Cassini Significant Event Report

For Week Ending 05/03/02

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, May 1. 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.

This week marks the four year anniversary of the Cassini Venus 1 flyby. Onboard activities this week included Periodic Instrument Maintenance for the Ultraviolet Imaging Spectrograph, Imaging Science Subsystem decontamination activity #1, clearing of the ACS high water marks, and an autonomous CDS Solid State Recorder
memory load partition repair.

The C32 sequence was approved at the Preliminary Sequence Integration and Validation meeting. The sequence will be uplinked and begin execution next week. As part of validation for the new command system, C32 will be radiated using the new Spacecraft Message File format rather than the old Command Packet File. C32 will be the largest file sent so far using the new command system.

Cassini participated in a DSN array test at the DSS complex in Goldstone, California. Cassini results indicated the test was a success with a 1 dB gain in signal level and 3 dB gain in telemetry signal to noise ratio. DSN personnel are still analyzing test data.

Science Planning is preparing for the kickoff of the first tour Science Operations Plan (SOP) implementation activity. This process will implement sequences 9 and 10 of the tour. An SOP implementation schedule has been developed using two concurrent processes and two sequences per process approach, and a kickoff package is being generated.

The Huygens Implementation team held its second quarterly progress meeting at Alcatel in Cannes. The team has agreed upon a set of flyby conditions that are independent of the decision to pre-heat the probe prior to entry into Titan's atmosphere. The decision on whether to pre-heat the probe will be made later after a complete assessment of the impact can be made by the probe instruments. Other topics discussed were link budget updates, mission analysis and robustness studies, and entry sensitivity studies.

The Navigation team has released a new reference trajectory for the orbital tour and the remainder of interplanetary cruise. This new trajectory includes the latest flyby geometry for the revised Huygens mission and the final icy satellite adjustments and changes made for G-ring crossings. This trajectory will serve as the reference for the Science Operations Plan that will begin development in May.

An updated strawman presentation of DSN coverage to be requested for revs 20 through end of tour was presented at this week's Mission Planning Forum. Discussion included the plan's consistency with overall data volume requirements, navigation tracking requirements, orbital trim maneuver placement, sequence boundaries, Target Working Team boundaries, and engineering events.

A meeting was held to finalize Uplink Operations development of the Automated Sequence Processor. A preliminary version will be available in the fall of 2002, with a final version being delivered in fall of 2003. This software subsystem will be a Cassini adaptation of what is already in use within the Mars Program. It will allow for a more automated way to process real-time command requests from remote users.

Mission Assurance coordinated the first Quarterly Risk Team Meeting, to assess and re-assess risks in the Cassini Significant Risk List. This meeting produced some valuable discussion on risk issues and focused on addressing Cruise Risks. Four new consumables risks were identified, for addition to the Significant Risk List (SRL). Future Risk Team Meetings will be scheduled to address SOI, tour, and Probe mission risks.

Mission Assurance completed a trend analysis of sequence and command errors experienced since launch. Error rates were trended with the rate of uplink activity to the spacecraft. Trend analysis indicates that the error rate has decreased since launch, and despite periodic fluctuations, has remained relatively stable.

An RFP was released this week for a Saturn/Cassini-Huygens updateable planetarium show. Total show length will be approximately 20-30 minutes. The Cassini/Huygens mission seeks proposals for shows serving both the small and rural planetaria community through the mid and upper range community. The initial version of the show is to be ready for release in 2003 and will highlight the launch, cruise flight, flyby of Jupiter, approach to Saturn, and the events that will occur upon arrival at Saturn. A second version is planned to be released in mid-2005.

Outreach staff traveled to Berkeley, California to meet with individuals from the Bay Area Writing Program (BAWP) and project FIRST. This meeting was the first organizational step toward implementation of Cassini's K-4 language and reading program.

Additional information about Cassini-Huygens is online at

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-Huygens 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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