Cassini Significant Event Report

For Week Ending 06/12/98

Spacecraft Status:


The Cassini spacecraft is presently traveling at a speed of approximately 124,000 kilometers/hour (~77,000
mph) relative to the sun and has traveled approximately 699 million kilometers (~435 million miles) since
launch on October 15, 1997.


The most recent Spacecraft status is from the DSN tracking pass on Friday, 06/05, over Goldstone. The
Cassini spacecraft is in an excellent state of health and is executing the C8 sequence nominally. 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 to fly 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.


For the next several months, due to increasing range from Earth and relatively high angles with respect to the
Low Gain Antenna boresight, the DSN tracking passes for Cassini will be dedicated either to command and
telemetry (for spacecraft activities and health monitoring) or to Navigation ranging data (for orbit
determination). This approach manages the available telecommunications signal strength, directing it to either
command/telemetry or Navigation, according to plan. Telecommunications link performance will improve
again this Fall.


Spacecraft Activity Summary:


On Friday, 6/05, an MRO was performed to collect additional data stored in memory when the backup CDS
computer (CDS-A) underwent a reset at the end of April. See the significant events report for 05/22-05/29
for background information. If additional readouts are needed to pursue the matter, they will be performed
over presently scheduled DSN tracking coverage.


From Saturday, 06/06, through Tuesday, 06/09, there were no changes in spacecraft configuration.


On Wednesday, 06/10, 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 Thursday, 06/11, there were no changes to spacecraft configuration.


Upcoming events:


Activities scheduled for the week of 6/12 - 6/18 include: SSR FSW Partition Maintenance and Bus Heater
Power On (both activities on 6/12), SSR Pointer Reset and Spacecraft IVP Active Vector Update (both on
6/17).


DSN Coverage:


Over the past week Cassini had 2 scheduled DSN tracks. The track occurring on 6/05 was for telemetry and
command; the track occurring on 6/09 was dedicated to Navigation. In the coming week there will be 3 DSN
track periods.



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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