Cassini Significant Event Report

For Week Ending 04/12/02

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, April 10. 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 this week included periodic instrument maintenance for the Radio and Plasma Wave Science subsystem, and an Ultraviolet Imaging Spectrograph Hydrogen Deuterium Absorption Cell conditioning exercise. The purpose of conditioning is to regularly exercise the H and D cell filaments. Additional spacecraft activities included clearing of the ACS high water marks, and an ACS periodic engineering maintenance (PEM). The PEM contains the main engine gimbal actuator exercise, Backup ALF Injection Loader maintenance, and backup reaction wheel exercise. Results of the PEM were as expected.

The first Science Planning Team input port for C33 occurred this week. Process output files will now be merged and delivered to ACS for pointing validation runs.

A Saturn Orbit Insertion (SOI) Target Working Team met for the first time this week. Integration work has begun on the period immediately following SOI. A Science Operations Plan (SOP) implementation Tiger Team met to explore an alternate approach of developing four tour sequences in two Science Planning Team processes. Some issues were identified and will be worked over the next couple of weeks. In general, this approach was agreed to be a good option since it reduces the number of processes and overhead associated with implementing the SOP.

The Spacecraft Office held a maneuver wrap-up meeting after Trajectory Correction Maneuver (TCM) 18. At this meeting it was confirmed that the TCM performance was nominal. The team reviewed the new tour processes that were used in the design of this TCM to identify desired improvements or lessons learned.

A Flight Software Monthly Management Review was held this week. Development progress for Saturn Orbit Insertion, Huygens Probe Relay, ACS flight software, and CDS flight software were reviewed. All items are proceeding as scheduled.

Uplink Operations personnel made a presentation to Program Management for performing a tour Science and Sequence Uplink Process (SSUP) Verification and Validation (V&V) activity in mid 2003. A series of smaller pre-tests and demonstrations was proposed, culminating in a full-up SSUP demonstration mid-year.

To make the needed personnel available, the proposal included plans to create a minimal set of activities in C38, moving most of them into C37 and C39. V&V would then be performed during the C38 development/execution period. Program Management approved the plan, and directed the team to proceedas proposed.

All of the planned Mission Sequence Subsystem D8 deliverable applications are in hard-freeze and system testing is proceeding as planned. May 8, 2002, is still a firm date for the delivery to support the May 13, 2002, start of Science Operations Plan integration.

User acceptance testing for the Cassini adaptation of the Command System Version 26.4 was completed this week. An in-flight demonstration was also performed. Additional demonstrations have been scheduled for mid April and early June.

A scale model of the Huygens Probe is now on loan to the Space Center Museum in Houston, Texas. The model will be part of a summer exhibition and will be returned to the Space Flight Operations Facility at JPL for display in September.

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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