Cassini Significant Event Report

For Week Ending 05/24/02

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, May 22. 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.

Commands for the Cosmic Dust Analyzer were uplinked to reset the ion grid voltage to nominal levels, set the event definitions back to "on", and send test pulses to verify instrument status. This activity completed nominally with expected results.

Additional on-board activities included uplink of the ACS high water mark clear using the new command system, and new V26.4.1 command view utility. The nominal real-time command process was followed allowing the Sequence Team lead to identify necessary updates to existing procedures for use with the new command system.

The Cassini Spacecraft Office held a one day Probe Relay Critical Sequence Design Review. The meeting was attended by personnel from the Cassini offices, and several members of the Huygens Probe Team. No major issues were raised. Both Cassini and Huygens teams were satisfied with the present sequence design, which will soon be placed under configuration control.

Visual and Infrared Mapping Spectrometer (VIMS) C32 data is being analyzed to determine why it was affected by data policing. Ground algorithms for estimating required data volumes might need to be adjusted. Composite Infrared Spectrometer personnel have received all the data from a boresight calibration executed earlier in the month. The next few weeks will be spent in analyzing the data.

VIMS team members based at JPL traveled to the University of Arizona to discuss tour process coordination with the VIMS team. The split of tour responsibilities between Instrument Operations at JPL and the University of Arizona was the primary topic of discussion. Other topics included what information is needed in the various phases of tour planning, the timing and coordination of that information delivery, update of the observation description Software Interface Specification for tour, status of the VIMS planning database, status of Instrument Operations (IO) validation software, and engineering/science/calibration plans for the remainder of cruise.

A Critical Design Review was held of system level verification and validation plans for the Cassini Operations System for the tour phase. The review was very successful and focused on plans, priorities, and risk analyses. The review board found that the plans were comprehensive and represented a good balance between resources and acceptable risk.

Revision N of the Mission plan, and Mission Plan quick reference guide were released and distributed this week. Mission Planning also hosted a C34 scoping meeting to discuss activities to be included in that sequence.

Imaging Science Subsystem Flight Software version 1.3.0 was approved for uplink at a Delivery Coordination Meeting Software Review Certification Requirement review in mid April pending the closure of a few testing liens. Those items have now been closed and the software is approved for uplink in C32.

Due to unexpected interactions between the Cassini ground system environment and the new core functionality of the Science Opportunity Analyzer (SOA), it has been decided to drop SOA from the next delivery of Mission Sequence Subsystem software version D8.0.1 A meeting will be held next week to assess progress on resolving the issues, and set a new delivery date for SOA. Indications are that the slip is on the order of a month, and would be designated D8.0.2. Other contents of D8.0.1 are not affected.

ULO has hosted two Cassini Information Management System (CIMS) planning meetings with representatives from System Engineering, Science Planning, Uplink Operations, and CIMS development attending. The meetings have focused on how to better involve all CIMS users in the process of prioritizing future CIMS developmental items.

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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