Cassini Significant Event Report

For Week Ending 05/02/03

The most recent spacecraft telemetry was acquired from the Canberra tracking station on Wednesday, April 30. 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.

April 26th marked the 5th anniversary of Cassini's first Venus flyby. Cassini is using a Venus-Venus-Earth- Jupiter trajectory. Each flyby provides a gravity assist that cumulatively will enable Cassini to reach Saturn in 2004.

The Command and Data Subsystem (CDS) Flight Software (FSW) checkout concluded this week with a successful optical navigation (OPNAV) test. Final activities for C36 included a reaction wheel assembly momentum unload, and uplink of the C37 background sequence.

The completion of the optical navigation test marks the conclusion of the engineering flight software checkout period. Both the Attitude Control and Command and Data subsystems have successfully demonstrated the full suite of capabilities afforded by the new software that will be used throughout orbital operations.

C37 began execution late Monday night. Initial activities included loading of Imaging Science Subsystem (ISS), Ultraviolet Imaging Spectrograph (UVIS), and Radio and Plasma Wave Science (RPWS) instrument expanded blocks from the background sequence, RPWS high-rate observations, an RPWS high frequency receiver calibration, and clearing of the attitude control high water marks. At the end of this week the spacecraft transitioned to reaction wheels in preparation for trajectory correction maneuver 19.

Optical navigation data from this weeks test have been processed by the Multimission Image Processing Laboratory (MIPL), including 18 Narrow Angle Camera (NAC) and nine Wide Angle Camera (WAC) images. The Navigation team has reviewed the data and reported that pointing was very good (within about five or six NAC pixels of the target) and that the exposures on 11th magnitude stars are good.

Mission Planning and Science Planning held a kick off meeting for the implementation of the science operations plan for tour sequences tour sequences S7/S8 this week, along with a project briefing for the cruise sequence C39.

An Archive Design Peer Review of the Cosmic Dust Analyzer (CDA), ISS, Radio Science Subsystem (RSS), and Visual and Infrared Mapping Spectrometer (VIMS) instrument team archive plans was held this week. Members of the Planetary Data System, instrument team representatives, and Instrument Operations personnel attended.

A Software Review Certification Requirement meeting was held for Composite Infrared Spectrometer FSW version 2.0.1. The software is due to be uplinked to the spacecraft in late May.

MIPL delivered an engineering version of the remote constraint checker tools to the ISS and VIMS science teams. The software will be used for validation of Instrument Operations Interface (IOI) files prior to delivery to IO. These tools allow a remote site to automatically deliver preliminary IOI files to MIPL, have them error/constraint checked there, and have the results returned to the remote site. During operations this will enable instrument teams to deliver error-free IOI files.

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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