News | December 8, 2010
Cassini Significant Events 12/01/10 - 12/07/10
The most recent spacecraft telemetry was acquired on Dec. 7 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, Dec. 1 (DOY 335)
Orbit Trim Maneuver (OTM) #269 was performed today. This was the clean-up maneuver following the Enceladus encounter on Nov. 30. The Reaction Control Subsystem (RCS) burn began at 3:45 PM PST. Telemetry immediately after the maneuver showed a burn duration of 146.87 seconds, giving a delta-V of 0.162 m/s. This maneuver was executed during the backup window to avoid low Reaction Wheel Assembly (RWA) speeds and to take advantage of a lower delta-V cost compared to using the prime window. All subsystems reported nominal performance after the maneuver.
Commands to normalize the Attitude and Articulation Control Subsystem (AACS), Cosmic Dust Analyzer (CDA), and Composite Infrared Spectrometer (CIRS) flight software loads successfully went through final Integrated Test Laboratory (ITL) testing today.
The main engine (ME) cover was opened today, the 62nd in-flight cycle.Telemetry continues to show nominal operations for the cover. The AACS secondary safe table value was restored to 0 degrees following the E-12 flyby.
An in-reach presentation was given today by the Cassini Deputy Project Scientist covering the Cassini science highlights of the August-October 2010 quarter, including results from the disciplines of fields-and-particles, icy satellites, Saturn, Titan and the rings.
A feature story called "Cassini Returns Images of Bright Jets at Enceladus" is available on the Cassini web site. The Cassini spacecraft passed near the surface of Saturn's moon Enceladus on Nov. 30. Though closest approach occurred about 48 kilometers above the surface over the moon's northern hemisphere, the spacecraft also captured shadowy images of the tortured south polar terrain and the brilliant jets that spray out from it. For more information on this subject and raw images, link to:
Thursday, Dec. 2 (DOY 336)
This week's science observations included six hours of the Ultraviolet Imaging Spectrograph (UVIS) mapping the ultraviolet albedo of Enceladus as a function of longitude and phase angle. The Composite Infrared Spectrometer (CIRS), Imaging Science (ISS), and the Visual and Infrared Mapping Spectrometer (VIMS) collected more Enceladus data as riders with the UVIS observations. ISS took over for almost five hours to search around the Rhea L4 Lagrange point for new satellites. The Magnetometer (MAG) completed a 24 hour rolling activity to collect data for the suite of Magnetospheric and Plasma Science (MAPS) instruments, and performed a 13.5 hour calibration while rolling about the X-axis of the spacecraft. ISS performed several observations in its Satellite Orbit Campaign, completed a 13 hour edge-on observation of the E ring, and observed the transit of Dione across Tethys for orbit determination purposes. CIRS and VIMS performed a 10 hour observation to measure oxygen compounds in Saturn's stratosphere. ISS, CIRS and VIMS performed another observation in the Titan monitoring campaign.
The Downlink Ground System (DGS) team presented the Distributed Object Manager (DOM) to Network File System (NFS) transition plan at an Instrument Operations Working Group (IOWG) meeting today. A target delivery date of Feb. 22, 2011, has been tentatively scheduled for the transition of the DOM to NFS into the operations environment.
Friday, Dec. 3 (DOY 337)
On Tuesday, Nov. 30, Cassini Radio Science (RSS) completed the Rev 141 Enceladus (E-12) gravity observation. The objective of the experiment was to detect a diapir under the south pole and determine the gravity field of Enceladus. Detecting a diapir requires at least three flybys -- E-12 was the second RSS Enceladus gravity flyby, the first was E-9 back in April, and the next is E-19 in May 2012. The observation consisted of three 3-hour segments -- inbound, closest approach, and outbound, and was covered by beam wave guide (BWG) antennas at all three DSN complexes. Enceladus closest approach was at 334/1318 ERT over DSS-26.
Monday, Dec. 6 (DOY 340)
An RWA rest period took place today. During rest periods, the reaction wheels are turned off for a few hours, then turned back on to allow the lubricant in the reaction wheels to be re-distributed throughout the bearing assembly. Rest periods are being implemented regularly, approximately every twenty days.
Tuesday, Dec. 7 (DOY 341)
At the Mission Planning Forum this week, Mission Planning gave a presentation on consumables status. The topic: "Review of predicted and actual usage for S62 - S63 and an update to the hydrazine and Delta-V budgets." A consumables status is provided on a regular basis so the project can maintain cognizance of propellant usage and end of mission margins.
Today a panel of Cassini scientists answered questions from students who participated in the Cassini Scientist for a Day contest. The event was broadcast live via a Ustream video stream. The one-hour show started at 10 a.m. Pacific Time.