Cassini Significant Events 11/24/09 – 12/01/09

The most recent spacecraft telemetry was acquired on Dec. 1 from the Deep Space Network tracking complex at Goldstone, California. 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.

Tuesday, Nov. 24 (DOY 328)

A close-up image of ice jets erupting from the tiger stripes on Enceladus was Astronomy Picture of the Day today. Check it out at: http://antwrp.gsfc.nasa.gov/apod/ap091124.html

The topic at the Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference for November was "Science Highlights from Cassini's Ion and Neutral Mass Spectrometer." An audio recording and PDF of the presentation are available at: http://saturn.jpl.nasa.gov/video/products/MultimediaProductsCharm/

Wednesday, Nov. 25 (DOY 329)

An AACS Periodic Engineering Maintenance (PEM) occurred today. Performed every 90 days, this activity exercises the Engine Gimbal Actuators and the backup Reaction Wheel Assembly (RWA). In the RWA exercise, the wheel is commanded to +100 rpm, -100 rpm, 0 rpm, then turned off.

The moon Prometheus is seen whipping gossamer ice particles out of Saturn's F-ring in an image taken by the Cassini spacecraft on Aug. 21, 2009. The moon and the ring have eccentric, offset orbits, so Prometheus dips in and out of the F ring as it travels around Saturn. Its gravitational force drags the dust-sized particles at the edge of the F ring along for the ride. To view this image and the full description link to: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20091125/

Monday, Nov. 30 (DOY 334):

In a news release published today on the Cassini Website, scientists suggest that the eccentricity of Saturn's orbit around the sun may be responsible for the uneven distribution of lakes over the northern and southern polar regions of the planet's largest moon, Titan. A paper describing the theory appeared in the Nov. 29 advance online edition of Nature Geoscience. Like Earth and the other planets, Saturn's orbit is not perfectly circular, but is instead somewhat elliptical. Because of this, during its southern summer, Titan is about 12 percent closer to the sun than during the northern summer.
It is proposed that, in this orbital configuration, the difference between evaporation and precipitation is not equal in opposite seasons, which means there is a net transport of methane from south to north. This imbalance would lead to an accumulation of methane -- and hence the formation of many more lakes -- in the northern hemisphere. For the full text of the release link to: http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20091130/

Tuesday, Dec. 1 (DOY 335)

Science Operations Plan development for S58 was completed today with the hand off of all files and status to Uplink Operations and the kick off of the Science and Sequence Update Process, the final process in sequence development.

An encounter strategy meeting was held today to cover the period between Dec. 12 and Dec. 22, Titan flybys T63 and T64, and maneuvers 227-229.

A Y-thruster calibration took place on board the spacecraft today. AACS reported very good results, with Y-thrusters averaging 14.2 seconds of on time and Z-thrusters averaging 0.7 seconds on-time. This calibration was performed primarily for Navigation to measure any thruster imbalances.