5 min read

Significant Event Report for Week Ending 11/19/2004

Cassini Significant Event Report

For Week Ending 11/19/04

The most recent spacecraft telemetry was acquired from the Madrid tracking station on Wednesday, November 17. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" web page located at http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Science activities this week began with images taken of newly discovered moons by the Imaging Science Subsystem (ISS). The Ultraviolet Imaging Spectrograph (UVIS) continued obtaining mosaics to determine the density of neutrals in the inner magnetosphere. While inside the magnetosphere, the suite of Magnetospheric and Plasma Science (MAPS) instruments continued its magnetospheric boundaries investigation in the dawn sector at southern latitudes and at a variety of radial distances. Once outside of the magnetosphere, the instruments monitored the solar wind.

The Titan Atmosphere Model Working Group met in Pasadena, CA this week to discuss instrument measurements and ACS results from the Titan-a flyby. Although the flyby occurred less than a month ago, all applicable data was processed in time for the meeting as promised. Key results were:

* No significant argon in Titan's atmosphere.

* Methane abundance is 1.8% +0.5%.

* CIRS and INMS density values are consistent with post-T0 models.

S05 activities concluded this week with the radiation of Reaction Wheel Assembly (RWA) bias commands that will execute in S06, along with the radiation of the S06 Instrument Expanded Blocks and background sequence.

S06 began execution on Monday November 15, and runs for 31 days until December 16. During this sequence the flight team will support two Orbit Trim Maneuvers - #6 and #7 -, the Titan-b flyby on December 13, a Dione flyby on December 15, and uplink a live Inertial Vector Propagator (IVP) update. During S06, the DSN will support the program with 38 station passes, 16 of which will be over 70 meter antennas.

A Huygens Playback Meeting was held to review the ground system processes for support of Probe Checkout F16. The focus was on processed telemetry receipt and data transfer to the Huygens Probe Operations Center in Darmstadt, Germany. A follow-up meeting will be held next week.

Initial activities in S06 included an RWA bias, uplink of the Probe Checkout mini-sequence, and uplink of some testing files for the Cassini Plasma Spectrometer.

Although execution of S06 has begun, some items are still in development. The sequence development leads have laid out and distributed a schedule for the Titan-b live IVP update. The Titan Orbiter Science Team /Science Team responsibility for a live update is to take the new trajectory delivered by the Navigation team and determine if the live update is still required to meet designs and present this at a "GO/NO-GO" meeting. For the Phoebe live update a single driving instrument did this work, but it was determined that science participation by any instrument that cares about the details of PRIME pointing was more useful. The process will kick off on November 19, a go/no go meeting will be held on November 22, and if approved, a command approval meeting will be held on November 30.

Sequence development is ongoing for tour sequences S06 through S12, and S37 through S41.

Science Operations Plan (SOP) implementation of S41 - the final sequence in Cassini's prime mission - began this week.

Requested changes to S12 were due this week prior to next week's assessment meeting and kick off of the Aftermarket process.

Teams made the official port 2 delivery for the S09 SOP Update process.

Sequences S07 and S08 continue in the Science and Sequence Update Process (SSUP). This is the final process prior to sequence execution. A Preliminary Sequence Integration and Validation (PSIV) Sequence Change Request approval meeting was held for S07. Ten changes were approved and one withdrawn. In addition, stripped files were distributed back to participating teams for the PSIV2 portion of the process. For S08, the merged background sequence and SEG products were released as part of PSIV1.

A delivery coordination meeting was held for new a version of the Radio Science Subsystem (RSS) programs PREDICTS, LMBTRK, and BISTAT. New versions of the software were delivered to the Program Software Library for archive and will become operational to support RSS operations.

The PREDICTS software computes the expected received frequencies as a function of time. It generates a Downlink Frequency File (DLF), which is an input file to the Radio Science Receivers at the DSN stations.

The LMBTRK software computes the direction at which a radio signal must be sent in order to reach the ground station after traversing an atmosphere. It generates an Inertial Vector Definition (IVD) file, which is an input to the Pointing Design Tool.

The BISTAT software computes the direction at which a radio signal must be sent in order to reach the ground station after bouncing off a planetary body. It also generates an IVD file.

Cassini outreach attended a special showing of the Cassini "Ring World" planetarium show in the Rauch Planetarium, Gheens Science Center, University of Louisville, and attended a second show plus public star party for the local cub scouts. Ring World is available as part of the school group show library at the planetarium.