Cassini Significant Event Report

For Week Ending 10/08/04

The most recent spacecraft telemetry was acquired from the Madrid tracking station on Wednesday, October 6. 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 .

This week, the Spacecraft Operations Office performed a checkout of the updated version of the Attitude Control Subsystem (ACS) flight software. ACS version A8.7.1 prepares Cassini for Huygens Probe release on December 24, 2004 and the remainder of tour operations. The checkout was a simulated probe release using the spun-up reaction wheels to impart a torque for the thruster system to respond to. Both ACS computers are now up and running on A8.7.1.

After the checkout was successfully completed, a science mini-sequence was uplinked and began execution to continue S04 on-going observational campaigns. This included movies looking for spoke formations in Saturn's rings, ultraviolet imaging of Saturn's magnetosphere, and solar wind measurements by the Magnetospheric and Plasma Science (MAPS) instruments.

An update to the Cassini reference trajectory was released on Monday, October 4. This reference trajectory, labeled 041001, increases the accuracy with which the Huygens probe will be delivered to Titan, and incorporates updated orbiter and major satellite ephemerides. The major changes from the previous reference trajectory are a decrease in the altitude of the second Titan flyby (Tb) from 2200 km to 1200 km, and an increase in the fourth Titan flyby (T3) from 1000 km to 1577 km. The improved satellite ephemerides resulted in small changes to the timing of events such as Titan flybys and Saturn periapses.

A meeting was hosted by Uplink Operations to discuss the timeline for a one day Live Update for the Iapetus distant flyby during S04. A decision was reached to proceed with implementation of the update.

S05 is currently going through the Science and Sequence Update Process (SSUP) and will be completed on October 15. The release of the new reference trajectory has driven a quick replan of the development schedule and a review of the priorities for the remaining activities. A meeting was held to discuss impacts and required actions as a result of the new trajectory, and minor modifications to the sequence are underway.

The final S05 Ta-Radar test concluded execution in the Integrated Test Laboratory this week. The sequence executed as planned.

A Simulation Coordination meeting for events in S06 was held this week. The main topic of discussion was the simulation of the Tb flyby.

The S07 Science Operations Plan (SOP) Update process completed this week. A hand-off product was delivered to the Sequence Team leads, who then held a kickoff meeting for the SSUP process.

Preliminary port#1 occurred on Monday of this week as part of the S08 SOP Update process. The products were merged and a report was delivered identifying problems and issues that need to be resolved in time for the official port. The official port was shifted by two days to allow the teams more time to update their designs for the new reference trajectory. The waiver request disposition meeting for this process was cancelled as no new waiver requests had been submitted.

The Science Planning leads for the S10 Aftermarket process released a list of events and time shifts as a result of the new reference trajectory. S10 executes in April 2005 and includes the Titan 5 and 6 flybys as well as flybys of Mimas, Teheys, Epimetheus, and Calypso.

The Radio Science Subsystem team has released a report on activities that occurred on September 17, 18, and 24. These included a 3-hour Ultra Stable Oscillator characterization, a 1-hour special High Gain Antenna boresight calibration, Ka-band Translator testing, monopulse and blind pointing testing, and a Bay-7 warm-up/thermal stabilization test. These events occurred over Madrid's DSS-63 and DSS-55 stations. In addition, engineering passes were scheduled over Goldstone's DSS-25 and DSS-26 stations for the purpose of verifying the monopulse tracking system and the antenna blind pointing.

A program internal Tour Science Talk was given this week on the topic of recent Magnetometer Subsystem and Cosmic Dust Analyzer science results.

Delivery Coordination meetings were held for Cassini Operations Reference Encyclopedia (CORE) V5.0 and Mission Sequence Subsystem (MSS) version D10.3.3. Cassini Archive Tracking System (CATS) v2.0 and CORE v5.0 were successfully installed on the operations network this past Monday.

The Mission Support & Services Office reported that in the period between September 28 and October 3, Cassini received the support of 7 DSN passes, and uplinked 32 command files to the spacecraft.

Mission Assurance convened a Risk Team meeting this week to reassess risks identified for Probe Release and Probe Relay. Four new risks were identified following the previous meeting and they were added to the list for evaluation this week. There are currently 27 Probe risks identified in the Significant Risk List. Results of the latest risk assessment will be presented at the Probe Mission Critical Event Readiness Review later in October.

Cassini Science Planning and Outreach team members attended the 32nd annual International Storytelling Festival in Jonesborough, Tennessee this week. The Library of Congress collected and videotaped true stories of American Space Exploration from Cassini and Mars mission scientists and engineers during the festival. Cassini images of Saturn were displayed in an exhibit in the Storytelling Parlor, while Cassini staffers answered questions from some of the 12,000 festival attendees.

Cassini Outreach and Science team members are participating in the NASA Explorer Institute for national trainers from Girl Scouts of America this week at JPL. During the evening NASA Resource Night at Mt. Wilson Observatory in Pasadena, CA, Cassini Outreach discussed how the Saturn Observation Campaign members around the country ( could be tapped for Girl Scout events. During the science-engineer career interviews and lunch with Girl Scouts, several Cassini team members volunteered as interviewees and lunch mates.

A series of Cassini stories is being presented on StarDate, a radio program and Internet resource based at the University of Texas McDonald Observatory. Each month, StarDate offers a balance of astronomy and space science topics. There are 36 stories on Cassini, going back to July 2000.

For the most recent Cassini information, press releases, and images, go to