Cassini Significant Event Report

For Week Ending 11/02/01

The most recent spacecraft telemetry was acquired from the Canberra
tracking station on Wednesday, October 31. The Cassini spacecraft is in an
excellent state of health and is operating normally. Information on the
spacecraft's position and speed can be viewed on the
"Present Position"
web page.

Recent instrument activities include a Radio and Plasma Wave Science
(RPWS) High Frequency Receiver calibration, a Composite Infrared
Spectrometer boresight calibration, and an Ultraviolet Imaging
Spectrograph (UVIS) Interplanetary Hydrogen Survey and Spica observation.
Engineering activities taking place onboard the spacecraft this week
include a static phase error test to characterize the spacecraft Deep
Space Transponder uplink receiver tracking, and the final S-band pattern
calibration for the Huygens Probe radio system. A minisequence uplinked
last week executed and overlaid the Attitude Control Subsystem (ACS)
momentum bias commands from the background sequence with new updated
values produced by the ACS team.

In preparation for the upcoming 40-day Gravitational Wave Experiment, the
Radio Science Subsystem (RSS) team conducted a dataflow test in order to
verify data paths in the RSS Ground Data System. DSN station personnel
were familiarized with the monopulse system configuration, calibration,
and operation, and flowed the monopulse monitor data back to JPL. RSS also
conducted a long Ka-2-band track, with the various subsystems performing
extremely well. Other activities performed in preparation for the GWE
include an Ultra-Stable Oscillator characterization, a boresight
calibration, and an RSS quiet test with the Fields, Particles, and Waves
(FPW) instruments to determine if the RSS can detect the FPW instruments
in their "noisy" states.

The Imaging Science Subsystem (ISS) post-warm-up images were downlinked
for analysis. The 15 images were planned in support of the UVIS Spica
observation, and were examined for potential changes relative to the
pre-warm-up images. Preliminary results show a change in the character of
the anomaly with the halo gone but more spreading of the star image than
before. ISS also performed a scattered light observation, in an effort to
resolve an anomaly observed in C25 when an ISS observation received far
more light than expected. This current observation included a series of
scans across the sky to see how much scattered light ISS gets at different
distances from the sun for a selection of different orientations, to see
if reflection off another part of the spacecraft is causing the extra
light seen by ISS.

The RADAR team performed an instrument calibration, which involved
collecting radiometry data of two microwave sources while executing
repeated box scans. These scans were performed as close as possible to
the power-on of the instrument so the RADAR team can better characterize
their warm-up calibration requirements. Currently, RADAR is requiring 3
hours of warm-up for radiometry in science planning, which causes them to
frequently conflict with other instrument teams. They are hoping to be
able to reduce their warm-up time based upon the understanding they
receive from analyzing this data.

In conjunction with the ISS scattered light observation, the
Magnetospheric Imaging Instrument (MIMI) performed a test of the Ion and
Neutral Camera (INCA) collimator. The test ramps the INCA high voltage
collimator plates up to operational voltage on the positive plate, leaving
the negative turned off. This is done in coordination with the scattered
light test to provide a condition of sunlight on the collimator plates,
but no thruster activity. It tests the theory that this configuration
will prove to be noise-free for RPWS and Cassini Plasma Spectrometer
(CAPS). RPWS supported this test by monitoring its data for interference.

The C29 Sequence Team development phase has been completed. The Final
Sequence Integration & Validation Approval meeting was held, and all
Cassini teams approved the sequence for uplink. The C29 sequence will be
uplinked on Nov. 1 and will begin execution on Nov. 4. This sequence
includes a Visual and Infrared Mapping Spectrometer radiator test, a
5-pass Probe Relay Test, the first of three GWEs, an Attitude Control
Subsystem (ACS) Periodic Instrument Maintenance, and a Cosmic Dust
Analyzer flight software upload and checkout.

The Science Uplink Verification (SUPV) activity for three Titan flybys has
been completed, and the SUPV for three Icy Satellite flybys begun. The
Science Planning Team is in the process of generating a final report on
the Titan SUPV, which will include lessons learned from this exercise. A
full suite of Target Working Team (TWT) integration team meetings was held
last week to continue with the integration of the tour. Semi-monthly
Satellite and Titan Orbiter Science Team meetings are now being held on

The Attitude Control Team has released its the third quarter report. In
summary, the attitude control system is operating properly. There were no
fault protection entries, all trends are as expected, and all scheduled
activities were executed normally.

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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