Cassini Significant Events for 04/20/06 - 04/25/06 The most recent spacecraft telemetry was acquired Tuesday, April 25, 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 . Cassini Significant Events 04/20/06 - 04/25/06 Thursday, April 20 (DOY 110) Radio Science performed periodic instrument maintenance today along with an Ultra Stable Oscillator characterization. The Software Requirements and Certification Review for the CDS Command Loss Timer (CLT) flight software patch occurred today. Since a formal meeting was not required, the documentation was submitted directly to the System Engineering Office. This patch is planned for uplink on May 8-11. It corrects a code error found last September. Friday, April 21 (DOY 111) The Mission Support & Services Office has provided some approximate numbers of the amount of science data that has been collected since January 1, 2004. The data is complete through April 19, 2006. Instrument Data: CAPS 26,283,460kbytes CDA 8,770,209kbytes CIRS 7,135,426kbytes INMS 801,804kbytes ISS 24,057,854kbytes MAG 10,465,190kbytes MIMI 8,360,273kbytes RADAR 1,650,522kbytes RPWS 39,422,594kbytes UVIS 6,021,474kbytes VIMS 5,605,781kbytes Total science data is 138,574,587kbytes or roughly 132 gbytes. The final real-time command executed during S19 was an end of sequence reaction wheel assembly bias. As S19 drew to a close, the Composite Infrared Spectrometer (CIRS) continued with 60N latitude Saturn composition measurements and their first northern hemisphere temperature map of Saturn at 10N latitude, the Cosmic Dust Analyzer (CDA) continued with a search for Saturnian dust stream particles, and the Ion and Neutral Mass Spectrometer (INMS) with scans for dense particle regions far from Saturn. Saturday, April 22, (DOY 112): S20 began execution on Friday, April 21, at 11:30PM Pacific Time. The sequence will run for a little over 41 days and will conclude on June 2. During this time, five orbit trim maneuvers (OTM) are scheduled, numbers 58 through 62. Status at this time is that OTMs 58 and 59 will execute as planned, and OTM-060 has been deleted. There will be two targeted flybys of Titan during S20 numbered Titan 13 and Titan 14. The one live update of the sequence beginning on DOY 115 was cancelled when existing pointing met science requirements. This is the first time a sequence has been flown that has been split using software developed for that purpose. At the top of S20, science observations included three Imaging Science Subsystem (ISS) observations of mutual events capturing a transit of Enceladus across Janus, a transit of Enceladus across Epimetheus, and a transit of Janus across Epimetheus. In addition, the Ultraviolet Imaging Spectrograph (UVIS) performed a stellar calibration with the star Alpha Virginis, and then observed Hyperion in order to measure its UV albedo across longitude and phase space, and CIRS completed a mid-infrared mapping of Saturn to determine upper troposphere and tropopause temperature. Observing temperature gradients and thermal eddies above troposhperic jets and waves will give information about the dynamical activity and its propagation or decay into the stratosphere. Monday, April 24 (DOY 114): At the weekly Project Science Meeting one of the topics of discussion was a request from the Titan Orbiter Science Team (TOST) to the Cassini project to think about a data recovery strategy for Titan 13. The unique data being captured at T13 includes a UVIS solar occultation and a full synthetic aperture RADAR swath. At this time, the most desirable option appears to be that if a DSN outage occurs during the middle of the downlink, and the project recovers command capability before the end of the pass, then science would like to propose uplinking commands to zero-out the Data Policing Table to prevent TOST Data from being overwritten by cross discipline data during the following Observation Period and the following downlink. The PRIME observations that would be zeroed out are a series of Icy Satellite Observations, all at about 1 to 2 million km distance, and all high phase. The Magnetospheric and Plasma Science (MAPS) and rider instruments would also be affected. There will be a technical coordination meeting tomorrow with the S20 sequence leads, Spacecraft Operations, Mission Planning, and Science Planning to discuss implementation of this request. FOLLOWUP: After the Project Science Meeting, the rings group appealed to the Project Scientist to reevaluate the decision of what data should be preserved in the event of a DSN outage during playback. The fact that rings observations would also be played back during the time of concern had been unintentionally overlooked at the meeting. The final decision will be made Wednesday. Tuesday, April 25 (DOY 115): The remaining files for the April 1 Archive delivery have been received. All teams have now delivered 100% of the data. 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 Space 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.
