Cassini Significant Events 08/26/09 - 09/01/09
The most recent spacecraft telemetry was acquired on Sept. 1 from the
Deep Space Network tracking complex at Goldstone, California. The Cassini
spacecraft is in an excellent state of health and all subsystems are
operating normally. Information on the present position and speed of the
Cassini spacecraft may be found on the "Present Position" page
at:
http://saturn.jpl.nasa.gov/operations/present-position.cfm .
Wednesday, Aug. 26 (DOY 238):
A two-day Titan Science Workshop held at the California Institute of
Technology began today. Topics on the agenda included presentations and
discussions of Titan¹s gravity, hypsometry, spin rate, temporal changes,
surface composition, surface temperature, sea-shoreline elevations, lake
distribution, composition and shape, and future plans for observations in
the proposed Cassini Extended Extended mission.
This week Cassini science observations included Visual and Infrared
Mapping Spectrometer (VIMS) high phase and low phase mosaics of the rings
and an occultation of alpOri by the F - D rings. The Ultraviolet Imaging
Spectrograph (UVIS) performed an additional low incidence angle
occultation. Imaging Science (ISS) imaged Janus in the ring shadow,
observed a Telesto close flyby at ~24,700 km and 86 deg phase at closest
approach, performed a Titan cloud monitoring activity, looked for shadows
of vertical features in the rings, performed a 9.5h radial scan of the
main rings, and created a lit face, high phase movie in search of ring
spokes. The Composite Infrared Spectrometer (CIRS) also created a
low-phase thermal map of the rings and performed a 6h equinox baseline
observation. Finally both the Cassini Plasma Spectrometer (CAPS) and
Magnetospheric and Plasma Science (MAPS) suite of instruments each
performed a 2-hour survey.
Thursday, Aug. 27 (DOY 239):
Non-targeted flybys of Pallene and Telesto occurred today.
In the Significant Events Report for Tuesday, Aug. 18, it was reported
that an anomaly occurred in the Spacecraft Office (SCO) Integrated Test
Lab (ITL) between a CDS hardware interface and the support equipment.
Today SCO reported that the ITL is back up and functioning in dual string
mode with the CDS flight spare and engineering model computers. The
problem was isolated to a support equipment interface board. The
functionally equivalent board was removed from CDS Test Bed 1 and moved
to ITL Test Bed 3. SCO is now working on having the problem board
refurbished.
Friday, Aug. 28 (DOY 240):
At 6:30 PM, Pacific Daylight Time, JPL employees were notified that
due to brush fires in the area, the primary Oak Grove site would be
closed to all but essential personnel over the weekend as a precautionary
measure. In this case for Cassini, essential personnel included
individuals needed for the successful execution of Orbit Trim Maneuver
(OTM)-215 on Saturday morning.
Saturday, Aug. 29 (DOY 241):
Due to ongoing issues with the LCROSS spacecraft, it was requested
that Cassini give up the beginning of two DSN tracks on DOY 241 and 243.
For DOY 241, DSN schedulers were able to obtain a short DSS-55 track to
maintain the full OTM-215 uplink window. On DOY-243, the decision was
made - with the concurrence of project management - to accept the science
data loss. This will result in approximately 45 MB of data that will not
be seen on the ground due to the loss of DSS-65 track time.
Orbit Trim Maneuver (OTM) #215 was performed today. This is the cleanup
maneuver from the Titan 61 encounter on Aug. 24. The main engine burn
began at 7:45 AM PDT. Telemetry immediately after the maneuver showed the
burn duration was 2.97 seconds, giving a delta-V of 0.50 m/s. All
subsystems reported nominal performance after the maneuver.
Monday, Aug. 31 (DOY 243):
JPL Update Sunday, August 30, 2009, 4:45 pm Fire conditions around
JPL have continued to improve throughout the day, and the Station Fire no
longer threatens the facility. However, there has been heavy smoke in the
area. To ensure acceptable air quality for the safety of employees, the
Laboratory was closed on Monday except for mission-critical personnel. A
decision regarding reporting to work on Tuesday will be made by Monday
afternoon.
Tuesday, Sept. 1 (DOY 244):
JPL resumed normal operations at 0600 hours Tuesday, September
1.
Science Planning handed over S55 sequence development to Uplink
Operations today at the Science and Sequence Update Process (SSUP)
kickoff meeting. SSUP takes approximately 10 weeks and is the final
sequence development process just prior to uplink and execution of the
background sequence and all related products. The first two weeks of DSN
allocation beginning on Nov. 13 have been negotiated. S55 DSN allocations
should be finalized by Sept. 9.
An image titled ³Shadows of Saturn at Equinox² is Astronomy Picture of
the Day today. To view the image and caption link to:
http://antwrp.gsfc.nasa.gov/apod/ap090901.html
An AACS Periodic Engineering Maintenance (PEM) occurred today. Performed
every 90 days, this activity exercises the main engine gimbal actuators,
the backup Reaction Wheel Assembly wheel, and scrubs some portions of
memory. In the RWA exercise, the wheel is commanded to +100 rpm, -100
rpm, 0 rpm, then turned off.
The Science Forum for S57 was held today. Topics included an overview of
science planned for this sequence followed by highlights/unique/highest
priority observations provided by the Target Working Teams and Orbiter
Science Team leads, with comments from the Investigation Scientists and
other instrument team representatives.
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