Cassini Significant Events for 05/04/06 - 05/10/06 The most recent spacecraft telemetry was acquired Wednesday, May 10, 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, May 4 (DOY 124): On Wednesday, May 3, the Titan Orbiter Science Team (TOST) held a Titan flexibility workshop to discuss possible changes to future Titan flyby sequences based on the current data. No changes were made to the existing plans. We all know Earth rotates once every 24 hours, but scientists have long had difficulty pinpointing how long a day is on Saturn. The Magnetometer Subsystem (MAG) has, for the first time ever, measured a periodic signal in Saturn's magnetic field, key information to finally understanding the length of a Saturn day and the evolution of this gaseous planet. The latest research suggests a Saturn day is 10 hours, 47 minutes, 6 seconds, plus or minus 40 seconds. That's 8 minutes slower than NASA Voyager results from the early 1980s, and slower than previous estimates from another Cassini instrument. The magnetometer results provide the best estimate of the Saturn day to date, because it can see deep inside Saturn. These Cassini results can be found in the May 4 issue of the journal Nature. For more information link to: http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=656 Science Planning provided updated numbers for the data recovered from the Titan 13 flyby last week. Without the playback recovery plan in place, the science teams would have lost ~2500Mbits out of 3500, or approximately 70% of the TOST segment, almost all of the closest approach data including almost all of the Synthetic Aperture RADAR (SAR), and all of the Ultraviolet Imaging Spectrograph (UVIS) stellar occultation. With the playback recovery plan in place, this was reduced to ~600Mbits of TOST data lost, or approximately 17%, and ~2100Mbits of Cross Discipline (XD) data including Icy Satellite and Rings data. Only the Visual and Infrared Mapping Spectrometer (VIMS) data was saved of the XD set. Of the 600Mbits lost, almost 500Mbits of that was the earliest inbound data of the flyby and only about 100 Mbits were lost from -27 minutes to -12 minutes affecting the start of the SAR swath. NASA, the European Space Agency, and the University of Arizona have released a joint image advisory with two phenomenal movies. The movies show the dramatic descent of the Huygens probe to the surface of Saturn's moon Titan on Jan. 14, 2005. To view the movies and for more information link to: http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=655 Friday, May 5 (DOY 125): Cassini Outreach participated in two National Space Day events on May 4-5. On May 4, over 3,000 students from Washington DC area schools as well as 1,000 NASA Explorer school students and teacher teams attended a Space Day event at Goddard Space Flight Center. On May 5, over 15,000 students and families from the Washington DC and Northern Virginia area attended a Space Day event at the Smithsonian Institution's Udvar-Hazy Aerospace Museum in Washington DC. The Cassini Reading, Writing, and Rings DVD was highlighted at both events. Uplink Operations sent commands to the spacecraft today for a Cosmic Dust Analyzer (CDA) decontamination exercise, and for a real time Reaction Wheel Assembly (RWA) bias to compensate for the cancelled Orbit Trim Maneuver (OTM) #60. Both files are registered on-board the spacecraft and will execute on DOY 128. Sunday, May 7 (DOY 127): OTM-60, originally planned for May 7, was deleted last November along with OTMs 48 and 54. This was done because there were only three DSN tracks between the cleanup and apoapsis maneuvers, delivery errors did not improve after the apoapsis maneuver, and the maneuvers would be difficult to cancel in real time. The delta-V cost was about 0.8 m/sec. Monday, May 8 (DOY 128): The CDS Command Loss Timer (CLT) software patch will be uplinked beginning today and concluding Wednesday. The Science Operations Plan Update kickoff meeting for S23 was held today. The process runs for five weeks and will conclude on June 9. A very cool panorama of Huygens descending onto the surface of Titan is Astronomy Picture of the Day today. Tuesday, May 9 (DOY 129): On Tuesday, May 9, an Enceladus Plume Debris working group held its first meeting. The primary goal of this group is to characterize the Enceladus plumes so that the Rev 61 flyby can be designed so as to not present a hazard to the spacecraft. The work of this group is also important for creation and analysis of possible extended mission tours. The group needs to develop a dust and gas engineering model that can be incorporated into Mission Planning and Navigation software for planning flyby scenarios. Wednesday, May 10 (DOY 130): The Navigation Team has converged the orbit solution after OTM-059 to the point where it is clear that OTM-061 is a required maneuver with no option for cancellation. About a 20 km correction is needed to achieve the desired flyby for Titan 14. The current orbit determination solution uncertainty is less than 2 km and stable. Further, canceling OTM-061 would increase the total delta-V by about 9 m/s. OTM-061 will be targeted to the reference trajectory flyby point. Since this maneuver will bring us back to the reference trajectory, no update to the Radio Science Subsystem Inertial Vector Definition file, built before the S20 uplink, will be required. The CDS CLT software patch uplink activity was successfully completed today. This patch corrects a code error found last September that was discovered when the timer was set back for OTM-31, resulting in data loss for the Titan 7 flyby. A temporary patch to restore normal operations was issued at that time; this patch fixes the code. Since the Titan 15 to Titan 16 segment is very similar to the segments where Navigation recommended deletion of OTMs 48, 54 and 60, Navigation has now recommended the deletion of OTM-066. Program Management has concurred. In addition to reducing the number of maneuvers by one, the deletion eliminates work on the preceding weekend and saves about 0.15 m/s in the mean. The option to execute the maneuver and its backup on July 10 and 11 will be maintained. 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. --- To unsubscribe from Cassini Spacecraft Updates, send a message to leave-cassini-@xxxxxxxxxxxxxxxxx --- Visit the JPL Cassini home page for more information about the Cassini Project: <http://saturn.jpl.nasa.gov/>
