Cassini Significant Events 10/17/07 - 10/23/07

October 25, 2007

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired on Tuesday, Oct. 23, from the Madrid 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. 17 (DOY 290):

Throughout this week, Uplink Operations will be sending commands to the spacecraft to perform a DOY-291 real-time reaction wheel bias, a memory read out (MRO) and scrub of the sub-module flags, and an MRO of the CDS for Composite Infrared Spectrometer (CIRS) bus interface unit data. In addition the S34 Hyperion mini-sequence, S34B background sequence, Radio Science (RSS) Saturn Occultation Live Movable Block for DOY-297, and a RADAR trigger command will be uplinked.

Thursday, Oct. 18 (DOY 291):

The Hyperion mini-sequence began execution today. Science instruments performed observations to determine the color and rotation of the satellite. Later this week, the cameras will take measurements in support of a satellite orbit determination campaign.

Friday, Oct. 19 (DOY 292):

A non-targeted flyby of Hyperion occurred today.

The Cosmic Dust Analyzer (CDA) instrument team began a 14-hour long decontamination of the instrument's detector today. Decontaminations occur at regular intervals and are part of normal CDA instrument maintenance.

Monday, Oct. 22 (DOY 295)

A non-targeted flyby of Titan occurred today. For this event, the Imaging Science Subsystem (ISS) took full disk stereo images and worked to fill gaps in previous data sets, while the Visual and Infrared Mapping Spectrometer (VIMS) performed global mapping. CIRS obtained measurements of nitriles, hydrocarbons, and CO2 as a function of latitude and emission angle at the equator on Titan. Titan's gas composition exhibits significant variation with latitude and season. Long integrations will permit a sensitive search for new molecules. CIRS also continued to develop temperature maps of Titan to obtain information on the thermal structure of Titan's stratosphere.

S34B, the fourth and final part of the S34 background / CDS flight software uplink and checkout / Hyperion mini-sequence began execution today.

Tuesday, Oct. 23 (DOY 296)

Non-targeted flybys of several of the smaller satellites occurred today.

Non-targeted flybys are ones that occur without active navigation and "just happen" to be in a place that can be observed by the instruments on board Cassini. Typically the altitudes are high, anywhere from several thousand to a million km, and may vary as the reference trajectory changes.

Additional science opportunities this week as a result of the numerous non-targeted flybys included spectrophotometry and phase coverage of Tethys, Enceladus, and Mimas, Enceladus and Mimas global color mapping, and CDA observations at the outer ring, Rhea, Dione, and at the Enceladus orbit crossing.

The Cassini Radio Science Orbit 51 atmospheric occultation was completed today. The experiment included ingress and egress atmospheric occultation observations of the ionosphere and neutral atmosphere of Saturn, and was the only Cassini Saturn occultation to probe nearly equal mid-Southern latitudes on both the ingress and egress sides, providing unique characterization of the atmosphere at similar latitudes but at widely separated longitudes. The atmospheric occultation went very well. The experiment was completed as planned and high quality data were collected at all three observation frequencies of S, X, and Ka bands.

CIRS complemented the RSS occultation observations with Saturn occultation point mosaics. These CIRS spectra in the vicinity of RSS occultation points are used in combination with the RSS measurements to obtain a new determination of helium abundance. In the absence of a probe into Saturn, we rely on remote sensing techniques for the determination of the helium abundance, and refinement of such determinations is a high scientific priority. By repeating the observations at a number of occultation points under a variety of atmospheric conditions, an improved value with reduced error bars can be obtained.

The newest Cassini "Scientist for a Day" program was announced Oct. 23. Students in grades 5-12 are invited to choose from four possible targets for the cameras on board Cassini on Nov. 30, 2007. The program asks students to decide which target's image would provide the greatest scientific value. Submission deadline is November 15. For more information about the Cassini Scientist-for-a-Day contest and entry rules, please visit:

Additional information can be found at:

A beautiful full ring image was selected as Astronomy Picture of the Day today.