Cassini Significant Events 09/08/10 - 09/14/10
The most recent spacecraft telemetry was acquired on Sept. 14 from
the Deep Space Network tracking complex at Canberra, Australia. 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/mission/presentposition/.
Wednesday, Sept. 8 (DOY 251)
Yesterday the Cosmic Dust Analyzer (CDA) team performed a 15-hour
decontamination of the instrument's detector. Decontaminations occur
every few months and are part of normal CDA instrument maintenance. The
decontamination activity went well and the instrument is functioning
normally.
Last Friday's Orbit Trim Maneuver (OTM) #261 was the 200th maneuver
performed by the spacecraft since its arrival at Saturn. About 60 planned
maneuvers have been able to be cancelled.
Target Working Team and Orbiter Science Team integrated products for S67,
covering orbits 146 and 147 from March 2011 through April 2011, were
delivered today. The integrated products are in their final form and no
re-integration is planned. The Sequence Implementation Process will kick
off on Sept. 27. The instrument teams are currently working on the
pointing designs for this sequence.
Thursday, Sept. 9 (DOY 252)
An encounter strategy meeting was held today to cover the period
between Sept. 24 and Nov. 11, Titan flybys T72 and T73, and maneuvers
263-265.
Friday, Sept. 10 (DOY 253)
This week the Composite Infrared Spectrometer (CIRS) performed
several observations measuring oxygen compounds in Saturn's stratosphere.
The Ultraviolet Imaging Spectrograph (UVIS) had a nine hour observation
scanning Saturn's atmosphere in Far-Ultraviolet wavelengths; its
ultraviolet detectors scanned slowly to create spectral images. The
Magnetometer (MAG) instrument performed a calibration of its sensors by
rolling the spacecraft.
These calibrations are performed every 15-20 days, and serve to insure
the accuracy of the magnetometer. Imaging Science (ISS) conducted an
observation of tiny moons orbiting Saturn, a four hour observation of
Hyrrokkin, and took images of Titan as part of the Titan Monitoring
campaign. A joint observation took place between the Visual and Infrared
Mapping Spectrometer (VIMS) and ISS to measure Saturn's winds.
Monday, Sept. 13 (DOY 256)
An RWA rest period took place today. During rest periods, the
reaction wheels are turned off for a few hours then turned back on to
allow the lubricant in the reaction wheels to be re-distributed
throughout the bearing assembly. Rest periods were recommended by
consultants from The Aerospace Corporation as a means to ameliorate
concerns over increasing friction levels in the bearings. They will be
implemented approximately every twenty days; the last time this activity
occurred was on Aug. 20.
Commands were uplinked to the spacecraft today to clear the recent Solid
State Power Switch (SSPS) trip. There was a memory read out performed
before and after the SSPS trip counter was reset.
The Reaction Wheel Assembly revolution counters were reset to 0
revolutions today. The reaction wheels each have a counter that counts
revolutions.
The counters are reset whenever one of the counters gets close to the max
value; otherwise, it will reach the max value and just stay there. This
enables an accurate tracking of total revolutions for each wheel over the
course of the mission.
Tuesday, Sept. 14 (DOY 257)
At the Mission Planning Forum today the topic was the Titan-70 (T70)
post flyby attitude control results and corresponding atmospheric density
estimate. The T70 flyby on June 20, 2010, was the lowest altitude flyby
of Titan ever performed by the Cassini spacecraft. The predicted set of
two Z-facing thrusters had the highest activity among the thrusters, as
expected. However, the duty cycles of these two thrusters were higher
than expected, although well within available margins. Further analysis
of the T70 data to explain the reason for the higher-than-expected
thruster activities is still ongoing. The spacecraft's health and safety
status before, during, and after the Titan-70 flyby was nominal and there
was no fault protection activity.
Port 2 products were due today as part of the S66 Sequence Implementation
Process (SIP). The products will be merged tomorrow and sent out to the
flight team for review.
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