Cassini Significant Event Report

For Week Ending 04/13/01

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, April 11. 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 included a Reaction Wheel Assembly (RWA)
unload and a High Water Mark clear. The Imaging Science Subsystem (ISS)
observations continued this week. Additional Instrument activities included
a Magnetospheric Imaging Instrument (MIMI) Ion and Neutral Camera (INCA)
Positive Collimator high voltage test, Flight Software (FSW) checkout for
the Composite Infrared Spectrometer (CIRS), conclusion of the Radio and
Plasma Wave Science (RPWS) Periodic Instrument Maintenance, and an RPWS HFR
calibration. The Cosmic Dust Analyzer (CDA) performed a checkout of their
existing Version 7.2 FSW then powered off. Later in the week Version 8 FSW
was uplinked with checkout to be scheduled for a later date.

The Radio Science Subsystem (RSS) Operations Interface Test/Mission
Verification Test (OIT/MVT) was performed this week in preparation for the
Gravitational Wave Experiment (GWE). A comprehensive series of tests
spanning three days was executed. The main objectives were three-fold:

  1. Consistently lock the KaT to the Ka-band uplink.
  2. Stay locked to the Ka-band uplink.
  3. Characterize the phase stability of the locked KaT.

The first day of testing saw the KaT locking on several occasions. In a
unique event, with the regular X-band uplink also operating, Cassini
became the first spacecraft ever to handle dual uplinks from a single DSN
station. RSS personnel also observed the longest stable uplink to the KaT
since the original checkout over a year ago. The nominal plan for day two
of the test included sending real-time commands to cycle the power to the
KaT for each uplink attempt. The "normal" wait time between power
OFF/power ON cycles has been 30 minutes. One opportunity was used to cut
that time to 5 minutes. The result was that the KaT reset itself and came
up in the expected frequency region. On the final day of testing, eleven
different Ka-band uplinks were transmitted, with the KaT power cycled
between each uplink. The KaT was seen to lock ten out of eleven times.
With the test now concluded, the compiled data will be analyzed by the RSS
team and the Italian Space Agency (ASI). Further testing is scheduled for
next week.

RADAR's results from the January measurements of Jupiter's synchrotron
radiation were recently presented at two conferences in Europe, the
European Geophysical Society meeting and the International Workshop on
Planetary Radio Emissions V. These data were the first ever obtained of
the Jupiter synchrotron emission in the 2 cm wavelength range. This
wavelength is unattainable from Earth-based telescopes. Cassini's
radiometer data, which were able to tie down the previously unexplored
upper limit, are being combined with new data acquired simultaneously in
the 20 cm and 90-cm wavelength ranges by ground-based partners in this
experiment (the DSN, the Very Large Array, and the Goldstone-Apple Valley
Radio Telescopes). These combined data sets are being used to create new
maps of the Jovian energetic particle distribution within Jupiter's
radiation belts.

Instrument Operations and the Multi Mission Image Processing Laboratory
processed and delivered 702 Imaging Science Subsystem (ISS) Wide-Angle
Camera (WAC) asteroid dustband images this week.

The Spacecraft Operations Office (SCO), Cassini Program Manager and
Project Scientist supported the fourth Huygens Recovery Task Force (HRTF)
meeting held at the Alcatel facility in Cannes, France. This was the first
joint meeting with the Huygens Science Working Team participating. The
purpose of the meeting was to review the HRTF work done so far and to
select the recovery scenarios that will be subjected to a detailed study
in the next months. The HRTF has established a very good understanding of
the receiver performance as a function of the three main parameters:
Signal-to-noise ratio, received frequency, and data bit transition
probability. Additional technical work that must be done has been
identified to allow a complete evaluation of the respective values of the
recovery scenarios.

A team of FSW and spacecraft experts from SCO reviewed the Saturn Orbit
Insertion (SOI) system mode test plan. This is a series of Integrated Test
Lab (ITL) system mode tests that will examine the interaction of flight
software fault protection with the critical SOI sequence. The plan calls
for weekly tests through next fall. The team suggested a re-ordering of
the test cases and made a few refinements to the tests.

A peer review of the Solid State Recorder (SSR) Management Tool
requirements was held, which looked into possible scenarios for data

Science instrument teams submitted their files for the first input port
for the development of the C27 sequence.

The URL for the Navigation Ancillary Information Facility (NAIF) article
to the Science Information Systems Newsletter (SISN) given last week might
have been incorrect. The correct URL is: .

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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