Cassini Significant Event Report

For Week Ending 07/12/02

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Tuesday, July 9. 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.

Instrument activities at the conclusion of the C32 sequence included maintenance of the Magnetospheric Imaging Instrument Low Energy Magnetospheric Measurement subsystem motor, power off of the Imaging Science Subsystem (ISS) Narrow Angle Camera replacement heater to lower temperatures for C33 imaging activities, and the conclusion of the Solar Conjunction Experiment. Spacecraft activities included a Reaction Wheel Assembly unload and a return to thruster control, clearing of the high water marks, and an AACS periodic engineering maintenance containing a main engine gimbal actuator exercise, Backup Assisted Load Format Injection Loader maintenance, and backup reaction wheel exercise.

C32 was the last sequence of Cassini's cruise subphase. C33, the first sequence in the Space Science Subphase, was uplinked and began execution this week. Initial instrument activities included a Radio and Plasma Wave Science high frequency receiver calibration, an ISS dark frame observation and a Spica observation to support haze
anomaly resolution, and a Cosmic Dust Analyzer test of a new housekeeping data type. Spacecraft activities included transition to reaction wheel control, clearing of the AACS high water marks, and an autonomous Solid State Recorder memory load partition repair.

Radio Science data acquisition for the Solar Conjunction Experiment ended July 5, completing the month-long experiment. During this time the Radio Science Team and Mission Support and Services Office personnel provided round the clock support. About 24 megabytes of data were collected, with about 90 percent being open-loop data and the other 10 percent being closed-loop data. Data analysis has begun.

The official end of Superior Conjunction occurred when the Sun - Earth - Probe angle reached 15 degrees. The Spacecraft Office reported reaction wheel predictions for the 30-day conjunction period were met as expected, and that no desaturations were required. Command testing was performed during the week surrounding minimum separation. Results were found to be similar to the previous 2 conjunction periods. Commanding is unaffected down to about 2 degrees Sun-Earth-Probe angle, then drops to about a 10% command acceptance rate at 1 degree separation.

The Huygens Probe team has finalized the sequence for Probe Checkout #10 and delivered it to the Sequence Virtual Team.

ISS completed the final report for the decontamination activities performed in C32.

SCO distributed a draft version of Probe Relay Critical Sequence Document to the Probe Mission Review Team.

The kickoff meeting was held for the second Tour Science Planning Virtual Team process. Under development are Science Operation Plans for S11 and S12, covering orbits 8 through 12. This process will complete in October of this year.

Status presented at last week's Project Science Group meeting held in Lisbon, Portugal included Cassini Program, Huygens Probe, Science Planning, and archiving reports. Each of the Target Working Teams, science teams and Discipline Working Groups also presented status reports. Discussions were held on options for communications with
Earth during Saturn Orbit Insertion.

Topics at this week's Mission Planning Forum included a status report on rolling downlinks and rocking downlinks, an update on results of ranging on/off for 70m stations and arrays, and the orbiter activity plan during the Huygens mission. Discussion included restrictions on orbiter science activities. The orbiter activity plan will be presented at next week's Probe Relay Design and Risk Review.

Uplink Operations Team members traveled to the University of Michigan to perform training classes on the Pointing Design Tool for Cassini Plasma Spectrometer and Ion and Neutral Mass Spectrometer instrument team members.

Mission Assurance has developed a set of metrics for risk management status reporting. A task plan has been negotiated with Raytheon, to implement the metrics in the on-line Risk Management Tool along with the capability to download the risk management database into an excel spreadsheet. The metrics will provide an illustration of the aggregate project risk exposure, over time and by mission phase.

Cassini Education Outreach has taken delivery of the final version of each of 20 educator briefs that form the basis for the "Saturn In Your Kitchen and Backyard" series. Each activity is inquiry based, hands-on, and is aligned with national science education standards. The educator briefs will be available through the education section of the Cassini web site.

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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