Cassini Significant Events for 08/31/06 - 09/06/06 The most recent spacecraft telemetry was acquired Wednesday, September 6, from the Goldstone tracking stations. 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 . Thursday, August 31 (DOY 243): The Titan 17 flyby, scheduled for September 7, is set for an altitude of 1,000 km. This flyby is at the relatively low latitude of 23 degrees, in the region where the Titan atmosphere model predicts a greater atmospheric density. If the results from this flyby indicate that is true, as measured by the ACS thruster duty cycle and INMS instrument data, trajectory changes will be considered for Titan 20, which is at 1030 km altitude, but almost equatorial at 7.5 degrees. A new candidate reference trajectory has been developed with an increase in the altitude of the Titan 20 flyby from 1030 to 1055 km. The final decision to raise the T20 altitude, or not, will occur at the Titan Atmosphere Model Working Group meeting on September 11. If the decision is to raise the altitude, the new trajectory will go into effect on September 12. Spacecraft Operations Office personnel held an Exciter RF Loss tabletop exercise today. This is the first in a periodic sequence of such exercises for SCO training. The Radio Science Subsystem (RSS) performed the first of three Operational Readiness Tests (ORT) today using the Deep Space Network antennas at Goldstone. Tests two and three will be performed Saturday and Sunday. These ORTs are used to prepare for the RSS Saturn gravity observation on September 9. Friday, September 1 (DOY 244): The S23 sequence leads made the decision to give up the last hour of the Cassini DSN track over Goldstone today to accommodate station maintenance work. A glitch with the transmitter was preventing successful uplink of command files. Maintenance will go toward ensuring the station is available for the maneuver uplink on Monday. According to Science Planning, only real-time data was lost. The recorded data will be played back from the SSRs with no loss. Monday, September 4 (DOY 247): Orbit Trim Maneuver (OTM) #70 was performed today. This is the minus 3-day maneuver setting up for the Titan 17 encounter on September 7. The reaction control subsystem burn began at 12:45 PM. Telemetry immediately after the maneuver showed the burn duration was 164.1 seconds, giving a delta-V of approximately 227.6 mm/s. All subsystems reported nominal performance after the maneuver. The Imaging Science Subsystem (ISS) began a 12.5 hour observation of Saturn's Ring System today. Images of the unlit face of the Cassini Division at high phase were taken once every 8 minutes. This observation will be used to search for dust, clumps and variations in the structure of the outer B Ring. Tuesday, September 5 (DOY 248): The kickoff meeting was held today for the S23 Enceladus/Tethys Live Inertial Vector Propagator (IVP) update for DOY 252-253. The final orbit determination solution became available last Thursday, and analysis is scheduled to begin later today. Navigation has recommended that teams look at the size of the uncertainties as part of the decision process to perform or not perform the update. A beautiful image of the white cliffs of Dione was Astronomy Picture of the Day today. Wednesday, September 6 (DOY 249): The Spacecraft Operations Office has requested the S25 sequence lead to schedule a test of the Titan 20 flyby in the Integrated Test Laboratory. The Project Briefing, the final meeting held as part of the Science Operations Plan Update process, was held today for S26. Input products for the sequence will be handed off to the sequence leads at the end of this week, and the final development process will kick-off on September 12. Today concluded with the spacecraft on approach to Titan for the T17 encounter, an inbound flyby. The Composite Infrared Spectrometer (CIRS) began a 7+ hour activity to obtain information on the thermal structure of Titan's stratosphere, with ISS and the Visual and Infrared Mapping Spectrometer (VIMS) taking advantage of the spacecraft pointing to gather data on Titan. Wrap up: Check out the Cassini web site at http://saturn.jpl.nasa.gov for the latest press releases and images. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Spsce Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.
