Cassini Significant Events for 04/11/02 – 04/17/02
The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, April 17. 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/cassini/english/where/ .
The primary activity on board the spacecraft this week was Probe
Checkout (PCO) #9. The checkout was completed successfully. However,
during the checkout, Goldstone Deep Space Station (DSS) 25 was required
to end track and stow its antenna early due to high winds. The resulting
telemetry outage caused the loss of PCO #9 real-time data and was
expected to continue though the time allotted for PCO recorded data
playback. At the request of Huygens Probe Operations Center personnel,
with Cassini Program Manager concurrence, and with prior notification
given to affected instruments, the Spacecraft Office built a real-time
command to inhibit writing of Magnetospheric and Plasma Science (MAPS)
data on the Solid State Recorder. This preserved the PCO data for
playback at the next scheduled track. About 20 hours of MAPS data was
lost. The pass over DSS 45 was then used to playback the PCO data and
resume normal C31 activities.
Additional instrument and spacecraft activities included the uplink of
real-time commands to modify the Radio and Plasma Wave Science
Instrument Expanded Block to fine tune resolution of data collected,
clearing of the ACS high water marks, an autonomous CDS Solid State
Recorder memory load partition repair, a demonstration over DSS 45 of
the new Version 26.4 Command System, and uplink of a Privileged Action
Program to disable/enable the Solid State Power Switch trip Fault
Protection in support of the Probe checkout.
Science Planning reported that all Target Working Teams made the
delivery for the Science Operations Plan integration activity for orbits
15 through 20. The Instrument Operations Science Data Archive Engineer
is conducting a Planetary Data Archive Workshop in conjunction with the
Huygens Science Working Team meeting being held this week in Paris,
France.
After last week’s delivery coordination meeting for Cosmic Dust Analyzer
flight software, it was identified that V9 may generate invalid packet
IDs. Workarounds were discussed and a final decision regarding uplink
will be determined by next week.
Mission Support and Services Office (MSSO) personnel met with Radio
Science and the DSN Network Operations Project Engineer to discuss
uplink transfers for the next Superior Conjunction Experiment. During
the Gravitational Wave Experiment last December, about a dozen uplink
transfers failed, each causing more than 2 hours outage in prime mission
science data. The most likely cause identified was the setting DSS
waiting too long to initiate tune-out. It was resolved that a briefing
message will be sent to the DSN specifying begin tune-out time based on
Spacecraft Office telecom analysis.
All teams and offices supported the Cassini Monthly Management Review.
The Program Manager gave a presentation to the JPL Executive Council on
the issue of providing real-time communications during the SOI burn by
doing the burn at Earth-line attitude. It is feasible to provide
telemetry during all of the burn except for a period where the
spacecraft is occulted by the rings, but at a cost in science return and
propellant usage. Further studies were requested.
MSSO personnel gave a talk and museum tour to attendees of a NASA
Administrative Issues Conference held at the Jet Propulsion Laboratory.
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.
