Cassini Significant Event Report

For Week Ending 06/21/02

Cassini is currently maintaining 24-hour Deep Space Network coverage in support of the Radio Science Solar Conjunction Experiment. The most recent spacecraft telemetry confirms 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.

On-board activities this week included uplink of the High Water Mark clear, and the first conjunction test commands. When the separation angle reached about 3 degrees, the project began uplinking a command file consisting of 10 no-op commands sent every 5 minutes. The file is uplinked 10 times daily. These commands have been sent to the spacecraft each time Cassini enters Solar Conjunction. The previous occasion was in June of 2001 and the next opportunity will be July of 2003. The purpose of the test is to accumulate statistics for uplink reliability at decreased separation angles. Saturn Orbit Insertion will occur on July 1, 2004 and conjunction will follow within 7 days. Knowledge of how conjunction affects commanding will be crucial at that time.

The Radio Science Subsystem Solar Conjunction Experiment continued this week. The Ka-band transmitter at DSS-25 tripped due to a heater exchanger problem. Facilities and maintenance engineers have been working to correct the problem but have been unable to bring the transmitter back on-line. The minimum separation angle occurs on Friday June 21.

C33 is currently in the preliminary Sequence Integration and Validation Phase. This week a meeting was held with the Spacecraft Office (SCO) and interested instruments to discuss a SCO request to include an in-flight gyro calibration of scale factor, misalignment, and biases to correct an error in flight software. SCO needs to perform the calibration prior to C36 so updates may be included in the next software build. The test has been tentatively scheduled for mid July pending resolution of a number of action items.

Program Management approved Mission and Science Planning's design for the C34 sequence at a Project Briefing held this week. C34 will observe 30 targets, execute a Probe receiver test, and perform a compatibility test for a new ESA tracking station at New Norcia, Australia. C34 provides an opportunity for a loading test of the flight team's ability to manage an increased number of targets. It was observed at the briefing that the number of activities planned in C34 is at least twice that of previous cruise sequences, and emulates a modest plan for a tour sequence.

The first input port occurred this week for the Science Operating Plan integration of tour sequences S9 and S10. The files have been delivered to AACS for processing.

A Target Working Team / Orbiter Science Team process improvement meeting was held by Science Planning (SP). The meeting went well. Participants felt that in general the process is working well and that only a few areas needed to be targeted for improvement.

All teams and offices supported the Cassini Monthly Management review. A new Cassini Science and Uplink Office Manager has been appointed. Transition plans are still to be developed.

System Engineering (SE) began assisting teams in bringing training plans and schedules up to date to support Verification and Validation activities, and V&V, Approach Science, and Tour operations readiness reviews. Initial activities included meeting with Uplink Operations Personnel to identify training needs and document training plan guidelines. The guidelines will be presented to the Program next week.

Outreach personnel attended the NASA OSS Conference in Chicago, Illinois.

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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