Cassini Significant Events for 04/13/06 - 04/19/06 The most recent spacecraft telemetry was acquired Wednesday, April 19, 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, April 13 (DOY 103) A successful end-to-end test was held in the Integrated Test Laboratory (ITL) for a CDS Command Loss Timer (CLT) patch to be uplinked to the spacecraft beginning May 8. The patch corrects a code error discovered last September when the CLT was set to a different value for OTM-31, which caused a data loss for the Titan-7 flyby. A temporary patch to restore normal operations was uplinked at that time. This patch is a permanent fix to the code. The uplink readiness review for this delivery will be held on April 17, followed by a Software Requirements and Certification Review on April 20. As was reported last week, the final step in the Monopropellant Tank Assembly (MTA) recharge and flight software patch procedure was to be a reaction wheel assembly (RWA) bias. This bias, the first use of thrusters after the MTA recharge, executed successfully and provided an opportunity to perform an in-flight calibration of the higher thrust levels. There were no red alarms, no rejected commands, and no unexpected fault protection (FP) activity. The attitude error was small and well below the FP threshold. Friday, April 14 (DOY 104) After input was received from Science Planning and participating science teams, it was determined that the DOY 115 Live Inertial Vector Propagator update could be cancelled. Analysis showed that the highest error is 0.38 mrad for Janus, with most of the errors below 0.1 mrad. A team from JPL Media Relations filmed two classrooms in the Bay Area. These two classrooms were working through the "Reading, Writing, and Rings" lessons. The footage collected from this filming will be edited with interviews of the content developers. The final products will serve two purposes: to expose audiences to the curriculum as well as to train educators in the pedagogy of the lessons. The outreach team submitted the following information on Saturn viewing. Whether you live in the city or the country, you can view Saturn and Mars this month. Just look to the west in the evening, about halfway between horizon and overhead. Both planets can be spotted near the Gemini Constellation in the western sky. Here's where to look: http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=1089 Monday, April 17 (DOY 107): Final sequence approval and command approval meetings were held for the S20 background sequence and related files. During the evening pass over Goldstone, all seven instrument expanded block files were uplinked to the spacecraft. Part one of the background sequence will go up to the spacecraft on Wednesday. An ITL run for Orbit Trim Maneuver (OTM) #58, originally planned for April 17 and 18, was cancelled. The test was to verify the first-time event of powering on the accelerometer over an RCS burn in order to calibrate the thrusters following the MTA recharge performed last week. It turns out OTM-58 will be too small. ACS wants an RCS burn with a delta-V of at least 0.1 m/sec. The Spacecraft Operations Office will try again with OTM-59, which is currently estimated at about 0.3 m/sec. The S22 Science Operations Plan Update official input port occurred today. The merged products are currently being run through the end-to-end pointing validation process by ACS. The Project Briefing and Waiver Disposition Meeting is scheduled for Wednesday, April 26. The SOP Update product is handed off to uplink operations on Friday, April 28. Tuesday, April 18 (DOY 108): For S21, the leads are planning to schedule an ITL test to ensure that de-registration of S20 part 2, and the registration of the S21 background sequence occur as expected. S21 will be the first time a sequence is uplinked following a split sequence. The simulation coordination meeting will occur on April 21. Science activities this week included the continuation of the Cosmic Dust Analyzer search for Saturnian dust stream particles, Composite Infrared Spectrometer high spectral resolution composition observations of Saturn - this time they will be observing at 60N latitude - and Ion and Neutral Mass Spectrometer scans for dense particle regions far from Saturn. The Imaging Science Subsystem has wrapped up its icy satellite high phase spectrophotometry campaign. Wednesday, April 19 (DOY 109): The fourth science archive delivery, scheduled for April 1, has gone very well with most instrument teams delivering earlier than the scheduled due date. The next science archive delivery is scheduled for July 1. A member of the Visual and Infrared Mapping Spectrometer (VIMS) instrument team gave a talk today to the flight team on "Saturn and Titan Revealed: New Infrared Views of Hidden Clouds, Dynamics, and Chemistry from Cassini/VIMS" Part 1 of the S20 background sequence was sent to the spacecraft today at 109T22:06:00. The sequence's registration and activation have been confirmed. Part two will go up on May 11 and begin execution on May 13. Extended Mission Report: Science Planning and the instrument teams are working on defining a set of evaluation metrics for use in selection of an extended mission tour. Some of the metrics suggested include the total number of Titan flybys, number of Titan flybys per year, delta-V left over at end of a 2-year tour, delta-V per flyby, plot of the distribution of closest approach latitudes/longitudes, solar occultation latitude distribution, Radio Science occultation latitude distribution, plots of ground tracks with altitude, plots of ground tracks with phase, overlap between surface images, plot of phase vs. altitude, mid-tail region, Titan tail passages, and number of Titan flybys while Titan is in Saturn's shadow. As you can see from this partial list, balancing science priorities and selecting a tour is not an easy task. 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.
