From: Jet Propulsion Laboratory
Posted: Tuesday, June 1, 2010
The most recent spacecraft telemetry was acquired on May 25th from the Deep Space Network tracking complex at Canberra, Australia. 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/mission/presentposition/.
Wednesday, May 19 (DOY 139)
A Cassini feature was made available on the website today highlighting the upcoming Titan T68 flyby. For the details link to: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20100519/
Science this week included a low phase, close range Titan cloud observation, an Iapetus Hill's sphere observation, a star calibration, and an examination of Enceladus to map volatiles, all performed by Imaging Science (ISS). The Cosmic Dust Analyzer led an interstellar dust (ISD) campaign, a unique opportunity to characterize ISD with Cassini in the outer solar system in 2010, 2011, and 2012. The objective was to measure 100 ISD grains, including 10 with compositional information. The Cassini Plasma Spectrometer (CAPS) led the Magnetosphere and Plasma Science instruments in a solar wind aurora observation. RADAR performed a Radiometric Microwave Sources Calibration, and the Visual and Infrared Mapping Spectrometer (VIMS) performed a stellar calibration utilizing three stars.
Thursday, May 20 (DOY 140)
The S60 sequence leads have reported that Planet-C launched today, so there are no impacts to Cassini DSN station allocations. The telemetry overlay file will not be uplinked, as we will retain DSS-15 on DOY 141-142.
On May 20, Cassini flew by Titan at an altitude of 1,400 kilometers and a speed of 5.9 km/sec. The latitude at closest approach was 49 degrees S. T68 was the fifth Titan flyby of the Cassini mission that was devoted to gravity science. There are two related goals for gravity science flybys at Titan: measuring the fluid and dynamic Love number of Titan and determining Titan's geoid. The determination of the Love number is the only way to find out with confidence whether Titan has an internal liquid ocean. The determination of the geoid is crucial to understanding the internal structure of Titan through correlative analysis of the gravity and RADAR radius data. The observation was covered by beam wave guide (BWG) antennas at all three complexes starting with Madrid's DSS-55, followed by Goldstone's DSS-25, and ending with Canberra's DSS-34. Special unramped uplink predicts were used to improve the data quality. It was a successful observation with almost 17 hours of continuous coherent data acquired.
For this flyby the Composite Infrared Spectrometer (CIRS) took advantage of the furthest south ground track of the extended mission at 80 deg S to observe temperature and composition profiles. ISS rode along with CIRS to track clouds and continued to monitor clouds and their evolution for an extra day after the Titan encounter. The Ultraviolet Imaging Spectrograph (UVIS) obtained an image cube of Titan's atmosphere at extreme and far ultraviolet wavelengths.
The Magnetometer explored the south lobe of Titan's magnetic tail, close to the moon. The Magnetospheric Imaging Instrument measured energetic ion and electron energy input to the atmosphere, and Radio and Plasma Wave Science (RPWS) measured thermal plasmas in Titan's ionosphere and surrounding environment, searched for lightning in Titan's atmosphere, and investigated the interaction of Titan with Saturn's magnetosphere.
Friday, May 21 (DOY 141)
Spacecraft Operations personnel were kept busy Friday evening as they attempted to uplink the command file for maneuver #248. The transmitter at DSS 15 had difficulties and was late locking up, and then it experienced a power failure. Later DSS 15 went to stow due to high winds. The winds kept coming and going so eventually DSS-26 was brought on for additional support. Kudos to the persistence of the folks out at Goldstone as the maneuver, due to execute on Sunday, was successfully uplinked to the spacecraft.
The first Y-thruster bias to be performed as part of the normal sequence development process and executed through the background sequence occurred today. All went well.
Sunday, May 23 (DOY 143)
Orbit Trim Maneuver (OTM) #248 was performed today. This was the cleanup maneuver from the Enceladus 10 and Titan 68 encounters on May 18 and 19. The main engine burn began at 4:30 AM PDT. Telemetry immediately after the maneuver showed a burn duration of 4.94 seconds, giving a delta-V of 0.84 m/s. All subsystems reported nominal performance after the maneuver.
Monday, May 24 (DOY 144)
The Science Forum for S64 was held today. Topics included an overview of the science planned for this sequence followed by highlights, unique activities, and highest priority observations as described by the Target Working Team (TWT) and Orbiter Science Team (OST) leads.
Tuesday, May 25 (DOY 145)
A presentation was given today at the Mission Planning Forum on a new technique for applying Reed-Solomon decoding to the downlink data stream to attain a 1-2dB improvement in performance. It could increase downlink data rates across the board if this technique is validated and used.
The monthly Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference for May occurred today. The topic: Saturn's Strangest Ring. The presentation is available on the website: http://saturn.jpl.nasa.gov/video/products/MultimediaProductsCharm/
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