Cassini Significant Events
8/20/08 - 8/26/08
The most recent spacecraft telemetry was acquired on Aug. 26 from the
Deep Space Network tracking complex at Goldstone, Calif. 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.
Thursday, Aug. 21 (DOY 234):
Imaging Science (ISS) spent eleven hours today searching for "spoke"
features in the rings. First detected during the Voyager flybys of
Saturn in the early eighties, the spokes are one of the great
mysteries of Saturn as they appear to come and go. The Composite
Infrared Spectrometer (CIRS) and Visual and Infrared Mapping
Spectrometer (VIMS) also participated in this observation.
Friday, Aug. 22 (DOY 235):
Orbit Trim Maneuver (OTM) #164 was performed today. This is the
cleanup maneuver after the Enceladus 4 encounter on Aug. 11. The
main engine burn began at 2:45 AM Pacific Time. Telemetry immediately
after the maneuver showed the burn duration was 81.2 seconds, giving
a delta-V of 13.5 m/s. All subsystems reported nominal performance
after the maneuver.
The next maneuver #164A is scheduled for Sept. 20. When the
reference trajectory was updated in 2007 for the Enceladus 3 and 4
flybys planned for 2008, it was determined that a maneuver needed to
be added between OTM-164 and OTM-165. Rather than renumbering the
entire suite of OTMs from that point on, and because it is desirable
to maintain the numbering convention where apoapsis maneuver numbers
are divisible by three, it was decided that adding the character "A"
to the number was the solution. For extended mission there have been
several "A" maneuvers added to the trajectory. Watch for them in the
coming months.
Sunday, Aug. 24 (DOY 237):
The main engine cover was closed today at the end of the OTM-164
backup window for potential dust hazards on Aug. 26, Sept. 2, and
Sept. 17.
Today the Cassini Infrared Spectrometer (CIRS) performed a ten-hour
observation of Saturn's atmosphere to measure the oxygen compounds
H2O and CO2 in Saturn's stratosphere as a function of latitude.
Monday, Aug. 25 (DOY 238):
The entire Optical Remote Sensing (ORS) suite of instruments
participated in a Saturn north pole campaign today. The campaign is
a series of concurrent observations of Saturn's north polar region.
After observing Saturn, the ORS instruments observed a stellar
occultation of a star called "gamCru" as it passed behind the rings
of Saturn. By monitoring the "flicker" of the star as the rings
obstruct it, scientists can learn more about ring structure.
Tuesday, Aug. 26 (DOY 239):
A non-targeted flyby of the satellite Atlas occurred today.
As the spacecraft passed through the auroral region of Saturn today,
the Magnetospheric and Plasma Science (MAPS) instruments captured
data on the electromagnetic and plasma environment in the hope of
learning more about the auroral processes on Saturn.
The Cassini Radio Science S43 orbit 82 rings chord occultation was
completed successfully today. The experiment was supported by
Madrid's DSS-63 with X- and S-band support, and DSS-55 with X- and
Ka-band support. This was the third in a family of four fast chord
occultations that probe the rings when the opening angle B is small,
about 5 to 7 degrees. The observation geometry complements in nature
earlier occultations conducted at larger B angles, providing valuable
information about the variability of ring structure and scattering
properties with ring viewing geometry.
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