Cassini In Fine Shapes As Spacecraft Checkouts Continue

RINGWORLDS

just a little further and Cassini will fire up for 90 minutes of nail biting anticipation as NASA enters orbit about Saturn for the first time.

Pasadena - Aug 11, 2003
The most recent spacecraft telemetry was acquired from the Madrid tracking station on Wednesday, August 6. The Cassini spacecraft is in an excellent state of health and is operating normally. On board activities this week included the conclusion of the Saturn Orbit Insertion (SOI) demonstration, conclusion of the command moratorium period, playback of SOI demo data, uplink and execution of nominal post SOI demo clean up commands, and instrument reconfiguration following the demo.

The SOI critical sequence demonstration was an end to end demonstration of the spacecraft preparation, the eight-day critical sequence, and the clean-up activities to be performed in June and July of 2004.

The preparations and clean-up activities included both sequenced, and real-time commands as they are planned for execution in 2004. The sequence itself was stripped of the main engine firing commands, and other commands with potentially irreversible effects, and replaced with "NO OP" commands to make the sequence size match exactly.

The Spacecraft Operations Office (SCO) considered this activity to be the final verification of the critical sequence capabilities in the Attitude Control (AACS), and Command and Data System (CDS) flight software versions uplinked earlier this year.

The final capability to be exercised is the accumulated energy cutoff logic for maneuvers. That demonstration will be part of Trajectory Correction Maneuver 19B scheduled for October 2003.

During the final hours of the SOI Demo, the Radios Science Team used the Radio Science Subsystem (RSS) open loop receiver to track the low gain antenna (LGA) X-Band signal.

Using RSS tools, real-time visibility was afforded the project to confirm the presence of the signal following each of the spacecraft turns, progress during the burn, and was used to verify the last "call home" signal. For SOI, this Radio Science instrument will become the prime tool for real-time visibility into the progression of the SOI maneuver.

C39 sequence generation concluded this week with participating instruments delivering final instrument expanded block (IEB) files, release and review of the Final Sequence Integration and Validation (FSIV) products, and uplink approval given for the sequence at the FSIV approval meeting.

IEBs for Cassini Plasma Spectrometer, Ultraviolet Imaging Spectrograph, and Radio and Plasma Wave Science have been uplinked for this sequence. The background sequence itself will be uplinked to the spacecraft next week.

Saturday was the last of the post Solar Conjunction Experiment (SCE)#2 DSS-25 passes that the Radio Science Systems Group has utilized to characterize the Ka-band Translator (KaT) anomaly. Problems with the Ka-band transmitter at DSS-25 prevented successful execution the planned tests.

As of last Saturday, the KaT was still in the bad region. The next scheduled opportunity to attempt KaT recovery begins in mid September during the RSS Engineering Tests, and quiet test. In the meantime, the Radio Science team will be evaluating information known to date in consultation with the KaT manufacturer.

System engineering conducted a wrap up meeting this week for the S14 Science and Sequence Update Process (SSUP) Verification and Validation (V&V) activity. Topics included a general review and summary of activities, V&V assumptions and liens, review of some of the open issues, and discussion of tasks remaining to be performed.

Pointing Design Tool (PDT) developers from the Uplink Operations team presented a training session on the D9.1 version of PDT.

Mission Assurance convened the quarterly Risk Team Meeting to address cruise risks this week. Risks were reviewed and re-assessed for changes to likelihood, impact, or mitigation efforts. The team also discussed future retirement dates for cruise risks. Those cruise risks which do not apply to Saturn Tour Operations will be retired after SOI next year.

The application window for new Saturn Observation Campaign members closes 29 August 2003. 51 new applicants were accepted into the program during July, bringing the total number of amateur astronomers in the program to 149.

The Outreach Team attended a workshop on educational techniques for special needs students at Goddard Space Flight Center. The South East Regional Clearinghouse (SERCH) hosted the event. SERCH is a NASA broker and facilitator that provides support in all space science research areas, "plays matchmaker" between scientists and Education/Public Outreach programs, and assists in regional distribution of educational products. At the workshop, Cassini outreach personnel presented a mission overview and introduced different Cassini education materials.

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Mission to Saturn

Sydney - Apr 03, 2003
For the past few years SpaceDaily has published a series of detailed articles on the upcoming mission to Saturn which will get underway later this year as NASA's Cassini spacecraft approaches Saturn ahead of a 90 minute engine burn to place the billion dollar spacecraft in orbit about Saturn.

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