Cassini Significant Event Report

For Week Ending 04/27/01

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Tuesday, April 24. The Cassini spacecraft is in an
excellent state of health and is operating normally. The speed of the
spacecraft can be viewed on the
"Present Position"
web page.

Recent spacecraft activities include automatic repair of the Solid State
Recorder (SSR) A, a Radio and Plasma Wave Science (RPWS) High Frequency
Receiver (HFR) calibration, a Reaction Wheel Assembly (RWA) momentum
unload, and uplink and successful checkout of a new 35.5kbps telemetry
mode. Previously, the highest useable telemetry rate was 22kbps. By
using the new 35.5kbps capability, Cassini can raise the downlink
telemetry rate by more than 50%.

Additional instrument activities include power-on of the Composite
Infrared Spectrometer (CIRS) followed by a boresight calibration, and
upload of a mini-sequence for the Cosmic Dust Analyzer (CDA). CDA powered
on, performed a checkout of its version 8.4 Flight Software, then switched
on the high voltages to reach a basic measurement mode. All activities
executed normally, and CDA is in a healthy and nominal state.

The Radio Science Subsystem (RSS) team obtained 4.25 hours of Ka-Band
Translator (KaT) 2-way data as part of continued testing of the KaT
module, one of four radios onboard the spacecraft. This is the longest
period of continuous KaT operation since early 1999, and is significant in
the on-going efforts to characterize the performance of the KaT in support
of the Gravitational Wave Experiment (GWE) system test, scheduled to begin
in early May.

The final Sequence Integration & Validation (SIV) approval meeting was
held for the Cruise 26 sequence. Uplink will occur later this week.

A week long Cross-Discipline Workshop sponsored by Cassini Science
Planning concluded this week. The goals of this workshop included the
identification of heavily conflicted periods, the division of the tour
into segments and the creation of Target Working Teams. Major progress
was made by all teams in all areas and the workshop was felt to be a great
success. Science Planning also hosted a Titan Orbiter Science Team (TOST)
meeting this week.

The Navigation Team has completed a study on the feasibility of raising
the minimum Titan flyby altitude to as high as 1050 km as a contingency in
case the actual Titan atmosphere precludes flying at the current minimum
of 950 km. The results of the study indicate that all Titan flybys and all
icy satellite flybys remain in the tour. The geometries of the Titan
flybys change only slightly. There is actually a small savings in
deterministic propellant cost.

Mission Support & Services Office (MSSO) personnel presented the Cassini
security and International Trade in Arms Regulation (ITAR) environment to
members of the JPL Executive Council. The Council was favorably impressed
and indicated that Cassini had taken a lead in handling NASA and
Government mandated security and ITAR issues in the JPL community. MSSO
also prepared flow diagrams outlining the process used to allow foreign
nationals access to JPL. These diagrams will be used to interface with
JPL International Affairs and other organizations associated with the
process, assist in developing and streamlining current MSSO procedures,
and may also help users in understanding the big picture of the ITAR

The Command and Data System (CDS) Flight Software team held a delivery
review for version RV70_11.3. This upgrade contains a patch to the fault
protection response for a tripped solid state power switch on the
magnetometer replacement heater. All requirements for functionality,
testing, and documentation were met and the patches were delivered to the
Project Software Library. Uplink of the new software will occur in May
during the C26 sequence.

A Delivery Coordination Meeting (DCM) was held for the Cassini
implementation of Multimission Spacecraft Analysis Software (CSAS) 6.3.
Although most of the subsystem remains unchanged, both the Inertial Vector
Propagator (IVP) and Predicts Generation Tool (PGT) had batch modes added,
while the Kinematic Prediction Tool (KPT) had batch mode added, constraint
monitor detect mode turned on and RWA output logic improved.

Mission Assurance released the draft Significant Risk List (SRL) for
flight team review. This list represents an initial cut at the high level
Program risks that will be managed using the Risk Management Process. Once
this list is reviewed and refined, it will be input into an electronic
Risk Management Tool.

Instrument Operations (IO) hosted a member of the CDA Team from the Max
Planck Institut fur Kernphysik, Heidelberg, Germany, for a week of
operations training sessions following last week's cross discipline
workshop. Representatives from Cassini's Uplink Office, IO, System
Engineering, and MSSO contributed with a variety of training. In an
effort to increase effectiveness, many of the sessions were made available
to program members who had previously expressed an interest in additional

In cooperation with the Cassini Program, and drawing from material
developed for the Cassini Web site, a planetarium program has been
developed for school children and debuted at the Howell Memorial
Planetarium in Greenville, South Carolina. Three different schools
attended the program with 125 students and 15 teachers in attendance.

On Friday, 4/20/2001, Cassini was featured on the "Astronomy Picture of
the Day" web site,

Two new Cassini 20-slide sets were submitted to Finley-Holiday Film
Corporation for production. Set #1, "A Trip to Saturn" highlights the
launch, trajectory, tour, and planetary flybys. Set #2, "Saturn System"
highlights the planet, satellites, rings, magnetosphere, and Titan. When
available, both sets may be obtained through Finley.

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