Cassini Significant Events for 04/25/02 – 05/01/02

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, May 1. 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
http://saturn.jpl.nasa.gov/cassini/english/where/ .

This week marks the four year anniversary of the Cassini Venus 1 flyby.
Onboard activities this week included Periodic Instrument Maintenance
for the Ultraviolet Imaging Spectrograph, Imaging Science Subsystem
decontamination activity #1, clearing of the ACS high water marks, and
an autonomous CDS Solid State Recorder memory load partition repair.

The C32 sequence was approved at the Preliminary Sequence Integration
and Validation meeting. The sequence will be uplinked and begin
execution next week. As part of validation for the new command system,
C32 will be radiated using the new Spacecraft Message File format rather
than the old Command Packet File. C32 will be the largest file sent so
far using the new command system.

Cassini participated in a DSN array test at the DSS complex in
Goldstone, California. Cassini results indicated the test was a success
with a 1 dB gain in signal level and 3 dB gain in telemetry signal to
noise ratio. DSN personnel are still analyzing test data.

Science Planning is preparingAdmi the kickoff of the first tour Science
Operations Plan (SOP) implementation activity. This process will
implement sequences 9 and 10 of the tour. An SOP implementation
schedule has been developed using two concurrent processes and two
sequences per process approach, and a kickoff package is being
generated.

The Huygens Implementation team held its second quarterly progress
meeting at Alcatel in Cannes. The team has agreed upon a set of flyby
conditions that are independent of the decision to pre-heat the probe
prior to entry into Titan’s atmosphere. The decision on whether to
pre-heat the probe will be made later after a complete assessment of the
impact can be made by the probe instruments. Other topics discussed were
link budget updates, mission analysis and robustness studies, and entry
sensitivity studies.

The Navigation team has released a new reference trajectory for the
orbital tour and the remainder of interplanetary cruise. This new
trajectory includes the latest flyby geometry for the revised Huygens
mission and the final icy satellite adjustments and changes made for
G-ring crossings. This trajectory will serve as the reference for the
Science Operations Plan that will begin development in May.

An updated strawman presentation of DSN coverage to be requested for
revs 20 through end of tour was presented at this week’s Mission
Planning Forum. Discussion included the plan’s consistency with overall
data volume requirements, navigation tracking requirements, orbital trim
maneuver placement, sequence boundaries, Target Working Team boundaries,
and engineering events.

A meeting was held to finalize Uplink Operations development of the
Automated Sequence Processor. A preliminary version will be available
in the fall of 2002, with a final version being delivered in fall of
2003. This software subsystem will be a Cassini adaptation of what is
already in use within the Mars Program. It will allow for a more
automated way to process real-time command requests from remote users.

Mission Assurance coordinated the first Quarterly Risk Team Meeting, to
assess and re-assess risks in the Cassini Significant Risk List. This
meeting produced some valuable discussion on risk issues and focused on
addressing Cruise Risks. Four new consumables risks were identified,
for addition to the Significant Risk List (SRL). Future Risk Team
Meetings will be scheduled to address SOI, tour, and Probe mission
risks.

Mission Assurance completed a trend analysis of sequence and command
errors experienced since launch. Error rates were trended with the rate
of uplink activity to the spacecraft. Trend analysis indicates that the
error rate has decreased since launch, and despite periodic
fluctuations, has remained relatively stable.

An RFP was released this week for a Saturn/Cassini-Huygens updateable
planetarium show. Total show length will be approximately 20-30
minutes. The Cassini/Huygens mission seeks proposals for shows serving
both the small and rural planetaria community through the mid and upper
range community. The initial version of the show is to be ready for
release in 2003 and will highlight the launch, cruise flight, flyby of
Jupiter, approach to Saturn, and the events that will occur upon arrival
at Saturn. A second version is planned to be released in mid-2005.

Outreach staff traveled to Berkeley, California to meet with individuals
from the Bay Area Writing Program (BAWP) and project FIRST. This meeting
was the first organizational step toward implementation of Cassini’s K-4
language and reading program.

Cassini is a cooperative project of NASA, the European Space Agency and
the Italian Space Agency. The Jet Propulsion Laboratory, a division of
the California Institute of Technology in Pasadena, Calif., manages the
Cassini mission for NASA’s Office of Space Science, Washington, D.C.