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Significant Event Report for Week Ending 1/24/2003

Cassini Significant Event Report

For Week Ending 01/24/03

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, January 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.

On-board activities this week included clearing of the ACS high water marks, a Reaction Wheel Assembly mode transition to support Cassini Plasma Spectrometer (CAPS), Visual and Infrared Mapping Spectrometer (VIMS) and RADAR activities, Radio and Plasma Wave (RPWS) High Frequency Receiver calibrations, uplink and execution of the VIMS flight software V6.1 checkout mini-sequence, CAPS Calibration activities, VIMS / Imaging Science Subsystem (ISS) observations of Gamma Crux and Alpha Taurus, RADAR radiometric calibrations, a Radio Science Subsystem (RSS) Ultra Stable Oscillator characterization, RSS Periodic Instrument Maintenance and high gain antenna boresight calibration, Ultraviolet Imaging Spectrograph bright body observations of Orion's beta, gamma, zeta and kappa, and a VIMS observation of Fomalhaut.

The observations of Alpha Taurus, Gamma Crux, Fomaulhaut, and Orion's Beta, Gamma, Zeta, and Kappa consist of 18 ISS Narrow Angle Camera images, 48 Wide Angle Camera images, and 96 image cubes collected using the version 5.1 VIMS flight software. All data was processed by the Multimission Image Processing Laboratory.

During the DOY 019 DSS-45 track, sixteen Magnetospheric Imaging Instrument (MIMI) channels went into alarm. It was determined that the MIMI CPU had halted because of a stack overflow. A real-time command was uplinked to reload the flight software and perform a memory readout of the crashed RAM. The Low Energy Magnetospheric Measurement Subsystem replacement heater was also powered on as a precaution. MIMI has elected to remain in this thermally safe state until it is powered off before the start of C36.

Cosmic Dust Analyzer personnel have detected dust in the region between Jupiter and Saturn. Although the rate is very low (about 1/month), this measurement is the first highly reliable dust impact detection at such distances from Sun. The clear impact signals are very similar to ground based measurements and therefore are believed to be 100% reliable. The last impact occurred on Jan 09, 2003 at 8.0 Astronomical Units. The relative impact speeds of the particles are 50 km/s or higher and their sizes are below 0.1 microns.

A wrap up meeting was held this week for completion of the Science Operations Plan (SOP) implementation activity for tour sequences S13 and S14. The products have been archived and will be revisited in April of 2005 when they begin the SOP Update process.

A kick-off meeting was held this week for Science Operations Plan development for tour sequences S17 and S18.

The Attitude Control (ACS) Flight Software Team held a successful Software Requirements and Certification Review for version A8 of the ACS flight software. This final delivery is a major milestone in ACS Flight Software Development. A8 will provide all the capabilities required for orbital tour operations as well as the Saturn Orbit Insertion and Probe Relay . The Flight Team will uplink and checkout the software on the spacecraft beginning in February.

The Command and Data Subsystem Team completed the first phase of the end-to-end system mode test of their procedures for the uplink and checkout of the Version 9 software. A support equipment problem precluded the telemetry mode test over the three-day weekend. Up to that point, all testing was completed successfully. Testing will resume on February 3.

Over the last several months Instrument Operations (IO) personnel have been involved in the installation of new Remote Terminal Interface Units (RTIU). These units have an important new feature. They can replay a test exactly as run in the Integrated Test Laboratory (ITL) directly from the RTIU to the instrument Engineering Model without involving ITL. This can be done for any instrument, regardless of whether that instrument's engineering model was connected to ITL at the time the test was run. It also removes an enormous load from the always-full ITL schedule. IO is currently making use of this feature to help diagnose a recent ITL test of VIMS that did not perform as expected. This RTIU feature will let VIMS rerun the ITL test whenever and however many times they wish without scheduling any more time in ITL.

Science Planning presented a revision to the tour Science Operations Plan Update process at the Cassini Design Team meeting.

Additional information about Cassini-Huygens is online at http://saturn.jpl.nasa.gov.

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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