Cassini Significant Events 08/08/2012 - 08/14/2012 The most recent spacecraft tracking and telemetry data were collected on Aug.4 by the Deep Space Network's 70 meter Station 63 at Madrid, Spain. Except for the Cassini Plasma Spectrometer, which is off, and the inoperative Ultrastable Oscillator, the Cassini spacecraft is in an excellent state of health with all of its subsystems functioning normally. Information on the present position of the Cassini spacecraft may be found on the "Present Position" page at: http://saturn.jpl.nasa.gov/mission/presentposition/. This week included a busy period around Saturn periapsis with close-in remote-sensing observations and a direct-sensing Radio Science Saturn atmosphere and ring occultation experiment. Wednesday, Aug. 8 (DOY 221) The Ultraviolet Imaging Spectrograph (UVIS) performed an 18 hour system scan, the last in a series to image hydrogen and oxygen. Thursday, Aug. 9 (DOY 222) The Navigation Team took five images for optical navigation purposes. The Imaging Science Subsystem (ISS) then made a 16 hour low-resolution movie of the F ring. Friday, Aug. 10 (DOY 223) RADAR performed a distant Titan Radiometry calibration. The flight team uplinked two files of commands that will adjust telemetry playback rates to accommodate late changes in the Deep Space Network (DSN) tracking schedule. Saturday, Aug. 11 (DOY 224) The Visible and Infrared Mapping Spectrometer (VIMS) observed an occultation of the star Beta Pegasi by the rings. Sunday, Aug. 12 (DOY 225) To execute a Radio Science (RS) occultation experiment without a functioning Ultrastable Oscillator (USO) on board, the DSN uplinked a reference frequency through Saturn's atmosphere. The Radio Science team had adjusted this uplink frequency so that the spacecraft could receive and lock onto it behind the planet's limb, given the Doppler shift that would be induced by refraction in Saturn's atmosphere. The experiment measured vertical profiles of electron density in the ionosphere, and density, pressure, and temperature in the neutral atmosphere. The RS occultation experiment continued through the full ring system to make high resolution radial profiles of ring structure, shedding more light on variability of dynamical ring features such as waves, wakes, edges, gaps, and narrow ringlets. In addition, the experiment made measurements of ring particle sizes, wake orientation, packing fraction, and ring thickness. Following the RS experiment, the Cosmic Dust Analyzer (CDA) measured particle count rates during the ring-plane crossing to extend knowledge of E ring dust configuration. UVIS made a two-hour "exosphere" observation by watching a star in Orion pass close to Saturn's moon Dione to search for volatiles. The Composite Infrared Spectrometer (CIRS), ISS, and VIMS made an observation of the F ring with resolution about five times better than most F ring observations. Monday, Aug. 13 (DOY 226) Cassini passed through Saturn periapsis today, just inside the orbit of Dione, going 50,000 kilometers per hour relative to Saturn. ISS performed a nine-hour search for moonlets in the C ring. Then for 4.5 hours, CIRS made radial scans on the morning and afternoon sides of the lit rings for temperature characterization. UVIS then made a 1.5 hour observation of Mimas to map the ultraviolet albedo as a function of longitude and phase angle. Tuesday, Aug. 14 (DOY 227) ISS, CIRS, and VIMS created an 11 hour medium resolution F ring movie, monitoring time variable structure in the ring. The first three files of Instrument Expanded Block commands were uplinked today that will be used by the S75 background sequence, which begins execution on August 25. The spacecraft confirmed receiving all 6033 commands. |
