Cassini Weekly Significant Events for 01/17/02 – 01/23/02

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, January 23. The Cassini spacecraft is in
an excellent state of health and is operating normally. “Present
Position” web page, http://www.jpl.nasa.gov/cassini/english/where/ .

The C30 sequence continues to execute as planned. Science activities
this week include the completion of a Composite Infrared Spectrometer
(CIRS) functional test. This mini-sequence performed a functional
checkout as the instrument transitioned from science mode, to sleep
mode, and powered off. The Imaging Science Subsystem (ISS)
decontamination mini-sequence began execution, with the Visual and
Infrared Mapping Spectrometer riding along. The spacecraft was turned
to Spica with ISS taking a number of images using the Narrow Angle
Camera. The spacecraft then returned to Earth point with ISS
decontamination heater #1 and the ISS replacement heater left in the ON
state. Decontamination activities will continue through the end of the
month when a second set of images will be obtained.

Spacecraft activities included transition from Reaction Control
Subsystem to Reaction Wheel Assembly mode in support of the ISS
mini-sequence, a Command & Data Subsystem (CDS) Solid State Power Switch
trip counter reset, and an autonomous CDS Solid State Recorder memory
load partition repair.

In support of a Deep Space Network (DSN) request to test a new version
of their firmware, a DSN Block 5 Receiver firmware test
Immediate/Delayed Action Program (IDAP) was uplinked. The IDAP will
execute next week, putting Cassini into 82K downlink mode over DSS-15,
and returning to S&ER3 near the end of the pass.

The 27th Cassini Project Science Group (PSG) meeting concluded during
this reporting period. Titan Orbiter Science Team and Satellite Orbiter
Science Team meetings were held to continue working integration issues
for the Titan and icy satellite flybys. Also during PSG week the
Cross-Discipline Workshop’s Equatorial Splinter Group was reactivated
to re-segment the tour prior to the Titan 3 (T3) flyby. The
re-segmentation was required due to the new probe mission design. The
group successfully segmented the tour for this time
frame and allocated the segments to the appropriate Target Working
Teams.

Mission Planning gathered science response and impacts to proposed
trajectory tweaks for tour. The tweaks included moving ring plane
crossings to reduce the probability of dust impacts to the spacecraft
and instruments. A presentation on the findings will be made next week.
Archiving status reported by Instrument Operations indicated that many
of the instrument teams have made progress identifying their data sets
and working with the Planetary Data System (PDS) to design archive
volumes and data processing systems. The Huygens Probe PDS
representatives have been identified, and work to develop the Huygens
PDS archive has begun. Radio Science plans to archive reduced products
including atmospheric T-p profiles, ionospheric electron density
profiles, ring opacity profiles, GM and higher order results from
various gravity fields.

Uplink Operations – Mission Sequence Subsystem (ULO-MSS) internal status
meetings have assessed progress towards the MSS D8 software delivery
date in May of this year. While some threats were identified, there was
only one task that could not be handled within the current ULO-MSS
margin policy. Additional analysis incorporating new information
indicates that the work can probably be done within the policy if some
tasks are reallocated.

After review at a previous Cassini Design Team meeting (CDT), comments
have been incorporated and a new plan designed to deal with system-level
vs. instrument internal commands. The revised plan was presented at
this week’s CDT.

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.