Cassini Significant Event Report
For Week Ending 01/09/98
Significant Events input for 3 weeks from Friday 12/19 through Thursday 01/08.
(This is an expanded report covering events over the JPL holiday period.)
The Cassini spacecraft is in an excellent state of health and is operating
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)
The C5 sequence continues to execute onboard the spacecraft. C5
activities will be completed on Sunday, 1/18/98.
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 needed
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.
Spacecraft Activity Summary:
The 28-day Magnetospheric Imaging Instrument (MIMI) decontamination activity,
begun on 11/21, continued nominally, and ended on Friday, 12/19.
On Tuesday, 12/23, 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 Monday, 12/29, the Solid State Recorder (SSR) record and playback pointers
were reset, according to plan.
On Sunday, 01/04, the Solid State Recorder (SSR) record and playback pointers
were reset, according to plan.
On Thursday, 01/08, an Attitude and Articulation Control System (AACS) High
Water Mark housekeeping activity was performed on the spacecraft, as planned.
"High water marks" are maintained onboard the spacecraft for a number of AACS
measurements. These channels, which track maximum excursions for a given
measurement, are contained in the regular downlink telemetry stream and are
tracked on the ground to facilitate the assessment of subsystem health. These
channels are cleared approximately every two months (or more frequently when
dynamic spacecraft activities are scheduled, such as trajectory correction
maneuvers), maintaining good visibility into subsystem status.
Finally, on Thursday, the Cruise 6 Sequence was uplinked to the spacecraft.
This sequence will begin executing on Sunday, January 18, in the late afternoon
Upcoming spacecraft events:
Events for the week of 01/09 through 01/15 include: a reset of the SSR pointers
(01/10) and the first two of three parts of the periodic engineering maintenance
sequence (AACS Engine Gimbal Actuator (EGA) and Reaction Wheel Assembly (RWA)
Over the past 3 weeks Cassini had 7 DSN track periods (12/20 through 12/24, 01/
01, and 01/08). In the coming week, there will be one DSN pass - on Wednesday
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.