Cassini Significant Event Report
For Week Ending 04/11/03

The most recent spacecraft telemetry was acquired from the Canberra tracking station on Wednesday, April 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.

Command and Data Subsystem (CDS) Flight Software (FSW) checkout activities continued this week with an Instrument Expanded Block (IEB) load to the SSR library region. This procedure uplinks and stores IEBs in the new Version 9.0 Library region. The Library Region is a new sub-partition on the SSR that allows instruments or subsystems to store frequently used commands on the SSR for an extended length of time. When needed, a single command will load this data from the Library region to the instrument for execution. This procedure loaded and verified that Instrument IEBs were loaded into the Library region successfully.

After the IEB load, the CDS Command Loss Timer threshold value was set to 2 days, and a High Gain Antenna (HGA) response checkout was performed. The purpose of this procedure was to demonstrate that the new System Fault Protection algorithm called the HGA Response will change the uplink data rate to 250 bps, and the downlink telemetry mode to RTE-1896, as well as the proper execution of the 7SAFE,îOTHERî response. This procedure was clean and successful, thanks to all the support from Systems, Attitude Control Subsystem (ACS), System Fault Protection, Telecom and others.

Following the HGA checkout, the ACS High Water Marks were cleared, CDS Background Sequence #2 uplinked, CDS Command Loss Timer threshold returned to the nominal 11 day value, and a Probe Solid State Recorder dual record demo was begun. This will be the first in-flight demonstration of the Probe Relay telemetry mode with dual SSRs.

A simulation procedure review meeting was held for C37 as part of the sequence development process. Testing in the Integrated Test Laboratory for the C37 background sequence and Trajectory Correction Maneuver 19 began this week and continues to the weekend.

A wrap-up meeting was held for Science Operations Plan (SOP) implementation for tour sequences S15/S16. The sequences will now be archived until June of 2005 when SOP Update, and the Science and Sequence Update Process will begin.

The S17/S18 preliminary port#3 inputs have been delivered. A data volume problem occurring on two days was identified, and later resolved at the weekly Tour Process meeting.

The C38 Science Planning Team process kicked off this week. Development of this sequence will use a compressed five week schedule, and completes in early May.

SOP Update Verification and Validation (V&V) using S14 continued this week. Cassini Information Management System (CIMS) change requests were published to identify changes the teams need to make to their CIMS requests. Mission Sequence Subsystem developers provided user support for D9.0 PDT and SEQ_CONVERT during the on-going V&V exercise.

Mission Planning presented the results of the extended mission planning and budget task. Budget and workforce estimates were delivered along with a final implementation schedule.

System Engineering is leading preparation for the Approach Science/Tour Operations Readiness Review to be held in October of this year. A requirements and capabilities table organized by Operations Concept has been generated and is being reviewed by the Teams/Offices.

In last weeks Significant Events report, an incorrect ULR was listed for the Kids' section of the Cassini website. The correct URL is http://saturn.jpl.nasa.gov/kids/index.cfm

University of Hawaii astronomers formally announced the discovery of the first new satellite of Saturn in three years at the International Astronomical Union on April 8, 2003. The satellite has a distant retrograde orbit, and is about 8 km in diameter. For more information go to http://www.ifa.hawaii.edu/~sheppard/satellites/sat2003.html

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-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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