Cassini Significant Event Report

For Week Ending 12/17/04

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, December 15. The Cassini spacecraft is in an excellent state of health and is operating normally. As of yesterday (December 16), the Program is 8 days from Probe release and 29 days from Probe relay. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" web page located at .

The S06 background sequence completed on the spacecraft this week. A number of key activities had to be performed on the ground in support of the Titan-b (Tb) and Dione flybys. Within three days, the Dione live update process kicked off, a Go/No Go meeting was held, and the necessary Dione and Mimas vector files were uplinked to the spacecraft along with Radar trigger commands. All executed as expected on December 14. After Dione, files were sent to the spacecraft to open the Main Engine cover in preparation for Orbital Trim Maneuver 8 (OTM), the Probe Targeting Maneuver (PTM). The PTM executes on December 16.

This week's main event was the Titan-B flyby with closest approach on 348T11:38 Spacecraft Event Time. At this time the orientation for CAPS allowed it to observe Titan's ionosphere and magnetospheric interaction on the inbound leg and until 25 minutes after closest approach. The Composite Infrared Spectrometer (CIRS) performed a 2-hour limb integration using the mid-IR detectors to search for new molecules in Titan's stratosphere. CIRS continued the campaign of far-IR integrations begun at T0 to search for species at longer wavelengths, and obtain a thermal map of the stratosphere, lending insight into the dynamics of Titan's atmosphere.

After a two-day Titan movie sequence where the Imaging Science Subsystem (ISS) looked for cloud motions, Tb provided opportunities for imaging at high-resolution with pixel scales as small as a few 10s of meters and phase angles as low as 16 degrees. ISS observations included the locations of the specular points during both Ta and Tb, and of the Huygens landing site that will provide stereo coverage once the data from T10 is obtained. Outbound ride-along observations with VIMS provided a view of Titan's north polar region illuminated by Saturn-shine.

From the Magnetometer Subsystem (MAG) point of view, the objective of Tb was to study the development of the near wake or magnetotail after Ta had provided observations of the roots of it. MAG science will thus be an important part of the three flybys Ta, Tb, and T3, which all occur at almost the same Saturnian local time. These flybys are also important because of the increased variability of the incident plasma flow in the Saturnian magnetosphere close to Saturnian local noon.

The Visual and Infrared Mapping Spectrometer (VIMS) actively observed the surface of Titan at small solar phase angles, investigated the formation and evolution of clouds on Titan, and searched for lightning, hot spots, and characterization of airglow.

The Ultraviolet Imaging Spectrograph (UVIS) executed a series of EUV/FUV scans across Titan to create spectral images, and performed two important stellar occultation measurements to better understand Titan's upper atmosphere, which will be used to support spacecraft operations later next year, as well as for science purposes.

Following the Titan-B flyby, CIRS obtained its first dark side FP1 map of Dione on Rev B. CIRS looked for thermal anomalies and will use the data to investigate Dione's thermal inertia. This flyby was the third closest approach to Dione - at approximately 80,000 kilometers - during the nominal tour. ISS observations were taken of the trailing hemisphere of this satellite where the strange "wispy streaks" are located.

The Spacecraft, Uplink, and Navigation teams completed the last official Operational Readiness Test (ORT) on December 9. This test ran from Probe Release through the playback of the Probe Imaging Optical Navigation images. The timing was very tight with multiple interfaces and the ORT was useful in flushing out issues.

Conforming Planet Physical and Cartographic Constraints files were released by Instrument Operations. One contains Sun, Earth, Moon, Jupiter, Saturn and Uranus and major Saturnian satellites and is compatible with the new reference trajectory. The other contains minor Saturnian satellites and outer irregular satellites and is compatible with the new Rocks Spacecraft and Planet ephemeris data file.

In preparation for the start of execution on December 16, thirteen instrument files were uplinked to the spacecraft along with the S07 background sequence.

Preliminary Sequence Integration and Validation 2 Cycle 1 products were delivered as part of the Science and Sequence Update Process for S08. S09 is still in the Sub-Sequence Generation phase of development. Teams are currently validating pointing designs with respect to the new reference trajectory.

The results of the ACS analysis of the port #1 delivery for S10, S39, and S40 have been published. S10 is currently in Science Operations Plan (SOP) Update and S39/S40 are in SOP Implementation.

The decision meeting for the Aftermarket process for S12 was canceled this week since all of the requested changes fit within the allocated resources.

The VIMS team has begun investigation of the feasibility of rerunning early cruise VIMS data with newer telemetry processor. This would improve the quality of the data going to archive next year. Evaluation of known problems and a test run of data is underway.

All teams and offices supported this month's Cassini Monthly Management Review.

Two delivery coordination meetings were held this week. The first was a Mission Planning delivery of AP_DOWNLINK V6.0, and the second was for an updated version of the Command Data Base 11a. This delivery will be used with Mission Sequence Subsystem version D11 when it is delivered in May of next year.

The Mission Support and Services Office reported that they have had to rescind an offer of ACE support to the Deep Impact project. Now that the Deep Impact launch has moved to January 12, it is very close to Probe Relay operations. Neither project wanted to negatively affect operations for the other, so the support was cancelled.

European Space Agency (ESA) scientists have teamed up with the Joint Institute for Very Long Baseline Interferometry in Europe (JIVE) for an experiment, which is expected to bring unique information from the Huygens probe during its descent through Titan's atmosphere. They intend to use a technique called Very Long Baseline Interferometry (VLBI) to pick-up the probe's faint radio signal here on Earth and use it for reconstruction of the descent trajectory of the probe in the atmosphere of Titan. For more information, go to the ESA web site at

The most recent Cassini Mission Status Report can be found at

Image advisories, press releases and the latest Cassini information can be found at