Cassini Significant Event Report

For Week Ending 06/07/02

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, June 5. 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.

Instrument activities this week included uplink of Imaging Science Subsystem (ISS) Flight Software (FSW) version 1.3. Memory Readouts verified a complete and successful load. ISS also performed a FSW checkout, along with decontamination diagnostic imaging. Results of both activities will be available next week.

Radio Science begins the Solar Conjunction Experiment (SCE)#1 this week. The SCE, a 30-day experiment, aims to measure a peculiar effect of solar gravity on the trajectory of electromagnetic radiation. In particular, the photons are deflected and delayed by the sun. Einstein predicted this effect in 1916 and its measurement during a solar eclipse in 1919 was the first experimental test of General Relativity. Alternative theories of gravity allow for different and adjustable values of the solar gravitational deflection. With this experiment, General Relativity could be tested at a level of 1 part in 100,000, one hundred times better than past experiments, dating
back to 1978.

Additional instrument activities included the uplink and activation of two Radio and Plasma Wave Science (RPWS) PRIMO looper programs to update RPWS data collection rates during the SCE, ISS observations of Spica, Visual and Infrared Mapping Spectrometer occultation and alignment test activities at Spica, and an Ultraviolet Imaging Spectrograph Spica calibration.

Spacecraft activities this week included a transition to Reaction Wheel Assembly (RWA) control for Spica observations and the SCE, an RWA momentum unload, uplink of an AACS/ Radio Science Subsystem Ka-band & X-band body vector update Immediate/Delayed Action Program (IDAP), uplink of an AACS RWA counter reset IDAP to zero out all RWA revolution counters in preparation for the SCE, and a clearing of the AACS High Water Marks.

As reported last week, the Composite Infrared Spectrometer (CIRS) executed a mute/unmute test in support of probe checkout activities. The spacecraft successfully muted and unmuted CIRS. Bus traffic ceased as expected and the command to unmute executed. CIRS however did not successfully send data to CDS after the execution of the unmute command. The instrument was then power-cycled in the background sequence as planned and communication between CDS and CIRS resumed. Investigation by the CIRS team is underway.

The Titan Orbiter Science Team (TOST) held a meeting to integrate the period around +/- 1 day for the Titan-23 through Titan-32 flybys. TOST developed a reusable template to integrate these flybys, significantly reducing the workload associated with developing these and future integrated plans.

Radio Science (RSS) held a System Assessment Meeting for Solar Conjunction Experiment #1. The Deep Space Network (DSN), Telemetry, Tracking, Command & Data Management (TTC&DM), Spacecraft Operations Office, Uplink Operations, and RSS all reported readiness to conduct the experiment. Mission Support & Services Office and RSS will be staffing all DSN tracks. The experiment will have 24-hour coverage 7 days a week.

The C34 science planning process kicked off this week with Mission Planning personnel assisting.

The primary topic at this week's Mission Planning Forum was exploration of the idea of Mission Planning assuming responsibility for coordinating all Cassini DSN passes during tour. The discussion covered the cons of Science Planning (SP) having to request changes through a layer of bureaucracy vs. the pro of Mission Planning's possible ability to negotiate neutrally between SP and the various teams in the Spacecraft Office, and apply consistent, complete guidelines on all passes. The idea is to avoid some of the problems encountered during the S9 & S10 Science Operations Plan implementation activity.

Mission Assurance participated in a joint workshop between JPL and the Aerospace Corporation, to discuss Risk Management. The Cassini risk management process used during Mission Operations & Data Analysis was presented and was well received by the audience. Four different tools were also demonstrated including the Cassini Tailored Risk Management Tool that is developed and managed by Raytheon. Objectives of this workshop included teaming to best evolve the practice of Risk Management and a desire to develop consistency between the two organizations.

This week Cassini Outreach formally announced the "Saturn Observation Campaign". This program seeks amateur astronomers to serve as local "Saturn observation experts" in their communities. Details of the program as well as the opportunity to participate can be found on the Cassini web site at

Additional information about Cassini-Huygens is online at

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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