24 Aug 2001
(Source: Jet Propulsion Laboratory)
Cassini Weekly Significant Events for 08/16/01 - 08/22/01
The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, August 22. 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, http://www.jpl.nasa.gov/cassini/english/where/.
Recent spacecraft activities include a Magnetospheric and Plasma Science observation, an Ultraviolet Imaging Spectrometer Interplanetary Hydrogen Survey and Periodic Instrument Maintenance, a Radio and Plasma Wave Science (RPWS) High Frequency Receiver calibration, and an autonomous Solid State Recorder Memory Load partition repair. Real-time commands were uplinked to the spacecraft as planned to transition to the Reaction Wheel Assembly for attitude control and to perform a Command & Data Subsystem Memory Readout of the Non-Interfering Error Log.
Instrument Operations (IO) Radio Science Subsystem conducted a test of the X-band Traveling Wave Tube Amplifier (TWTA) as part of the second Gravitational Wave Experiment System Test, which began this week. The X-band TWTAs were placed in standby mode for 18 hours, then warmed up for 2 hours and turned on again. This was done to obtain thermal information relevant to operations mode development. A similar test was performed the following day with the Ka-Band TWTA, to obtain thermal information that will be useful for tour development.
The Science Planning Team began holding weekly Target Working Team (TWT) meetings to integrate science activities for the entire tour. In addition to the Titan Orbiter Science and Satellite Orbiter Science Teams (TOST and SOST), the four new teams responsible for integrating segments of the tour are the Saturn, Magnetosphere, Rings, and Cross-Discipline TWTs. The TWT meetings are held Monday through Thursday and will continue for the next three years or until the tour has been completely integrated. Additional tour planning took place at an all-day SOST meeting, which was held to continue work on integrating the targeted icy satellite flybys.
The Spacecraft Operations Office (SCO) held the third in a series of Maneuver Automation Tool progress briefings. There has been substantial progress and the prototype scripts and block are well along in development. The developer is preparing for formal delivery of the software and documentation in January 2002.
The Navigation team delivered the Cassini orbit determination quarterly update, which covered the data arc from April 2001 to July 2001. The predicted Saturn encounter is several thousand kilometers from the Trajectory Correction Maneuver 17 aimpoint due to normal TCM-17 delivery dispersions and spacecraft thruster activities including the safing event earlier this year. However, this is well within expected trajectory variations at this point in the mission, and will have no noticeable effect on subsequent maneuvers.
The Thermal Devices team has completed the analysis of the Reaction Control System catalyst bed heater tests performed in cruise sequence C26. The results of both tests were normal and validate the 32-minute warm-up time and the thermal stability of having both branches powered simultaneously.
The Uplink Operations office completed system testing for Mission Sequence Subsystem (MSS) D7.6, including Integration Test Laboratory and High Speed Simulator retest of modules for MSS D7.6. The integrated retest was completed last weekend, and the MSS D7.6 Delivery Coordination Meeting took place this week. The new delivery includes significant updates to Science Opportunity Analyzer, Pointing Design Tool, and the MSS modules, both ground-expanded and on-board.
IO installed and performed initial testing of a new Remote Terminal Interface Unit (RTIU) for the RPWS team. Testing of the RTIU was successful with individual commands, and further work and testing is planned for more complex commanding.
The Mission Planning (MP) team held a review of Saturn Orbit Insertion planning status. Discussion included the recommendation to use the High Gain Antenna (HGA) to protect the spacecraft during ring plane crossings. The group decided to hold a half-day debris hazard review in conjunction with the upcoming October Project Science Group meeting. MP also received reports from main-engine nozzle testing at White Sands Test Facility, and negotiated with propulsion experts for a September reassessment of Cassini nozzle vulnerability.
Mission Assurance completed generation of a Mission Operations Assurance Plan (MOAP) for the program. This plan documents the Operations Assurance effort for Cassini and relies heavily on the synergistic relationship between Mission Assurance and Systems Engineering. Detailed role statements for both Mission Assurance and Systems Engineering are provided, with traceability to both the Mars Climate Orbiter Failure Review Board recommendations and the JPL Design Principles. The MOAP is currently being tailored by Cassini Systems Engineering and should be released to the Flight Team within a few weeks for review.
Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Cassini mission for NASA's Office of Space Science, Washington, D.C.
Cassini Mission to Saturn and Titan
Jet Propulsion Laboratory
California Institute of Technology
National Aeronautics and Space Administration