Status Report

Cassini Significant Events for 09/16/04 – 09/22/04

By SpaceRef Editor
September 24, 2004
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The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, September 22. 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

Activities for the currently executing sequence S04 included approving and
uplinking numerous files, including files for probe battery depassivation,
resetting of probe relays, an Instrument Expanded Block for the Ion and
Neutral Mass Spectrometer (INMS), and real-time commands for the
Magnetospheric Imaging Instrument (MIMI) and the Cassini Plasma Spectrometer

On Sunday, the first battery depassivation sequence was executed on the
Huygens probe. The purpose of the depassivation activity is to remove the
thin layer that forms within the lithium-sulphur-dioxide battery cells on
the surface of their electrodes. This layer, which builds up naturally over
time, helps the cells to retain their charge during the long Cassini cruise
phase but is undesirable for operations during the Probe mission

The sequence powered on the probe using orbiter power as usual but then
sequentially brought each of the five probe batteries on line for five
minutes. This was the first time the batteries’ performance has been
monitored since before launch. The activity was completely nominal and
indicates that all five probe batteries are healthy and ready to support the
complete Huygens mission including the pre-heating option. The second
depassivation activity is scheduled for December 5.

Other on-board activities this week included a Radio Science Subsystem (RSS)
Periodic Instrument Maintenance activity, a characterization of the
Ultra-Stable Oscillator, and a calibration of the High-Gain Antenna
boresight. This is the first time RSS has used an Inertial Vector
Definition file to produce and implement an actual spacecraft activity. The
activity was performed successfully.

The Imaging Science Subsystem (ISS) focused on long duration movies looking
for ring ‘spokes.’ Magnetospheric and Plasma Science (MAPS) instruments
continued to search for upstream plasma activity and monitored the solar
wind. Optical Navigation took images twice a day to refine Cassini’s
trajectory and improve knowledge of the satellites’ orbits.

In the last week, 1064 Imaging Subsystem (ISS) images were received along
with 70 Visual and Infrared Mapping Spectrometer (VIMS) cubes. Since
Approach Science began in January of this year, 22291 ISS images and 5309
VIMS cubes have been returned.

An official port 1 delivery was made this week for the Science Operations
Plan (SOP) Implementation process for tour sequences S37/S38, and the
official port delivery was made as part of the S07 SOP Update process. The
team files have been merged for both deliveries and a report published
identifying any issues. The wrap-up meeting for the SOP Implementation
process for tour sequences S37/S38 was held on 9/22/04 and these products
will be archived for later use. The SOP Implementation process for tour
sequences S39/S40, as well as the SOP update process for tour sequence S08,
began on the same day.

Sequence development continued for S05 this week with a Sequence Change
Request (SCR) and Waiver Approval meeting where five SCRs were approved.
Preliminary inputs from all teams were also due this past week. Results
from the RADAR Team’s analysis of the Integrated Test Laboratory (ITL) tests
for the Ta flyby show that the actual pointing profile generated in the test
matches very well with the intended design.

The Spacecraft Operations Office (SCO) held the Attitude Control Flight
Software A8.7.1 Uplink Readiness Review on September 20, 2004. This flight
software load contains updated parameters necessary for the Probe Mission
and beyond. The A8.7.1 flight software is due to be uplinked to the
spacecraft Solid State Recorders starting September 28, with the checkout
starting October 2, 2004.

An operational delivery of Navigation software version T1.5 was made to the
project on 9/22/04.

A Sequence/Software Monthly Management Review was held on 9/16/04. Status
was provided on probe sequence development as well as software status from
Attitude Control Subsystem, Navigation, Mission Sequence Subsystem, and
Mission Support & Services Office.

For the most recent Cassini information, press releases, and images, go to

The Cassini-Huygens mission 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, manages the
Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington,
D.C. JPL designed, developed and assembled the Cassini orbiter.

SpaceRef staff editor.