Cassini Significant Events 12/21/06 - 01/03/07

January 5, 2007

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired on Wednesday, Jan. 3, 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

Due to the holidays, the report published this week will cover the two-week period from Dec. 21 through Jan. 4, 2007.

Thursday, Dec. 21 (DOY 355):

The Titan Atmospheric Model Working Group (TAMWG) met on Dec. 20 to discuss the Titan 21 flyby atmosphere density estimates. Ion and Neutral Mass Spectrometer (INMS), AACS, and Navigation personnel reported their Titan density results. The AACS results were reported as 11.1x10-10 kg/m3 at 1000 km closest approach. The INMS results were presented as 1.92x10-10kg/m3 but were considered preliminary since earlier calculations showed a larger value. The final INMS results will be available later this year. UVIS presented some past results that showed consistency with previous INMS results. Navigation presented results that showed consistency with AACS results. Differences between AACS and INMS values are still not understood. The next TAMWG meeting will be devoted to examining past results and coming up with a new density model for future flybys.

Three of the "Top 100 Science Stories of 2006" come from Cassini, according to the January 2007 issue of "Discover" magazine. Titan's methane rain, Enceladus' geysers and the solar occultation photo of Saturn are all highlighted. The latter image appears on the cover of "Discover," just as it had on "National Geographic" last month. Interestingly, among the top one hundred, astronomical topics are covered in thirteen, including seven solar system stories and two others about extra-solar planets.

The Encounter Strategy Meeting for Titan 22-Titan 23 was held today. It covered the period from Dec. 28 to Jan. 13, and Orbit Trim Maneuvers (OTM) 86 through 88.

Friday, Dec. 22 (DOY 356):

On Dec. 22, tracking data from the spacecraft converged sufficiently to allow the OTM-85 maneuver decision to be based on that day's orbit solution. OTM-85 would have a delta V of 23.4 mm/s. The cost of cancellation on the down stream maneuvers was estimated to be about 0.6 m/s. OTM-85 execution or cancellation does not significantly affect the execution of OTM-86. Given the not unreasonable delta-V cost of cancellation and the timing of the maneuver - planned for Christmas morning - the Program Manager decided to cancel the maneuver. There was much rejoicing as program personnel dashed for their cars to begin the holiday weekend.

A Live Update Kickoff meeting was held today. It was thought that Go/No-Go analysis would take place over the holidays due to the timing of the release of the Navigation orbit determination solution for OTM-85 and the uplink windows for this product. Instead, with the cancellation of OTM-085, the pointing errors in the "watch" region improved considerably by around 0.3 mrad. Science Planning recommended a "no go" for the update as all observations fully met pointing requirements. The update has been cancelled.

Sunday, Dec. 24 (DOY 358):

Two years ago the Cassini flight team celebrated the holiday season with the successful release of the Huygens Probe on Dec. 24, 2004.

Monday, Dec. 25 (DOY 359):

JPL Holiday.

Tuesday, Dec. 26 (DOY 360):

Cassini outreach joined the Sidewalk Astronomers for the annual winter public Star Party at Death Valley's Furnace Creek Visitor Center. About 300 park visitors listened to a talk followed by star gazing through mostly cloudy skies with temperatures hovering near freezing. Additional stargazing was offered on Dec. 27-30.

On DOY 360, a couple days before Titan closest approach, the Composite Infrared Spectrometer (CIRS) carried out a composition mapping of Titan to obtain measurements of nitriles, hydrocarbons, and carbon dioxide as a function of latitude and emission angle at Titan's equator. Titan's gas composition exhibits significant variation with latitude and season. Long integrations will permit a sensitive search for new molecules.

Wednesday, Dec. 27 (DOY 361):

Cassini made the list as one of the top exploration and discovery stories of the year for NASA. It was reported that the Cassini spacecraft may have found evidence of liquid water reservoirs that erupt in Yellowstone-like geysers on Saturn's moon Enceladus. The unusual occurrence of liquid water so near the surface of Enceladus raises many new questions about the mysterious moon. Cassini also discovered two new rings around Saturn, confirmed the presence of two others, and photographed something never before seen on another planet - a hurricane-like storm at Saturn's south pole.

The feature "Cassini Rings in the New Year" made its debut on Dec. 27, and was promoted in several high visibility locations. The Flash version is available at:
The html version is available at:

The Cassini Photo Contest II is currently running on the outreach website. It was originally planed to announce the most popular photo in early February, but due to popular demand, the announcement date may occur sooner. Keep an eye on the starting page for any news. For more information or to participate link to:

Thursday, Dec. 28 (DOY 362):

As a late Christmas present, on Dec. 28 Cassini flew by Titan at an altitude of 1300 km, and a speed of 6 km/sec. This was the lowest altitude reaction wheel controlled encounter to date. AACS performed nominally, with the RWA spin rate changes due to the imparted atmospheric torque well within the acceptable rpm bounds.

The Radio Science Subsystem (RSS) tracked the spacecraft from Earth before, during, and after Titan closest approach. RSS obtained Doppler and ranging data to deduce details of Titan's gravity field, and hopes to determine the possible existence of an internal ocean by measuring the dynamic Love number, K2, of Titan.

T22 was a far-infrared focused flyby for the Composite Infrared Spectrometer (CIRS), featuring two surface temperature maps and two composition integrations. The former aims to detect surface temperature variations in a window region near 20 microns, while the latter is designed to map the spatial variation of Carbon Monoxide (CO), Hydrogen Cyanide (HCN), and water (H2O) via far-infrared rotational lines.

The entire suite of Magnetospheric and Plasma Science (MAPS) instruments, which include the Cassini Plasma Spectrometer (CAPS), Cosmic Dust Analyzer (CDA), Ion and Neutral Mass Spectrometer (INMS), Magnetometer Subsystem (MAG), Magnetospheric Imaging Instrument (MIMI) and Radio and Plasma Wave Science (RPWS), simultaneously performed observations to study the interaction of the magnetosphere with Titan at intermediate distances for evidence of ion pickup, radio emissions, density profiles, and the general wave environment.

Around closest approach, INMS sampled Titan's atmosphere/ionosphere to determine its composition and thermal structure.

Immediately after the flyby, RPWS measured the properties of equatorial plasma waves and dust.

Friday, Dec. 29 (DOY 363):

In celebration of the holiday season and the close of another remarkable year at Saturn, the Imaging Team for NASA's Cassini mission presented a smorgasbord of Saturnian imagery showing heavenly bodies great and small, in motion, and in three dimensions.

The image products released include color views, movies, maps and
3D anaglyphs. They are available at: .

Saturday, Dec. 30 (DOY 364):

Uplink Operations began sending up the first instrument expanded block files to the spacecraft in support of S27. Orbit Trim Maneuver #86 is scheduled for tomorrow so the remaining files will be sent on Jan. 1 and 2.

Today is the sixth anniversary of the Cassini flyby of Jupiter on Dec. 30, 2000.

The Media Relations Office produced the latest Cassini video log highlighting some of the most recent discoveries, to view just visit:

Sunday, Dec. 31 (DOY 365):

OTM # 86 was performed today. This was the cleanup maneuver from the Titan 22 encounter on Dec. 28. The main engine burn began at 4:15AM PDT. Telemetry immediately after the maneuver showed a burn duration of 2.95 seconds, giving a delta-V of 0.46 m/sec as planned. All subsystems reported nominal performance after the maneuver.

Monday, Jan. 1 (DOY 001):

JPL Holiday.

Tuesday, Jan. 2 (DOY 002):

The last instrument expanded block files for S27 were uplinked on Jan. 1 and today over DSS-65 along with the S27 background sequence. The sequence will begin execution on Jan. 5.

Jan. 1, 2007, was the scheduled date for the seventh delivery of Cassini science data to the Planetary Data System. This delivery covers data collected from January to March 2006. Of the 12 instrument teams, 8 are 100% complete. Some calibration files remain to be delivered, and plans are in place to deliver the remaining data shortly.

Wednesday, Jan. 3 (DOY 003):

Radar scientists report definitive evidence of the presence of lakes filled with liquid methane on Saturn's moon Titan in this week's journal Nature cover story. The JPL Media Relations Office supported this special issue with a web feature, Photo journal release, and Podcast. For more details visit: