Cassini Significant Event Report

For Week Ending 05/28/04

The most recent spacecraft telemetry was acquired from the Madrid tracking station on Wednesday, May 26. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" web page located at .

On-board activities this week included the Imaging Science Subsystem (ISS) Titan movie which searches for evidence of cloud motion to measure winds. ISS also continued to study the orbits of the ring-region satellites to improve our understanding of short- and long-term dynamical evolution. The Ultraviolet Imaging Spectrograph (UVIS) continues to map the Saturn magnetosphere in neutral and ion photon emissions to derive the distribution and density of atomic and molecular species. Deep space calibrations were performed for the Composite Infrared Spectrometer (CIRS), and a high frequency calibration for the Radio and Plasma Wave Science (RPWS) instrument. The ISS NAC was commanded to perform a power-on reset to clear any possible residual problems prior to some critical Optical Navigation activities. These activities then occurred without incident.

Remaining on-board activities centered on preparations for Trajectory Correction Maneuver 20. This maneuver is significant in that it adjusts the spacecraft's orbit for its approach to Saturn, and is the same type of maneuver that will be used for Saturn Orbit Insertion (SOI). This week a checkout was performed for Rocket Engine Assembly-B, the main engine cover was opened, and the oxidizer side of the propulsion system un-isolated. The spacecraft is now ready to support TCM-20 on May 27, 2004.

Starting on Monday, May 24, the Cassini Imaging Team increased the frequency of its postings of images to one per day (five days per week) for the enjoyment of scientists and members of the public alike.

The Multi Mission Image Processing Laboratory (MIPL) supported the generation and delivery of three sets of 'critical' Optical Navigation images in the last week. Two of the events occurred on non-prime-shift and were staffed for potential manual intervention. All these deliveries were made successfully and on-time by the automated processes - no intervention required.

In the last week, 625 ISS images arrived and were distributed along with 369 Visual and Infrared Mapping Spectrometer (VIMS) cubes. The total number of ISS images acquired since the start of Approach Science is now 7413, and the number of VIMS cubes is 1311.

In support of the Phoebe encounter, the flight team is holding an Operations Readiness Test (ORT) for the Phoebe Live Update Process. This week the files generated during last week's live update process were run through the Integrated Test Laboratory for validation. In addition, it was decided to forgo the remaining portions of the ORT to allow for an earlier Navigation convergence and a more relaxed schedule for actual Phoebe operations.

The port #1 end-to-end pointing analysis for tour sequences S29 and S30 has been completed. The Teams will now review the analysis reports and correct any problems in time for preliminary port #2 on June 7.

The science operations plan implementation process for tour sequences S31 and S32 began this week. A Tour Process meeting was held Wednesday, May 26, to discuss the impacts the new reference trajectory has on the integrated science plan and the possible options available to deal with those changes.

A sequence change request approval meeting was held as part of the process to develop tour sequence S03. Four requests were approved.

A delivery coordination meeting was held for Navigation software version T1.4. During last week's internal SOI review, Navigation identified two "must-do" fixes for this software. One was for ARDVARC, the automated radiometric data visualization and real-time correction software, and the other for PVTOEXP which converts spacecraft trajectory "P" files from NAV-IO format to "Export" DSN format. The 4.1 version was approved and has been installed for operations use.

The Saturn Observation Campaign (SOC) is a Cassini informal education program, comprised of about 300 mostly amateur astronomers in 43 states around the US and in 42 countries around the world. A Saturn Observation Campaign observing event will be held at Monrovia's Library Park at the corners of Myrtle and Lime Streets, in Monrovia, California from 7:30 p.m. to 10:00 p.m. Saturday May 29. There will be at least two and maybe more telescopes aimed at Saturn and Jupiter or the moon. A local middle school science class has been invited and a nice crowd is expected. Saturn will look best earlier rather than later in the evening.

Saturday night, May 22nd, was also the date of the Griffith Observatory Star Party, hosted by the Los Angeles Amateur Astronomers and the LA Sidewalk Astronomers. The Griffith Observatory event runs from 2:00 p.m. for solar to 10:00 p.m. once a month. The Griffith Observatory satellite is located immediately south of the LA Zoo and the Autry Museum in the northeast corner of Griffith Park, Glendale, California.

Saturn is getting low in the western sky, and by next month, it won't be visible again - at least at a decent hour for viewing - until late 2004. This weekend will be a great time to see Saturn, with Mars nearby, Venus and Jupiter and even the 3-day waxing moon.

As Saturn grows closer through the eyes of the Cassini spacecraft, both Cassini and the Earth-orbiting Hubble Space Telescope snapped spectacular pictures of the planet and its magnificent rings.

Cassini is approaching Saturn at an oblique angle to the Sun and from below the ecliptic plane. Cassini has a very different view of Saturn than Hubble's Earth-centered view. For the first time, astronomers can compare views of equal sharpness of Saturn from two very different perspectives. For more information go to: and

Five Cassini images were released in the past week. These images are available on the gallery section of the Cassini website

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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