Дата: 14 апреля 1998 (1998-04-14)
От: Alexander Bondugin
Тема: Cassini Update - April 10, 1998
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CASSINI SIGNIFICANT EVENTS FOR
WEEK ENDING 04/10/98
The Cassini spacecraft is presently traveling at a speed of approximately
141,000 kilometers/hour (~88,000 mph) relative to the sun and has traveled
approximately 485 million kilometers (~300 million miles) since launch on
October 15, 1997.
The most recent Spacecraft status is from the DSN tracking pass on
Thursday, 04/09, over Canberra. The Cassini spacecraft is in an excellent
state of health and is executing the C7 sequence nominally.
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 except during the Probe Checkout #2
data playback over specially requested 70m passes.
Spacecraft Activity Summary:
On Friday , 04/03, the third of seven sequenced data playbacks occurred
for Huygens Probe Checkout #2. The Probe checkout activity occurs
approximately every 6 months. The series of data playbacks from the SSR
will provide detailed information on the results of the checkout.
On Saturday, 04/04, the fourth data playback occurred for Probe Checkout #2.
On Sunday, 04/05, the fifth data playback occurred for Probe Checkout #2.
On Monday, 04/06, 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. Additionally, the sixth data playback occurred
for Probe Checkout #2.
On Tuesday, 04/07, the seventh data playback occurred for Probe Checkout #2.
On Wednesday, 04/08, a partition copy maintenance activity was performed
to fix two double bit errors that are not in code-containing portions of
the SSR Flight Software Partitions.
Also on Wednesday, a mini-sequence to perform an eighth data playback for
Probe Checkout #2 was uplinked. This playback was requested by the Huygens
Probe Operations Centre to assist in the ongoing evaluation of the drop in
the Probe Umbilical AGC measurements. The playback occurred on Thursday,
04/09, and returns the 10 seconds out of each minute of recorded Probe
telemetry for that part of the Checkout data that has not already been
ESA has formed a team to examine the umbilical AGC data reported last
The team will meet on 4/16.
Activities scheduled for the week of 4/10 - 4/16 include:
Maintenance (4/10), an SSR pointer reset (4/11),
SSR Flight Software Partition
Maintenance (4/14), an SSR pointer reset (4/16),
and Periodic Instrument Maintenance (4/16 into 4/17).
Over the past week Cassini had 13 scheduled DSN tracks occurring from
04/03 through 4/09. In the coming week there will be 9 DSN passes.
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