Cassini Significant Event Report

For Week Ending 05/14/04

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, May 12. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" web page located at .

The final sequence approval meeting was held this week for S01, the first tour sequence. The background sequence, Ion and Neutral Mass Spectrometer (INMS) mini-sequence, and instrument expanded block loads have been processed and radiated to the spacecraft. The sequence will begin execution on Friday May 14.

Final activities in C44, the last Approach Science sequence, included uplink and execution of commands to reset the Imaging Science Subsystem (ISS) narrow and wide-angle cameras, uplink of Reaction Wheel Assembly (RWA) bias commands to execute in S01, and continuation of C44 science data collection activities.

Sequence development of S02 continued this week with release for review of the S02 Preliminary Sequence Integration and Validation 1 (PSIV) background sequence products, and Sequence of Events /Space Flight Operations Schedule products with a Saturn Orbit Insertion (SOI) burn sequence merged in for reference.

The Spacecraft Team completed a second Operational Readiness Test (ORT) on Saturday, May 9, 2004. This ORT involved Spacecraft Operations, Navigation, and Uplink Operations (ULO). The goal of the test was to demonstrate that these teams could recover from an anomalous SOI and perform a large correction maneuver in less than 3 days. The Navigation analysts were given simulated SOI Doppler data and the Spacecraft team was given an interrupted burn with an underperforming engine. Both teams, with ULO support, were able to diagnose the faults in a timely manner and complete the required work to get to the nominal Orbit Trim Maneuver 1 time.

Three SOI Critical Sequence regression tests were performed on May 10-12, 2004. These regression tests were to ensure that the Critical Sequence would work correctly with the two new ACS mask commands. The mask commands are the response to an ACS fault protection issue that surfaced last month. All tests were successful.

The ACS team completed end-to-end pointing analysis for tour sequences S27 and S28 as part of the Science Operations Plan Implementation process. Preliminary port 1 occurred for S29 and S30. The products have been merged, checked, and reports issued to the teams.

A Project Briefing and Waiver Request Disposition Meeting was held for S03. All waiver requests were approved. The handoff product has been given to the Sequence Team for the start of the SSUP process on May 17.

The S05 aftermarket process began this week with an assessment meeting to discuss proposed changes to the integrated plan. The integration teams will be evaluating these requests over the next couple of weeks, but initially it appears that requested changes fit within available resources. A final decision meeting to disposition the requested changes will be held on May 26.

The total number of ISS images acquired since the start of Approach Science is now 5855, and the number of Visual and Infrared Mapping Spectrometer (VIMS) cubes is 781.

Two items were approved this week in an effort to alleviate downstream workload and increase performance. A request for an update to the Multi Mission Image Processing Laboratory uplink software is now accepted as it will assist in reducing workload downstream on ULO, and after evaluation of Pointing Design Tool (PDT) performance testing, approval was given to release client-server versions of PDT for Mac and Linux platforms.

Instrument Operations, Science Planning, the Spacecraft Operations Office, and the Mission Support and Services Office participated in a Saturn Orbit Insertion (SOI) Playback Assessment Test. The rehearsal was intended to exercise end-to-end SOI Ground System procedures. Data loading into the TDS was expedited, to reflect planned SOI operations, making bested data available to instrument teams within 45 minutes versus 4 hours during normal operations. Team instrument data accountability reconciled with SCO Telemetry Input Gap Analyzer & Reporter data accountability and the teams showed they can easily meet their post SOI 20 hr deadline to evaluate the release of the SSR.

A delivery coordination meeting (DCM) was held for the ISS Pointing Tool (ISSPT) V2.5. ISSPT is a program that allows the user to design imaging observations using the Imaging Science Sub-system on the Cassini spacecraft. ISSPT allows the user to adjust and optimize camera settings, calculate image brightness and content based on pointing, and produce an Instrument Operations Interface output file suitable for building camera command sequences.

DCMs were held for PGT V9.1 and Mission Sequence Subsystem D10.3.1.

The Cassini Literacy Team hosted a booth at the International Reading Association convention in Reno, Nevada. Interest in "Reading, Writing, and Rings" was very high among the teachers in attendance. In addition, several publishers spoke with the team about Cassini products and incorporating Cassini images and products in upcoming publications.

A Saturn Observation Campaign member demonstrated the "What Is Synchronous Rotation?" activity and answered Cassini and Saturn related questions at Space Day 2004. The event, held at the Udvar Hazy Aerospace Wing of the Smithsonian Institution's National Air and Space Museum was part of the nationwide Space Day event.

Recent images of Titan returned by the Cassini spacecraft may be seen at

In an article in the Honolulu Advisor on May 7, it was reported that astronomers using Near Infrared Imager of the Gemini North Telescope on Mauna Kea have observed 10 objects circling Jupiter and four others circling Saturn providing evidence suggesting that clusters of satellites circling Jupiter and Saturn may be pieces of asteroid-like objects that were shattered in collisions early in the existence of the solar system. For more information go to:

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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