2 Nov 2001
(Source: Jet Propulsion Laboratory)
Cassini Weekly Significant Events for 10/25/01 - 10/31/01
The most recent spacecraft telemetry was acquired from the Canberra tracking station on Wednesday, October 31. 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 instrument activities include a Radio and Plasma Wave Science (RPWS) High Frequency Receiver calibration, a Composite Infrared Spectrometer boresight calibration, and an Ultraviolet Imaging Spectrograph (UVIS) Interplanetary Hydrogen Survey and Spica observation. Engineering activities taking place onboard the spacecraft this week include a static phase error test to characterize the spacecraft Deep Space Transponder uplink receiver tracking, and the final S-band pattern calibration for the Huygens Probe radio system. A minisequence uplinked last week executed and overlaid the Attitude Control Subsystem (ACS) momentum bias commands from the background sequence with new updated values produced by the ACS team.
In preparation for the upcoming 40-day Gravitational Wave Experiment, the Radio Science Subsystem (RSS) team conducted a dataflow test in order to verify data paths in the RSS Ground Data System. DSN station personnel were familiarized with the monopulse system configuration, calibration, and operation, and flowed the monopulse monitor data back to JPL. RSS also conducted a long Ka-2-band track, with the various subsystems performing extremely well. Other activities performed in preparation for the GWE include an Ultra-Stable Oscillator characterization, a boresight calibration, and an RSS quiet test with the Fields, Particles, and Waves (FPW) instruments to determine if the RSS can detect the FPW instruments in their "noisy" states.
The Imaging Science Subsystem (ISS) post-warm-up images were downlinked for analysis. The 15 images were planned in support of the UVIS Spica observation, and were examined for potential changes relative to the pre-warm-up images. Preliminary results show a change in the character of the anomaly with the halo gone but more spreading of the star image than before. ISS also performed a scattered light observation, in an effort to resolve an anomaly observed in C25 when an ISS observation received far more light than expected. This current observation included a series of scans across the sky to see how much scattered light ISS gets at different distances from the sun for a selection of different orientations, to see if reflection off another part of the spacecraft is causing the extra light seen by ISS.
The RADAR team performed an instrument calibration, which involved collecting radiometry data of two microwave sources while executing repeated box scans. These scans were performed as close as possible to the power-on of the instrument so the RADAR team can better characterize their warm-up calibration requirements. Currently, RADAR is requiring 3 hours of warm-up for radiometry in science planning, which causes them to frequently conflict with other instrument teams. They are hoping to be able to reduce their warm-up time based upon the understanding they receive from analyzing this data.
In conjunction with the ISS scattered light observation, the Magnetospheric Imaging Instrument (MIMI) performed a test of the Ion and Neutral Camera (INCA) collimator. The test ramps the INCA high voltage collimator plates up to operational voltage on the positive plate, leaving the negative turned off. This is done in coordination with the scattered light test to provide a condition of sunlight on the collimator plates, but no thruster activity. It tests the theory that this configuration will prove to be noise-free for RPWS and Cassini Plasma Spectrometer (CAPS). RPWS supported this test by monitoring its data for interference.
The C29 Sequence Team development phase has been completed. The Final Sequence Integration & Validation Approval meeting was held, and all Cassini teams approved the sequence for uplink. The C29 sequence will be uplinked on Nov. 1 and will begin execution on Nov. 4. This sequence includes a Visual and Infrared Mapping Spectrometer radiator test, a 5-pass Probe Relay Test, the first of three GWEs, an Attitude Control Subsystem (ACS) Periodic Instrument Maintenance, and a Cosmic Dust Analyzer flight software upload and checkout.
The Science Uplink Verification (SUPV) activity for three Titan flybys has been completed, and the SUPV for three Icy Satellite flybys begun. The Science Planning Team is in the process of generating a final report on the Titan SUPV, which will include lessons learned from this exercise. A full suite of Target Working Team (TWT) integration team meetings was held last week to continue with the integration of the tour. Semi-monthly Satellite and Titan Orbiter Science Team meetings are now being held on Fridays.
The Attitude Control Team has released its the third quarter report. In summary, the attitude control system is operating properly. There were no fault protection entries, all trends are as expected, and all scheduled activities were executed normally.
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 Outreach Cassini Mission to Saturn and Titan Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration