News | November 28, 2007
Cassini Significant Events 11/14/07 - 11/27/07
Cassini Significant Events 11/14/07 - 11/27/07
November 29, 2007
(Source: Cassini Project)
Due to the Thanksgiving holiday, this report covers two weeks instead of the usual one week.
The most recent spacecraft telemetry was acquired on Tuesday, Nov. 27, 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" page at:
Wednesday, Nov. 14 (DOY 318):
A member of the Cassini AACS team gave a presentation on "Status of Cassini Reaction Wheels at Launch +10.074 Years" to various levels of JPL management today.
A Delivery Coordination Meeting (DCM) was held addressing two software deliveries. Both are for updated Spacecraft Operations (SCO) ground software tools in order to make them compatible with the new CDS V10 flight software. The first is the Downlink Uplink Coherency Tool (DUCT), which inserts a 5-minute playback pause at the one-way-to-two-way transition in every downlink. This tool was created to automatically pause playback so that no science data is lost during the brief telemetry outage that occurs during this transition. The second is the Assisted Load Format (ALF) tool used with instrument expanded block files.
Today ring science was the focus for Imaging Science, the Magnetospheric and Plasma Science (MAPS) instruments, and RADAR. Probing the rings at wavelengths of 2 centimeters, the goal of the RADAR team is to determine the rings' global properties, as well as image the rings at wavelengths much longer than those used by the ORS suite of instruments.
Thursday, Nov. 15 (DOY 319):
Orbit Trim Maneuver (OTM) #133 was performed today. This is the approach maneuver setting up for the Titan 37 encounter on Nov. 18. The reaction control subsystem (RCS) burn began at 8:14 AM PST. Telemetry immediately after the maneuver showed the burn duration was 50.75 seconds, giving a delta-V of 0.067 m/s, as planned. All subsystems reported nominal performance after the maneuver. For the first time, a reaction wheel bias was performed in the background sequence before the OTM. This was done at the request of the Navigation team to ensure that a bias occurred over that pass regardless of the OTM status.
Friday, Nov. 16 (DOY 320):
The Satellite Orbiter Science Team (SOST) held its first meeting to integrate the Enceladus flybys in the proposed Extended Mission (XM). Meanwhile, XM integration activities continue for the rest of the Target Working Teams.
On DOY 320, Cassini made non-targeted flybys of Rhea and Pandora. Closest approach for Rhea was 91,537 km from the moon. As the spacecraft approached the satellite, the Optical Remote Sensing (ORS) instruments conducted a coordinated campaign to observe Rhea, with the Visual and Infrared Mapping Spectrometer (VIMS), Ultraviolet Imaging Spectrograph (UVIS), and Composite Infrared Spectrometer (CIRS) teams, in turn, controlling the pointing of the spacecraft. Some of the goals of these observations are to constrain the shape of this moon, which has implications for its internal structure and evolutionary history, and to measure the ultraviolet albedo. Following the ORS observations, the Cosmic Dust Analyzer (CDA) began a series of observations, sampling the particles in the vicinity of Rhea as the spacecraft crossed Rhea's orbit. This was followed by a second coordinated Rhea observation campaign by the ORS instruments.
Saturday, Nov. 17 (DOY 321)
Non-targeted flybys occurred today with Pan, Epimetheus, and Calypso.
The first real-time Radio and Plasma Wave Science (RPWS) Whistler event occurred today at ~32 hours prior to T37. "Whistlers" are waves that result from lightning in the clouds of Saturn. Over the last few days, trigger commands have been sent to the instrument in preparation for the event. For this activity, the spacecraft will transition into and out of RCS control during a 9-hour downlink pass.
Sunday, Nov. 18 (DOY 322)
Titan T37 closest approach occurred at 2007-323T00:56:25 Spacecraft Event Time. The spacecraft flew past at 1,000 km altitude, and used 393.6 grams of hydrazine for science pointing and attitude control, within 10% of predict. Owing to the relatively low altitude of the flyby, it was expected that Cassini would pass through Titan's ionosphere. Prior to the flyby, the orbit period was about 24 days, at 5 deg inclination. The encounter reduced the Saturn orbit period to 16 days and increased the inclination to 12.3 degrees, beginning a series of Titan encounters that will increase the inclination to about 75 deg before end of prime mission.
As Cassini made its closest approach to Titan, the Ion and Neutral Mass Spectrometer (INMS) sampled the upper reaches of Titan's atmosphere, measuring composition and thermal structure. This was followed by VIMS observations to perform high resolution mapping of Titan for geology and composition, as well as mapping the limb of Titan and Titan's cloud distribution.
ISS monitored the atmosphere for lightning and aurorae, and obtained data for a series of regional and global scale mosaics. The area imaged in the regional mosaic, northwest of Ederi, is complementary to that area imaged in T35 northeast of Ederi. UVIS obtained spectral images of Titan in the Extreme Ultraviolet and Far Ultraviolet to map the aurora and day glow, to map hydrocarbon absorption, and to measure scattering and absorption by aerosols in the stratosphere. CIRS obtained measurements during this Titan flyby to carry out vertical temperature sounding of Titan's tropopause and stratosphere, and to learn about the distribution of various components of Titan's atmosphere, such as methane, water, carbon monoxide and aerosols.
The MAPS teams undertook an investigation of the large-scale and distant aspects of the interaction between Titan and the magnetosphere. The Magnetometer Subsystem (MAG) compared data taken on this flyby with that taken during T36 to look for temporal variations in the magnetic field in the wake/south polar region. RPWS took advantage of the spacecraft's close wake passage near the southern boundary of the geometric wake.
Tuesday, Nov. 20 (DOY 324)
A member of the Cassini Spacecraft Operations Office flew home for the holiday this week. As part of his vacation, the plan was to give a JPL overview presentation for all students K-12 in Greensburg, KS. The problem was, Greensburg no longer existed. Six months ago, Greensburg was a thriving county seat of 1600 people, block after block of nice houses and businesses. On May 4, 2007, an F5 tornado leveled the town, destroying over 95% of the town's buildings.
In showing the frontier spirit of the town, most folks have moved back - using FEMA trailers - and they decided NOT to disperse the school kids far and wide, but rather to hold school in town, again, in FEMA trailers. In honor of the completion of the first permanent school building, the gym, the show went on! Over two hundred students were given the presentation they were meant to have and were presented with as many NASA goodies as could be sent to them in advance and packed on the plane with the presenter.
Thursday, Nov. 22 (DOY 326):
OTM-134 was performed today. This is the cleanup maneuver from the T37 encounter on Nov. 19. The main engine burn began at 12:14 AM PST. Telemetry immediately after the maneuver showed the burn duration was 7.2 seconds, giving a delta-V of 1.17 m/sec. All subsystems reported nominal performance after the maneuver.
Friday, Nov. 23 (DOY 327):
The MAPS instruments continued their solar wind monitoring campaign, with the Magnetospheric Imaging Instrument (MIMI) pointing the spacecraft during science observation periods. MIMI briefly turned the spacecraft towards Iapetus for ISS and UVIS observations on DOY 328.
Monday, Nov. 26 (DOY 330)
OTM-135 was performed today. This is the apoapsis maneuver setting up for the Titan 38 encounter on Dec. 5. The main engine burn began at 11:59:56 PM PST. Telemetry immediately after the maneuver showed the burn duration was 96.5 seconds, giving a delta-V of 15.75 m/s. All subsystems reported nominal performance after the maneuver.
Navigation delivered the necessary orbit determination files today for the DOY 336-337 Mimas/Epimetheus Live Update process. A kick-off meeting was held today and then participants went off to review the data. So far, inputs from the teams have recommended going with the update. It will be uplinked on Thursday or Friday of this week and begin execution Sunday, Dec. 2.
Science today included Cassini Plasma Spectrometer (CAPS) observations of the dusk-side magnetospheric boundary at a variety of latitudes, a UVIS study of the Saturn aurorae, ISS imaging of Telesto, Janus, Pandora, Methone and Calypso to better determine their orbital characteristics, and observations of the distant satellite Erriapo.
Tuesday, Nov. 27 (DOY 331)
At the Mission Planning Forum today the topics of discussion were 1) New telemetry modes for the proposed extended mission, and 2) Plans for Main Engine Cover operations after the project has exceeded the originally predicted 37 cycles of use.
The final sequence development process for S38 kicked off today. The process will complete mid February next year with execution beginning on Feb. 16. Issues discussed included the status of the currently posted seven S38 waiver requests, the possible loss of the last DSN track in the sequence, and the upcoming effort to re-evaluate the Enceladus custom period with CIRS to possibly submit a sequence change request. In addition, S39 development continued with teams delivering products for the preliminary port.
A Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference was held today. The topic for this month was The Lakes and Seas of Titan: Observations from Cassini RADAR.