Cassini Significant Events 10/24/07 - 10/30/07

November 1, 2007

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired on Tuesday, Oct. 30, 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, Oct. 24 (DOY 297):

This week the Ultraviolet Imaging Spectrograph (UVIS) performed a special stellar occultation observation of the Enceladus plume that was negotiated into the sequence at the "last minute". In sequence planning terms, this means months rather than years. The line-of-sight from Cassini to the star cut through the Enceladus plume about 16 km above the surface of Enceladus.

Additional science observations included the Visual and Infrared Mapping Spectrometer (VIMS) performing ring observations, Imaging Science Subsystem (ISS) continuation of a satellite orbit determination campaign, and spectrophotometry / phase coverage of Enceladus, Tethys, Mimas, Rhea and Dione, and Composite Infrared Spectrometer (CIRS) observations to determine Saturnian upper troposphere and tropopause temperature with spatial resolution of about two degrees of latitude and longitude.

As reported in the journal Nature, according to a new study led by Cassini scientists at the University of Colorado at Boulder, a narrow belt harboring moonlets as large as football stadiums discovered in the outermost ring of Saturn is likely the result of a larger moon shattered by a wayward asteroid or comet eons ago. Images revealed a series of eight propeller-shaped "wakes" in a thin belt of the outermost "A" ring, indicating the presence of corresponding moonlets. A link to this story can be found at:

A Cassini high-resolution mosaic of the rings of Saturn is Astronomy Picture of the Day today.

Thursday, Oct. 25 (DOY 298):

Cassini flight team members from the Science Planning Team assisted JPL Educational Affairs in a Planetary and Space Science Career Night at JPL. These events are held periodically and introduce area middle and high school students to different career opportunities in space and planetary science. At the same time, Outreach was giving a presentation on Saturn's moons using Cassini education materials at the California Science Teachers' Association convention in Long Beach, California.

The Aftermarket Process for the S40 sequence, orbits 65-70, began today. This 5-week process will address proposed changes that require re-integration of the segments contained in the S40 sequence.  The aftermarket process for S41, the last sequence in the prime mission, will begin on Dec. 4.

Sequence leads began uplinking instrument expanded block (IEB) files for S35. The remaining IEBs will be sent up tomorrow with the background sequence going up on Sunday night. S35 begins execution on Oct. 31.

Friday, Oct. 26 (DOY 299):

The AACS quarterly friction test for the prime reaction wheels (RWA) number 1, 2 and 4 was completed today. In this test, the RWAs are spun up to 900 rpm in both the clockwise and counterclockwise directions and timed as they are allowed to spin down to 0 rpm. Results from the test were not significantly different from those of previous tests.

Sunday, Oct. 28 (DOY 301):

A test of the backup RWA, number 3, was then performed on Sunday, Oct. 28. This test is performed twice a year. The backup wheel is spun up to 600 rpm in both directions and timed as it is allowed to run down to zero. Results also showed no significant changes compared to the last test performed April 16, 2007.

Monday, Oct. 29 (DOY 302)

All teams made their deliveries for the preliminary port as part of the S38 Science Operations Plan Update (SOPU) process. Science Planning is currently merging the instrument files and preparing to deliver review comments back to the teams.

An end-to-end dry run in the Integrated Test Laboratory for the AACS version A8.7.6 flight software is planned for Oct. 29-31. Uplink of this software is planned for Jan. 8-13, 2008, and will update the default thruster magnitudes and the secondary safing vector pair on the spacecraft.

All instrument teams delivered science data for archive #10 on or prior to Oct. 1 as scheduled. This data spans the time from Oct. 1 through Dec. 31 of 2006.

Tuesday, Oct. 30 (DOY 303)

Last Friday the Science Planning portion of the SOPU process for S37 was completed. Today development was officially handed off to Uplink Operations to finalize the products that will be sent to the spacecraft.

A Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference was held today. The topic: Probing the Mysteries of Iapetus. Presentations were given by representatives from VIMS, ISS, UVIS, RADAR, and CIRS.