Cassini Significant Events 12/19/07 - 12/25/07

December 28, 2007

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired on Tuesday, Dec. 25, from the Goldstone tracking complex. 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:

Wednesday, Dec. 19 (DOY 353):

The Cassini Radio Science (RSS) orbit 54 Saturn rings and atmospheric occultation observation was completed successfully today. The experiment was covered by Madrid's DSS-63 for S- and X-band support, and DSS-55 for X- and Ka-band support. Observations included the first chord ring occultation with inbound and outbound occultations on the same ring side, as well as ingress and egress ionospheric and atmospheric Saturn occultations.

The ring-opening angle of 6.6 degrees occurring at this time is the smallest so far in the prime mission. With the angle this small, the occultation will provide excellent sensitivity to ring structure of relatively small optical depth. The atmospheric occultations probe southern Saturn latitudes of about 16 and 68 degrees on the ingress and egress sides, respectively. The two are part of a campaign of occultations during the last year of the prime mission that probe low, mid, and high southern latitudes of Saturn, complementing several near-equatorial occultations earlier in the mission.

After the RSS observations were complete, the spacecraft transitioned from reaction wheel to thruster control for the duration of a Radio and Plasma Wave Science (RPWS) Whistler observation.

Thursday, Dec. 20 (DOY 354):

On Dec. 20, Cassini flew by Titan at an altitude of 970 km and a speed of 6.3 km/sec for the T39 targeted encounter. This was the last Titan flyby under 1000 km in the prime mission. Scientific observations for T39 included RADAR obtaining high resolution Synthetic Aperture RADAR (SAR) coverage of the south-pole region at closest approach, and reaching to around 70 degrees. The Composite Infrared Spectrometer (CIRS) measured stratospheric temperatures as well as obtained limb measurements and vertical temperature and compositional profiles. Imaging Science (ISS) collected a full disk color sequence at 1.4 km/pixel, and performed low phase angle measurements of Rhea. Finally, the Visual and Infrared Mapping Spectrometer (VIMS) mapped the mid-latitude regions at small solar phase angles, monitored cloud motions on a global scale, and monitored the probe landing site. For more details on this flyby, link to:

Friday, Dec. 21 (DOY 355):

Thanks to an accurate delivery to the Titan 39 flyby, Orbit Trim Maneuver (OTM) #140, due to execute on Dec. 23, has been determined to have a magnitude of 0.4 mm/s, and delta V cost of cancellation of only 1.1 mm/sec. Based on this, the decision has been made to cancel OTM 140.

After today, the flight team will begin the annual two-week break from sequence development. The decision was made early on in the mission to pause development at this time due to the number of individuals taking time off for the holidays, and the differences in holiday schedules between the US and Europe. Work will begin again on S37-S41 on Jan. 7.

Monday, Dec. 24 (DOY 358)

An image taken from edge-on with the ring plane, and containing four of Saturn's attendant moons, Tethys, Enceladus, Hyperion and Epimetheus, is available for viewing at:

Today marks the 3rd anniversary of the release of the Huygens Probe to begin the journey to Titan on Christmas Eve, 2004.