magnetospheric Measurement Subsystem motor, restoration of the
MIMI Ion and Neutral Camera HV levels, a Cosmic Dust Analyzer high rate detector calibration, and a
number of Radio Science Subsystem activities.


During the final pass before the end of C34 and the beginning of C35, Cassini Plasma Spectrometer (CAPS)
had a channel go into alarm for low temperature. Subsequent analysis determined that the commands to bring
CAPS out of sleep after the Probe test were built incorrectly. An Immediate/Delayed Action Program was
built and sent to the instrument to stop the actuator, reset it, and set the RAM to zero. After uplink the CAPS
team reported that the transition sequence was triggered and successfully re-configured the instrument. CAPS
is now running in a fully configured and nominal state.


The Cassini Program hosted a week of Huygens meetings at JPL. Events included the Huygens Descent
Trajectory Working Group meeting, a Probe Checkout #10 Review, and a Quarterly Progress meeting. Some
of the topics discussed included activities status, entry angle issues, mission timeline and schedules, and
navigation and pre-heating implementation studies.


Rescheduling of the SIRTF launch to mid April '03 has removed potential conflicts with DSN coverage for the
Cassini ACS/CDS flight software checkout in C36. DSN schedule impacts in C37 are unknown. Mission
Planning will track DSN coverage for that time frame as Trajectory Correction Maneuver 19 is scheduled to
occur on May 1. Additionally, some Cassini trained ACE personnel with SIRTF may now be available to
support tracks for the Gravitational Wave Experiment.


An engineering prototype version of the electronic command request form (eCRF) v1 was released this week.
The system will be used in parallel with Cassini's existing process. Full conversion to eCRF will occur in late
2003.


Mission Assurance and European Space Agency (ESA) Risk Management personnel met this week to discuss
the Risk Management process/philosophy on Cassini, and determine how best to work the ESA/Huygens
Probe portion of the process. Probe Mission risks currently identified in the Cassini Significant Risk List clearly indicate a very orbiter-centric view. This was the first of several meetings to be conducted in the coming months in an effort to effectively capture and document risks from an ESA/Huygens Probe perspective.



Additional information about Cassini-Huygens is online at http://saturn.jpl.nasa.gov.


Cassini will begin orbiting Saturn on July 1, 2004, and release its piggybacked Huygens probe about six months later for descent through the thick atmosphere of the moon Titan. Cassini is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Office of Space Science, Washington, D.C.


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