Significant Event Report for Week Ending 6/19/1998

Cassini Significant Event Report

For Week Ending 06/19/98

Spacecraft Status:

The most recent Spacecraft status is from the DSN tracking pass on Wednesday, 06/17, 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.

Spacecraft Activity Summary:

On Friday, 06/12, a maintenance activity was performed on the SSR Flight Software Partitions. This activity,
performed approximately every 2 weeks, repairs any SSR double bit errors (DBEs) which have occurred in
the code-containing portions of the Flight Software partitions during the preceding period.

Also on Friday, commands were sent to turn the bus heaters on to slowly warm up the propellant system. The
results of this characterization activity will be incorporated in the design of the test maneuver to be conducted
in November.

On Wednesday, 06/17, 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.

Also on Wednesday, the Attitude and Articulation Control Subsystem's active vector was updated. This is a
routine activity that is needed periodically to maintain proper spacecraft orientation with respect to the sun.

Upcoming events:

Activities scheduled for the week of 06/19 - 06/25 include: SSR Pointer Reset, Switch to Low Gain Antenna
1, SSR FSW Partition Maintenance, and AACS Attitude Estimator Memory Readout, all on 06/24.

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.

Media Relations Office

Jet Propulsion Laboratory

California Institute of
Technology

National Aeronautics and Space
Administration

Pasadena, Calif. 91109.
Telephone (818) 354-5011