Cassini Significant Event Report

For Week Ending 02/06/98

MSO Significant Events input for week of Friday 01/30 through Thursday 02/05:


Spacecraft Status:


The Cassini spacecraft is presently traveling at a speed of approximately 124,000 kilometers/hour (~77,000
mph) with respect to the Sun and has traveled approximately 281 million kilometers (~176 million miles) since
launch last October 15.


The most recent Spacecraft status is from the DSN tracking pass on Thursday, 02/05, over Madrid. The
Cassini spacecraft is in an excellent state of health and is operating nominally, with the C6 sequence executing
onboard. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page (http://saturn.jpl.nasa.gov/operations/present-position.cfm)


Inertial attitude control is being maintained using the spacecraft's hydrazine thrusters (RCS system). The
spacecraft continues flying in a High Gain Antenna-to-Sun attitude. It will maintain the HGA-to-Sun attitude,
except for planned trajectory correction maneuvers, for the first 14 months of flight.


Communication with Earth during early cruise is via one of the spacecraft's two low-gain antennas; the antenna
selected depends on the relative geometry of the Sun, Earth and the spacecraft. The downlink telemetry rate is
presently 40 bps.


Spacecraft Activity Summary:


From Friday, 01/30, through Sunday, 02/01, there were no changes in spacecraft configuration.


On Monday, 02/02, and Tuesday, 02/03, a maintenance activity was performed on the SSR Flight Software
Partitions. This activity, scheduled approximately every two weeks, repairs any SSR DBEs which have
occurred in the code-containing portions of the Flight Software partitions during the preceding period.
Monday's activity performed the repair; Tuesday's activity read out the results of the repair and reset DBE
counters in the repaired partitions. Tuesday's telemetry indicated that two DBEs were successfully repaired
and one DBE was located in an unused portion of a partition (such DBEs are identified by this procedure and
repaired by a different procedure).


Also on Tuesday, 02/03, the Solid State Recorder (SSR) record and playback pointers were reset, according
to plan. This housekeeping activity, done approximately weekly, maximizes the amount of time that recorded
engineering data is available for playback to the ground should an anomaly occur on the spacecraft.


On Wednesday, 02/04, and Thursday, 02/05, there were no changes in spacecraft configuration.


Upcoming spacecraft events:


Events for the week of 02/06 through 02/12 include: a reset of the SSR pointers (02/09), a Read-out of the
Propulsion Module Subsystem (PMS) Mass Properties (02/12), in preparation for TCM-2 which is
scheduled for February 25.


Two science activities are being considered for the Venus 1 flyby in April. The first is a search for Venus
lightning by the Radio and Plasma Wave Science instrument; the second is a check of the RADAR bounce
capability. If these activities are approved, they will be added to the sequence. No off-sun-line maneuver is
required.


DSN Coverage:


For the next month or so, there will be an increase in DSN coverage for Navigation purposes, as the second
and third Trajectory Correction Maneuvers (TCMs) approach. Over the past week Cassini had 8 track
periods (01/30, 01/31- 3 passes, 02/02, 02/03, 02/04, 02/05). In the coming week there will be 7 DSN
passes, Friday (02/06), Sunday and Monday (02/08, 02/09), and 4 passes occurring from Tuesday through
Thursday (02/10 - 01/12).



Additional information about Cassini-Huygens is online at http://saturn.jpl.nasa.gov.


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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