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NASA Cassini Significant Events for 10/15/08 - 10/21/08

Status Report From: Jet Propulsion Laboratory
Posted: Monday, October 27, 2008

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The most recent spacecraft telemetry was acquired on Oct. 21 from the Deep Space Network tracking complex at Goldstone, California. 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" page at: http://saturn.jpl.nasa.gov/operations/present-position.cfm.

Wednesday, Oct. 15 (DOY 289):

Today the Cassini flight team celebrated the 11th anniversary of launch.

Today was relatively quiet for science activities. The beginning of the day was devoted to completing the long F ring movie started the day before. Afterwards the spacecraft turned toward Earth to downlink science data to Goldstone DSN stations. The day finished with a short Composite Infrared Spectrometer (CIRS) thermal map of the main rings.

The S45 background sequence was radiated to the spacecraft over the Goldstone DSS-15 pass today. Execution will begin on Saturday at 2008-292T20:21 Spacecraft Event Time (SCET).

Thursday, Oct. 16 (DOY 290):

The spacecraft is approaching periapsis and the level of science activity is increasing. This makes sense if you remember that each time the spacecraft reaches periapsis, it is the closest it will be to Saturn for that orbit.

Today CIRS took data for a thermal map of the main rings. The Visual and Infrared Mapping Spectrometer (VIMS) observed the bright star Gamma Crucis as it passed behind rings F through D, and later scanned the shaded portion of the unlit side of the rings. The imaging cameras (ISS) had a short retargetable activity to search for yet-undiscovered moons or ring features, and the Ultraviolet Imaging Spectrograph (UVIS) observed a stellar-ring occultation, this time of a bright ultra-violet star. After the Optical Remote Sensing (ORS) instruments completed their observations, the Magnetospheric and Plasma Science (MAPS) teams observed the auroral magnetosphere and Saturn Kilometric Radiation source region.

Friday, Oct. 17 (DOY 291):

Non-targeted flybys of Palene and Epimetheus occurred today.

Orbit Trim Maneuver (OTM) #168 was performed today. This was a large periapsis maneuver setting up for the Enceladus 6 flyby on Oct. 31, and targeted Titan 46 encounter on Nov. 3. The main engine burn began at 3:34 AM PDT. Telemetry immediately after the maneuver showed the burn duration was 41.7 seconds, giving a delta-V of 7.0 m/s. All subsystems reported nominal performance after the maneuver.

The maneuver was preceded by one of the early Extended Mission Radio Science (RSS) ring occultations spanning a chord of the ring system. For this observation, RSS observed at Ka, X and S band frequencies. An unusually long 14-hour downlink block to accommodate a series of navigation and engineering events followed. Prior to the maneuver, Spacecraft Operations received telemetry confirming that the main engine (ME) cover was open. The ME cover is used to protect the engines from small particulates during ring plane crossings. Once the OTM was complete, a real time Radio and Plasma Wave Science Whistler observation was performed on thrusters during the backup maneuver pass. These observations are designed to obtain wideband evidence of lightning whistlers, would verify the existence of lightning already suspected from Saturn Electrostatic Discharges (SED), and would provide information on the electron density along the field line to the source. The cover was closed again at the end of the pass for a dust hazard that will occur on October 24. This was cycle #49 for the ME cover.

Saturday, Oct. 18 (DOY 292):

The last science activities of the S44 sequence were a small satellite orbit determination campaign by ISS, a CIRS thermal map of the rings, and three optical navigation images for the Navigation team. The spacecraft then turned toward Earth to downlink the remainder of S44 science data before handing off to the next day and next sequence.

The S44 sequence concluded and S45 began execution today at 2008-292T14:44 Pacific Time. The sequence will run for 40 days and conclude on Nov. 26. During that time there will be two targeted encounters of Titan and sixteen non-targeted flybys - two each of Enceladus and Tethys, and one each of Titan, Janus, Pan, Mimas, Methone, Pandora, Daphnis, Atlas, Epimetheus, Polydeuces, Telesto, and Helene. Five OTMs are scheduled, numbered 169 through 173.

Sunday, Oct. 19 (DOY 293):

A non-targeted flyby of Titan occurred today.

The first day of the S45 sequence featured rings observations led by VIMS and CIRS. VIMS made a mosaic of the lit side of the rings while CIRS watched as the star CW Leo, a bright infrared source, passed behind the rings. The Cassini Plasma Spectrometer (CAPS) ended the day with almost two hours of dedicated studies of the Saturnian magnetosphere.

Monday, Oct. 20 (DOY 294):

A beautiful image of Saturn with moons and rings is Astronomy Picture of the Day today. Check it out at: http://antwrp.gsfc.nasa.gov/apod/ap081020.html

Today is the first day of a week-long Cassini Project Science Group meeting. This is the 46th assembly of this group since the project began its early stages of development back in the mid 1980s. This week, Cassini scientists will come to JPL to participate in Saturn, Icy satellite, Titan, Rings, and Magnetospheric working groups, instrument team meetings, and to give status reports to those assembled on work in progress.

Much of the day's science activities involved ISS observations of Mimas, Tethys, Titan and Saturn's small satellites, as well as Saturn's G ring. In addition, UVIS studied the volatiles in the vicinity of Enceladus to determine the nature of the relationship between the very tenuous atmosphere at Enceladus and the plumes emanating from that moon's southern pole. To better study Saturn's magnetosphere, CAPS oriented the spacecraft for MAPS observations for nearly five hours

Tuesday, Oct. 21 (DOY 295): Closing out this week, ISS imaged Saturn's main rings through a combination of its filters to produce high-resolution color scans in addition to continuing campaigns to monitor Saturn's small satellites and its F ring. UVIS performed a two-hour observation of the surface of Dione.

Visit the JPL Cassini home page for more information about the Cassini Project: http://saturn.jpl.nasa.gov/

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