From: Jet Propulsion Laboratory
Posted: Saturday, August 22, 2009
The most recent spacecraft telemetry was acquired on Aug. 18 from the Deep Space Network tracking complex at Goldstone, California. 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: http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Friday, Aug. 14 (DOY 226):
During the maneuver design process for Orbit Trim Maneuver (OTM) #213, the Navigation team realized that there were some benefits to be gained if the team were to deviate from the planned trajectory for this OTM. OTM-213 is a relatively large maneuver, and by moving the Titan aim point 15 kilometers from the reference target, the project would save approximately 2 m/s in delta-V, and would actually be put closer to the original reference trajectory further down stream. A small wrinkle in this plan was that the RADAR observations at Titan 61 might need an unplanned live update. The change in aimpoint for OTM-213 was approved and the sequence leads will go ahead with the live update.
Sunday, Aug. 16 (DOY 228):
Orbit Trim Maneuver (OTM) #213 was performed today. This is the apoapsis maneuver setting up for the Titan 61 encounter on Aug. 24. The main engine burn began at 8:29 AM PDT. Telemetry immediately after the maneuver showed the burn duration was 76.5 seconds, giving a delta-V of 12.99 m/s. All subsystems reported nominal performance after the maneuver.
The temperature transducer on the main engine A combustion chamber that previously read erroneously during OTM-183 read erroneously again during OTM 213. It has read 255 DN since the start of the burn. 255 DN typically indicates an open circuit, suggesting it may have permanently failed. The other transducer on the engine A combustion chamber continues to read nominal and is used by the Autonomous Thermal Control (ATC) 7 algorithm. It is clear the propulsion hardware is performing normally from a thermal perspective and this problem is isolated to the failed transducer. This transducer was marked as dead in System Fault Protection after OTM-183 and cannot cause adverse fault protection responses.
Monday, Aug. 17 (DOY 229):
After reviewing the trajectory files delivered on Friday, it was decided that a simpler Titan sequence update was all that was needed instead of a RADAR Inertial Vector Definition re-delivery. The RADAR instrument team has stated that the current Synthetic Aperture Radar observation looks fine. The plan is to deliver products Tuesday, hold a command approval meeting Thursday, and uplink on Friday.
Tuesday, Aug. 18 (DOY 230):
Today is the 10th anniversary of the Cassini Earth flyby on Aug. 18, 1999.
The Target Working Team (TWT)/ Orbiter Science Team (OST) integrated products for S58, covering orbits 127 through 129, from March 2010 through April 2010, were delivered today. The integrated products are in their final form and no re-integration is planned. The next step in sequence development, Science Operations Plan (SOP) implementation, will kick off on Aug. 20. Between now and then, the instrument teams will be working on pointing designs for the sequence. TWT/OST teams deliver integrated sequence products for the extended mission about every five weeks.
The sequence leads for S53 began uplinking instrument expanded block files to the spacecraft today in preparation for the start of execution on Aug. 19. Eight files were sent. The CDS version 10 flight software patch, scheduled for uplink in September, has been delayed to allow more time for validation and review, as well as to help with conflicts in DSN tracking time caused by the proximity of the planned uplink and the downlink of the high priority science data collected around the time of the equinox crossing.
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