Cassini Significant Events for 04/10/03 - 04/16/03

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Cassini Significant Events
for 04/10/03 - 04/16/03

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, April 16. 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/operations/present-position.cfm .

Command and Data Subsystem (CDS) Flight Software (FSW) checkout
activities continued this week with playback of data from last week's
Probe Solid State Recorder Dual Record Demo, enabling of the CDS Solid
State Recorder (SSR) Auto-Repair function, a RADAR Instrument Expanded
Block (IEB) Exercise with Telemetry Mode Checkout, power on and IEB
checkouts for Radio and Plasma Wave Science (RPWS) and Magnetospheric
Imaging Instrument (MIMI), clearing of the Attitude Control System (ACS)
high water marks, and powering on of the Magnetometer Subsystem (MAG)
and Composite Infrared Spectrometer (CIRS).  The IEB checkouts for
RADAR, RPWS, MAG, and CIRS activities were nominal. Due to a timing
error, MIMI rejected the commands comprising the IEB load test.  The
cause is understood and the test will be repeated in a later sequence.
No recovery commanding is necessary.

On DOY 098, an absolute timed mini-sequence and an Immediate/Delayed
Action Program (IDAP) were executed on the spacecraft to perform a test
of the Probe Relay telemetry mode with SSR Dual Record. The execution of
the mini-sequence was very similar to the Probe Relay critical sequence,
with fault protection and other critical commands removed. The purpose
of the playback was to demonstrate the priority playback capability of
Probe data over two separate passes.  The play back and downlink were
completely nominal. However, the Real-Time broadcast of Probe data to
the Huygens Probe Operations Center (HPOC) failed.  The problem was
identified as a telemetry broadcast buffer overflow, caused by a
mismatch in data rates between the spacecraft data rate and the data
lines to HPOC.  Post pass querying of the playback data by HPOC was
successful. Spacecraft Office, Mission Support and Services Office,
Instrument Operations, System Engineering, and Huygens personnel at JPL
are working the issue. Plans are already in place to test a higher
capacity data line to HPOC which will be installed later this year.

The Huygens Team has begun to review the data from the dual record
demonstration, and perform gap analysis at their facility in Europe.
Analysis is expected to be complete next week.

Testing of the first five days of the C37 background sequence, and
Trajectory Correction Maneuver (TCM)-19 in system mode have completed
successfully in the Integrated Test Laboratory.  The preliminary
Sequence Integration & Validation package for C37 was also released for
review, and a waiver approved for the CIRS FSW checkout activity.

Contingency planning for the TCM-20 timeframe has been completed. The
plan deals with potential issues in the operation of the Main Engine
Assembly cover and with pyro sequence for bringing the oxidizer side of
the bi-propellant system online.

Science Planning Virtual Team development for the C39 sequence kicked
off this week.  C39 will use the 2-port, 8-work-weeks cruise development
process. The process will conclude in mid June.  A project briefing for
this sequence will be held in two weeks.

Multimission Image Processing Laboratory (MIPL) personnel performed a
short performance test of downlink and reconciliation processing. The
test was monitored and analyzed by system analysis software.  The
results showed that the machine loading expected during the tour will be
adequately accommodated by planned hardware procurements. Acceptance
testing has begun for MIPL D30 software. D30 is scheduled for delivery
in July of this year.

System engineering held a meeting for team, office, and project
management to present options and recommendations for ground data system
workstation operating system migration.  The decision was reached to
proceed with Mission Sequence Subsystem (MSS) and Kinematic Prediction
Tool-Inertial Vector Propagator (KPT-IVP) development on the Solaris 7
environment for delivery in mid-July. The developers will then port
these tools to either Solaris 8 or Solaris 9, depending upon the results
of concurrent Solaris 9 testing.

A delivery coordination meeting was held for the Navigation Ancillary
Information Facility toolkit version N0055.

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.

Cassini Outreach
Cassini Mission to Saturn and Titan
Jet Propulsion Laboratory
California Institute of Technology
National Aeronautics and Space Administration



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