Cassini Significant Event Report

For Week Ending 05/21/04

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, May 19. 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 .

After activating, loading instrument expanded blocks, and initializing various instruments, S01, the first tour sequence, began data collection activities. Unique activities in S01 include trajectory correction maneuvers 20 and 21, the first Inertial Vector Propagator (IVP) live update, and the only Phoebe encounter in the tour.

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 known satellites to improve 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. The Composite and Infrared Spectrometer (CIRS) collected the first in a series of long integrations of Saturn for temperature data. The ISS continued with some standard searches for satellites embedded in the outer part of the rings and outside the main rings.

On Saturday, May 15th, the first Radio Science Subsystem (RSS) activity during tour took place. This consisted of a 4-hour long Ultra Stable Oscillator (USO) characterization, and was also an opportunity to continue with the Ka-band Translator recovery attempts.

In the last week, 684 ISS images arrived and were distributed along with 77 Visual and Infrared Mapping Spectrometer (VIMS) cubes. The total number of ISS images acquired since the start of Approach Science is now 6655, and the number of VIMS cubes is 843.

In support of the Phoebe encounter, the flight team is holding an Operations Readiness Test (ORT) for the Phoebe Live Update Process. This week an ORT walk-through was held along with a Live Update ORT Go/No-Go meeting, and a Phoebe ORT Command approval meeting. Once complete, the files generated during this test will be run through the Integrated Test Laboratory for validation.

Sequence development of S02 continued this week with release for review of the S02 Preliminary Sequence Integration and Validation 2 (PSIV) stripped subsequence products. Ten sequence change requests (SCR) were dispositioned at the S02 PSIV SCR approval meeting. A kick-off meeting was held for the S03 Science and Sequence Update Process.

The Science Operations Plan (SOP) Implementation process for tour sequences S31 and S32 began this week. Sequences S27 and S28 wrapped up, and S29 and S30 were merged for official port #1 and are currently being reviewed.

An updated Cassini reference trajectory was released on 13 May 2004. The new trajectory results from improvements in satellite ephemeris knowledge, and enables the navigation team to maintain key science objectives while controlling propellant expenditure within acceptable limits.

SOI readiness reviews this week included a presentation to the Tom Young committee and an internal Project review. Both reviews resulted in some actions being accepted, but the consensus of both was that the Project is well postured for the upcoming SOI.

Members of the flight team traveled to the DSN complex at Goldstone, California, to perform an Emergency Control Center (ECC) demonstration. These demos occur periodically to confirm that emergency command capability is still active and available should the need arise. Unfortunately, a reoccurrence of a 2-way acquisition failure at DSS-25 invalidated the demo. The team is currently looking at options for rescheduling the test.

A new version of the Multi-Mission Image Processing Laboratory software set was accepted for operations at a Delivery Review. Four approved additions were made to enhance robustness and eliminate some uplink workarounds. Additional reviews were held for Spacecraft Operations Office tools Telemetry Input Gap Analyzer and Reporter V1.0, Kinematic Prediction Tool 10.3.5, and IVP 10.3.3.

Approximately 40,000 guests visited JPL and the Cassini display last weekend for the laboratory's annual open house. The Cassini display included a half-scale model of the spacecraft, and screened the planetarium show "Ring World." Members from the flight team volunteered time at the different Cassini exhibits throughout the weekend.

This week's image is a single filter narrow angle camera view of Titan. This and previous images can be accessed 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.

Media Relations Office

Jet Propulsion Laboratory

California Institute of

National Aeronautics and Space

Pasadena, Calif. 91109.
Telephone (818) 354-5011