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Cassini Significant Events 05/05/10 – 05/11/10

The most recent spacecraft telemetry was acquired on May 11 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, May 5 (DOY 125)

Science activities for this week included long duration Composite Infrared Spectrometer (CIRS) mid-infrared observations of Saturn. The purpose of these observations was to profile the temperature of the upper troposphere and tropopause of Saturn in various latitude regions. In addition, CIRS measured Saturn oxygen compounds as a function of latitude and performed long term monitoring of infrared stars. Imaging Science (ISS), CIRS, and the Ultraviolet Imaging Spectrograph (UVIS) captured the long-term features of the atmosphere of Titan as part of an on-going Titan Monitoring Campaign.

ISS also performed observations of Iapetus and Bebhionn. Due to the moon's small apparent size, ISS was only able to characterize the light signature of Bebhionn as it rotated against the darkness of space by pointing to the object for more than 11 hours. Finally, the Cassini Plasma Spectrometer (CAPS) performed several observations of Saturn's magnetosphere.

Thursday, May 6 (DOY 126)

The decision was made at a preliminary Navigation review meeting for Orbit Trim Maneuver (OTM) #246 to target to Titan rather than Enceladus in the upcoming dual flybys on May 18 and 19. There is an additional delta V cost of 4.3 m/sec by targeting Enceladus, and the Enceladus 10 plume occultation will be still be realized by the Titan 68 targeting. A decision was also made to perform an early OTM command file uplink to ensure the maneuver goes off on the prime pass, as the backup option is worse for E10.

UPDATE: The maneuver was successfully uplinked over a Madrid pass on May 8.

Sunday, May 9 (DOY 129)

Sequence Leads for S60 have begun uplinking the Instrument Expanded Block (IEB) files in support of that sequence. IEBs for ISS, the Visual and Infrared Mapping Spectrometer (VIMS), CIRS, the Ion and Neutral Mass Spectrometer, UVIS, and CAPS were sent today. Any remaining files will be sent next Wednesday, and the background sequence will follow on Thursday.

Monday, May 10 (DOY 130)

A Version 4 DSN station allocation file for S60 was delivered on April. 1 with all days fully negotiated. Now the sequence leads have received Planet-C contingency launch proposals for DOY 140, 141, 143, 145 and 146, and additional MUSES-C proposals for DOY 145 and 147. The following is what happens when it is necessary to re-plan DSN coverage for an executing sequence in the case of a launch contingency or anomaly. Kudos to the DSN, Cassini, and the Mars Missions for their efforts.
* The DOY 140 DSS-34 track will have the Beginning of Track (BOT) changed from 0505 to 1045.
* The Mars Reconnaissance Orbiter and Mars Exploration Rover projects have agreed to let us have DSS-43 from 0800 to 1115 for Cassini Radio Science (RSS). Leads are waiting for Mars Odyssey to weigh in.
* The DOY 141 change involves the loss of the entire DSS-15 track but DSS-26 will be swapped in for that time and a real-time TLM mode overlay file will be built.
* The DSS-34 track on DOY 143 is the OTM-248 prime window and its loss would have serious mission consequences beyond the loss of science. An alternative is in work.
* For DOY 145 the DSS-34 BOT will change from 0515 to 0945 ­ Cassini has asked for DSS-43 from 0515 to 0855 and recover most of the track if the pass is given to Planet-C.
* DOY 146 involves a DSS-34 BOT change from 0730 to 0945. ­This affects the RSS Ultra Stable Oscillator characterization, Radio Frequency Instrument Subsystem Periodic Instrument Maintenance, and receipt of ranging data. A proposal for using DSS-43 from 0730 BOT to 1250 End of Track (EOT) has been made.
* Working on MUSES-C proposals now for DOY 145 and 147. Real-time commands will only be built in advance for DOY 140 and 141 due to downlink of Titan 68 flyby data. Muses-C, renamed Hayabusa, is Japan¹s asteroid sample return mission with the return scheduled for June 13 of this year.

Planet-C is a Venus Orbiter also out of the Japanese Space Agency with a scheduled launch date of DOY-137, hence the contingency planning for DOY 140-146.

Tuesday, May 11 (DOY 131)

A close-up image of Herschel Crater on Mimas was Astronomy Picture of the Day today. Check it out at: http://antwrp.gsfc.nasa.gov/apod/ap100511.html

Real-time commands were sent to the spacecraft today, planned to execute on Friday, May 14, for ISS absolute timed loading of S60 IEBs from the SSR. Normally IEBs are loaded on or about the first day of a new sequence, in this case May 17. The early uplink for ISS is a precautionary measure to avoid the possibility of losing unique icy satellite science data planned early in S60.

Orbit Trim Maneuver (OTM) #246 was performed today. This was the apoapsis maneuver setting up for the Enceladus 10 and Titan 68 encounters on May 18 and 19. The main engine burn began at 5:14 AM PDT. Telemetry immediately after the maneuver showed a burn duration of 51.55 seconds, giving a delta-V of 8.88 m/s. All subsystems reported nominal performance after the maneuver.

An encounter strategy meeting was held today to cover the period between May 20 and June 5, Titan flybys T68 and T69, and maneuvers 248-250. This is another 16-day orbit with three maneuvers in 11 days.

It appears that flash flooding has paved streambeds in the Xanadu region of Titan with thousands of sparkling crystal balls of ice. By analyzing the way the terrain scatters radar beams, scientists deduce that the spheres measure at least a few centimeters and maybe up to a couple of meters in diameter. The spheres likely originated as part of water-ice bedrock in higher terrain in Xanadu. For the full release link to: