Cassini Significant Events 05/05/10 - 05/11/10

[Cassini <Cassini@xxxxxxxxxxxx>]

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. For more information on both missions link to the
following:
http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=2003-019A
http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=PLANET-C

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:
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20100511/



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