From: Jet Propulsion Laboratory
Posted: Friday, March 12, 2010
The most recent spacecraft telemetry was acquired on Mar. 9 from the Deep Space Network tracking complex at Madrid, Spain. 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, March 3 (DOY 062)
Non-targeted flybys of Pan, Calypso, and Helene occurred today.
A day after the targeted flyby of Rhea, Cassini made its closest approach of the mission to Helene at about 1,800 kilometers. On approach the Visible and Infrared Mapping Spectrometer (VIMS) took measurements that will help scientists analyze Helene's surface composition and understand if it is coated with particles from the E ring. Using a "skeet shoot"-style observation, the Imaging Science Subsystem (ISS) captured close-ups of the moon. Scientists hope these new views may reveal clues about Helene's past, including how it was gravitationally captured by the larger moon Dione, and whether a collision was part of its past. For more information link to: http://saturn.jpl.nasa.gov/mission/flybys/helene20100303/ .
Update: Playback for Rhea and the non-targeted Helene observation was nominal until rain in Canberra Saturday and Sunday, Mar. 6 and 7, knocked out some telemetry. A total of 285 minutes was affected, full loss of telemetry for 225 minutes, and degraded data for 60 minutes.
The main engine cover was opened today, completing the 58th in-flight cycle for the cover.
Thursday, March 4 (DOY 063)
This week ISS performed an Iapetus observation, and imaged Helene in a "skeet shoot"-style observation. This will be the best Helene observation of the mission. The term "skeet shoot" is used in relation to a specific imaging technique. On Earth, skeet shooting is an outdoor shotgun sport that simulates shooting game birds in flight. The skill in successfully hitting the moving clay target is for the shooter to point a little ahead of the clay pigeon, and match its angular velocity when the trigger is pulled. The clay pigeon then ideally passes into the bird shot when the shot arrives at its destination in the path of the moving target. Borrowing from the firearms sport, the trick was to turn the spacecraft in the same direction as Helene's' path across the sky. The plan was to match Helene's angular velocity at the exact times when it passed into the camera's field of view.
Continuing with science observations, the Cassini Plasma Spectrometer led the Magnetospheric and Plasma Science (MAPS) instruments in a long dusk magnetosphere observation, VIMS performed E and G ring observations, the Magnetometer performed a calibration roll, and the Ultraviolet Imaging Spectrograph (UVIS) performed mosaic scans of Saturn's magnetosphere. A total of 64 hours of the MAG orbit 127/128-segment time has been allocated to UVIS mosaic scans between DOY 066 and 075. These observations scanned the Saturn system between -10 and +10Rs. The activity started at Saturn center with the UVIS slit aligned along the Saturn spin axis. The spacecraft then slewed about its Z-axis until the UVIS field of view was 10Rs from Saturn center. UVIS began data capture, stared for 125.0 seconds, and then stopped data capture. The spacecraft was then turned by 2mrad, and UVIS repeated its observation pattern. These steps proceeded across the Saturn system. During the segments the observation will cover a distance of 20Rs, and repeat this pattern many times.
Planetary scientists have been puzzling for years over the honeycomb patterns and flat valleys with squiggly edges evident in radar images of Saturn's moon Titan. Now, working with a volunteer researcher who has put his own spin on data from Cassini, they have found some recognizable analogies to a type of spectacular terrain on Earth known as karst topography. A poster session today at the Lunar and Planetary Science Conference in The Woodlands, Texas, displays their work. For the full text of this article link to: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20100304/ .
Friday, March 5 (DOY 064)
Two proposals for outreach workshops have been accepted for presentation at the California Science Education Conference in Sacramento, Calif., in October of this year. One workshop is on "Our Solar System Through the Eyes of Scientists" and the other is on "Reading, Writing & Rings." These workshops are in addition to a 3-hour short course on "Our Solar System Through the Eyes of Scientists" which has already been accepted. "Our Solar System Through the Eyes of Scientists" is a spin-off of "Reading, Writing & Rings," so it is significant that both of these science and language arts K-4 and K-6 educational programs are being acknowledged and invited to be presented to California science teachers.
The website UnmannedSpaceflight.com has awarded Cassini Outreach the third UMSF Opportunity Award, given for excellence in public engagement. The team was praised for taking the public to Saturn with the release of all raw images taken by Cassini, and in recognition of its various educational activities, including Reading, Writing & Rings, and Scientist for a Day. For more information on this award link to: http://www.umsfawards.com/?p=93.
Monday, March 8 (DOY 067)
The Science Forum for S61 was held today. Topics included an overview of science planned for this sequence followed by highlights, unique activities, and highest priority observations as described by the Target Working Team (TWT) and Orbiter Science Team (OST) leads, with comments from the Investigation Scientists and other instrument team representatives.
TWT and OST integrated products for S63, covering orbits 137 through 139 in September and October 2010, were delivered today. The integrated products are in their final form and no re-integration is planned. The next step in sequence development, Science Operations Plan (SOP) implementation, will kick off on Mar. 22. A Science Planning Attitude Strategy Spreadsheet will be delivered to the instrument teams on Mar. 10 so that they can begin working on the pointing designs for this sequence. The final Cassini DSN station requests will be delivered to the DSN schedulers today.
The delivery dispersions to the Rhea flyby were such that returning to the reference trajectory with Orbit Trim Maneuver (OTM) 239 and OTM-240 was going to cost about 1.5 m/s over targeting directly to either Titan 67 or Dione 2. Science evaluated the two targeting options and selected the Dione targeting with the Titan conditions allowed to float free. With this strategy, OTM-239 is not required, so OTM-239 has been cancelled.
After cancellation of OTM-239, an initial analysis by Science Planning (SP) showed that three observations during the Titan 67 flyby would have large enough pointing errors to call for a live update. SP recommended that the update be performed for Titan, but deferred to the instrument teams for the Saturn live update. The Composite Infrared Spectrometer, ISS and VIMS are the only prime instruments during T67. All three teams have reviewed the analysis materials and confirmed that only Titan will require an update.
Tuesday, March 9 (DOY 068)
Science Planning and Uplink Operations hosted a kick-off meeting today for the handoff of the S60 background sequence product from the Science Operations Plan process (SOP) to the final process in sequence development, the Science and Sequence Update Process (SSUP). SSUP will last for approximately 10 weeks with S60 beginning execution on May 17. Upcoming events include the delivery of Sequence Change Requests (SCR) and review comments on Mar. 10, with an SCR approval meeting to be held on the 16th.
Recently Insider's Cassini featured an article on Uplink Operations. The activities of this team often figure prominently in the Weekly Significant Events report. On the development side, Sequence Leads are responsible for developing a final integrated, flyable sequence of commands, and then approve it to be sent to the spacecraft. On the downlink side, the leads respond to any alarms in telemetry, verify proper "clocking out" of the active sequence on board Cassini, and recover from anomalies, including restarting science instruments. They also build real-time commands, should it be necessary, and provide flight rule checks for the integrated sequence to be flown. For the full text of this article link to: http://saturn.jpl.nasa.gov/news/cassiniinsider/insider20100226/.
Cassini Outreach staffed an Outer Planets display at the Lunar and Planetary Sciences Conference last week. In all, 1500 attendees saw the display, and over 500 mission fact sheets, bookmarks and lithographs were distributed. This month's What's Up podcast is about Saturn, which is at opposition this month, and at its best viewing of the year from now through July. http://solarsystem.nasa.gov/news/whatsup-view.cfm?WUID=324.
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