Cassini Significant Events 07/15/09 – 07/21/09

The most recent spacecraft telemetry was acquired on July 21 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/operations/present-position.cfm .

Wednesday, July 15 (DOY 196)

An encounter strategy meeting was held today to cover the period between
July 24 and August 9, Titan flybys T59 and T60, and maneuvers 109-111.

The Target Working Team (TWT)/ Orbiter Science Team (OST) integrated
products for S57, covering orbits 125 through 127, from January 2010 through
March 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
July 29. Between now and then, the instrument teams will be working on
pointing designs for the sequence. TWT/OST teams deliver integrated sequence
products for the extended mission about every five weeks.

Thursday, July 16 (DOY 197):

Science today included Imaging Science (ISS) observations of the retinue of
small moons following Saturn, and the Magnetospheric and Plasma Science
(MAPS) instruments' study of the solar wind boundary of Saturn’s
magnetosphere. This was followed by a Composite Infrared Spectrometer (CIRS)
observation designed to study the polarization of light reflected from
Saturn’s rings at far infrared wavelengths.

Today sequence leads uplinked seven Instrument Expanded Block (IEB) files to
the spacecraft in support of S52. The remaining two IEBs will go up on
Saturday, and the background sequence will go up on Monday. The S52
sequence will begin execution on Thursday, July 23.

Friday, July 17 (DOY 198):

Today the Visual and Infrared Mapping Spectrometer (VIMS) trained its
sensors on Antares for calibration purposes. Periodic calibration is
critical to the successful interpretation of VIMS and other instrument
observations. The calibration was followed by another MAPS study of the
boundary region of the magnetosphere, and Navigation imaging. At the end of
the day the Ultraviolet Imaging Spectrograph (UVIS) turned towards
Sagittarius to watch it slip behind the rings of Saturn.

Orbit Trim Maneuver (OTM) #207 was performed today. This was the apoapsis
maneuver setting up for the Titan 59 encounter on July 23. The Reaction
Control Subsystem (RCS) burn began at 10:15 AM PDT. Telemetry immediately
after the maneuver showed the burn duration was 24.13 seconds, giving a
delta-V of 32.68 mm/s. All subsystems reported nominal performance after the
maneuver.

Saturday, July 18 (DOY 199):

A nearly edge-on telescopic view of Saturn's rings was offered to 100
attendees at a star party in Warner Springs, CA, on July 18. Cassini
Outreach members participated in the event.

Monday, July 20 (DOY 201):

After the kick off meeting today for the DOY 207 Live Inertial Vector
Propagator (IVP) update, instrument teams reviewed the impact if the update
were cancelled. It turned out that CIRS would have lost part of their
observation and ISS would not have gotten their images of the plumes along
the limb of Enceladus. As a result, the team will proceed with the update
and vectors for both Saturn and Janus for ISS and VIMS will be updated.
Final files will be delivered on July 23 with an approval meeting held on
July 24. The files will be uplinked that same day and will execute on
Sunday, July 26.

Tuesday, July 21 (DOY 202):

Thanks to accurate orbit determination and execution of OTMs 206 and 207,
the maneuver planned to correct the delivery dispersions for the Titan 59
flyby was smaller than the permissible minimum RCS maneuver magnitude.
Execution of OTM-208 would have required the addition of a time of closest
approach bias to increase the magnitude to an achievable level. Science
planning has evaluated both the maneuver and no-maneuver cases and found
both to be acceptable. Cancellation reduced the predicted down stream
delta-V by about 90 mm/sec. Therefore OTM 208, originally scheduled to
execute today, was cancelled.