NASA 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.
