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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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