Significant Event Report for Week Ending 12/20/2004

December 22, 2004

(Source: Jet Propulsion Laboratory)

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Monday, December 20. The Cassini spacecraft is in an excellent state of health and is operating normally.  As of today (December 21), the Program is three days from Probe release and 25 days from Probe relay.

The S07 background sequence began execution on Thursday December 16. This sequence will run for 37 days and will end on January 22, 2005.  During this time, five Orbital Trim Maneuvers (OTM) will execute - one of which is the Probe Targeting Maneuver.  There will be one targeted flyby of Titan, one non-targeted flyby of Iapetus, the Huygens Probe will be released from the Cassini Spacecraft, and Probe Relay will occur.

Science this week consisted of Saturn Magnetospheric studies performed by the Cassini Plasma Spectrometer, Ion and Neutral Mass Spectrometer, Magnetometer Subsystem, Magnetospheric Imaging Instrument and Radio and Plasma Wave Science instrument.

On board activities this week primarily involved preparations for the Huygens Probe separation event.   Orbital trim maneuver #8 was successfully completed on the spacecraft on December 16.  This maneuver, also called the Probe Targeting Maneuver, places Cassini on a Titan entry trajectory in preparation for the Huygens probe mission.  The main engine burn began at 6:30 p.m. Pacific Time.  The "quick look" immediately after the maneuver showed the burn duration was 84.9 sec, with a delta-V of 11.9 m/s, as planned.  ACS, Propulsion, and Thermal teams all reported a nominal burn.

Also on December 16, the Huygens primary mission commitment meeting was held. The participants were NASA, the European Space Agency, and JPL management as well as Cassini and Huygens project management. The participants reviewed the final report from the Mission Risk Review and status and readiness assessments from both Cassini and Huygens. All reports were favorable and the decision was made to proceed with the primary Probe mission.

On December 19 and 20, the Probe Relay critical sequence was loaded to the SSRs, the baseline High Gain Antenna pointing vectors were uplinked for the Probe Relay sequence, and the Mission Timer Unit that will activate the Probe shortly before atmospheric entry was loaded and its countdown begun.

The Iapetus late update kick-off meeting was held this week.  The files will be uplinked to the spacecraft on December 30 for execution on the 31st. An Iapetus science preview meeting was held on December 20 to present the science goals and plans for the upcoming close non-targeted flyby on January 1.

Official port#1 occurred this week as part of Science Operations Plan (SOP) Implementation of the S41 sequence.  The team products are in the process of being merged and will be delivered to ACS for the end-to-end pointing validation after the New Year.

All sequence development including the Aftermarket, SOP Update, Science and Sequence Update Process and SOP implementation processes stand down for the period of December 18 through January 2.  This decision was made to allow teams to focus on Probe Release operations and to squeeze in time with their families.

The revised Mission Sequence Subsystem (MSS) D11 baseline plan, based on the final set of Engineering Change Requests (ECR), was presented at the Ground Software Monthly Management Review.  There is one more likely ECR to be submitted for D11 addressing a data loss issue that arose in S06.

An image of Prometheus stealing particles from Saturn's F ring and one of an illustration of the Probe landing on Titan were Astronomy Pictures of the Day on December 17 and 20.

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