Cassini Significant Events for 04/25/07 - 05/01/07 The most recent spacecraft telemetry was acquired on Tuesday, May 1, from the Madrid tracking complex. 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" web page located at http://saturn.jpl.nasa.gov/operations/present-position.cfm. Wednesday, April 25 (DOY 115): The Spacecraft Operations Office hosted a presentation to interested members of the flight team on "Estimated Tumbling Densities for All Low- altitude Titan Flybys in the Extended Mission." The presentation was given by personnel from the Attitude and Articulation Control Subsystem, with the results to be used in the determination of minimum safe flyby altitudes. Saturn's iconic image as a ringed planet is both the symbol and the product of scientific discovery. As technology advances, each closer view of the planet has exposed new and unexpected features. At a program of the winter/spring 2007 Earnest C. Watson Lecture Series, the Cassini Project scientist described some of the findings that have changed our understanding of the diverse rings and moons of Saturn, and have yielded insight into the early history of Earth and our solar system. The lecture, "Cassini- Huygens at Saturn: Discovery of New Worlds, Some Familiar and Some Alien," was presented in Beckman Auditorium on the Caltech campus in Pasadena, CA. Caltech has offered the Watson Lecture Series since 1922, when the late Caltech physicist Earnest Watson conceived it as a way to explain science to the local community. Thursday, April 26 (DOY 116): Mission Planning has released a Consumables Report Update showing consumables usage through Feb. 17, 2007, the end of S27, and predicted usage out to Oct. 31, 2007, the end of S34. All consumables usage is running at or in some cases slightly below the expected usage rate. Prior to April 1997, the flight team assembled a list of instrument and spacecraft consumables to be tracked. Since launch on Oct. 15, 1997, Mission Planning has updated these numbers, verified whether the list to be tracked is still complete, obtained numbers for early flight operations, and obtained an estimate of the intended future use of these items to the end of the prime mission. Consumable Report Updates are generated periodically to allow visibility into the predicted end of prime mission and extended mission margins. The Titan 29 (T29) flyby occurred today at an altitude of 980 km with Cassini traveling at 6.2 km/sec. Leading up to the encounter, the Optical Remote Sensing instruments took turns capturing Titan mosaics. For the flyby using Synthetic Aperture Radar (SAR), scatterometry, and altimetry, the RADAR instrument imaged additional regions near Titan's north pole in an area nicknamed the "black sea." The radar coverage crossed over four previous radar swaths and filled in more of the gaps in the coverage of that area. In addition, the Composite Infrared Spectrometer observed the lit and dark sides of Titan, looking for hot spots and lightning. For more information and a PDF of the Mission Description of this flyby link to: http://saturn.jpl.nasa.gov/news/events/titan20070426/index.cfm Today marks the 9th anniversary of the Cassini Venus 1 flyby in April of 1998. Friday, April 27 (DOY 117): The S31 sequence development team has reached that point in the process where it is determined if any part of the sequence should be tested prior to execution on board the spacecraft. After discussion with some of the instrument teams and Spacecraft Operations (SCO), it was decided to run simulations in the Integrated Test Laboratory of the Radio Science (RSS) Saturn occultation Live Movable block on DOY 162 and Live Update Block on DOY 178, the Titan 32 flyby on DOY 164, and the SCO gyroscope calibration on DOY 188. Saturday, April 28 (DOY 118): Orbit determination has converged after processing the first tracking pass and the telemetry from the T29 flyby. With this information, Navigation Team members are predicting very little improvement in the orbit estimate after the data from the next tracking pass is processed. Based on today's orbit solution, Orbit Trim Maneuver (OTM) #107 had a magnitude of 0.529 m/s, however the cost of canceling the OTM was only 0.142 m/s. The delta V increase is primarily in OTM #110, the T30 cleanup maneuver. Based on the minimal cancellation cost, the decision was made to cancel OTM-107. Tuesday, May 1 (DOY 121): At the final sequence approval meeting held today, S30 was approved for uplink to the spacecraft. The sequence leads have begun commanding to send up the instrument expanded block files. S30 will go active on-board on May 4. The final development process has begun for S32 An AACS reaction wheel assembly (RWA) friction test for prime wheels 1, 2, and 4 occurred today. For this activity, performed every three months, the RWAs are spun up to 900 rpm in both directions and are timed as they run down to zero. The results were quite positive, especially for wheel #1, which has previously shown signs of increasing friction. The topic at the Mission Planning Forum today was Extended Mission Titan Altitudes. Based on the tumble densities delivered by SCO/AACS/ Propulsion, and the latest atmosphere models delivered to date, the discussion centered on whether to lower the initial 1000 km minimum flyby altitude for extended mission that has been a baseline assumption for the tour designers so far. 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.
