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NASA Cassini Significant Events for 11/25/08 - 12/02/08

Status Report From: Jet Propulsion Laboratory
Posted: Monday, December 8, 2008

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The most recent spacecraft telemetry was acquired on Dec. 2 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/operations/present-position.cfm.

Tuesday, Nov. 25 (DOY 330):

At the Preliminary Navigation review today for Orbit Trim Maneuver (OTM) 174, it was demonstrated that the delivery errors from OTM-173 could be cleaned up more efficiently with OTM175 at ~80 mm/s than with OTM-174 at ~280 mm/s. Costs downstream of the Titan 48 flyby are also lower if the correction is made with OTM-175. The Navigation team expects to save approximately 2.1 m/s by performing OTM-175 instead of OTM-174. As an added benefit, cancellation of OTM-174 means the maneuver team does not have to work on Thanksgiving Day. Therefore, OTM-174 is canceled

S48 began its final sequence development process when it completed the Science Operations Plan process last Friday and was handed off from Science Planning to Uplink Operations at the S48 kick-off meeting today.

The first science activity today was a Composite Infrared Spectrometer (CIRS) observation of the lit side of Saturn's rings. Then, after a 9-hour downlink, Imaging Science (ISS) turned toward Titan to monitor the formation of any clouds in the atmosphere. The Cassini Plasma Spectrometer (CAPS) then pointed the spacecraft for the Magnetospheric and Plasma Science (MAPS) instruments to survey the magnetosphere.

The topic at the Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference for November was "Enceladus: Results from Recent Cassini Flybys of the Active Moon".

Wednesday, Nov. 26 (DOY 331):

Today ISS took images of the rings for a period of just over 10 hours in order to monitor the rings at low phase angles and to search for and understand the formation of spokes in the rings

An encounter strategy meeting was held today to cover the period between Dec. 5 and Dec. 21, Titan flybys T48 and T49, and maneuvers 176-178.

The S45 sequence concluded and S46 began execution today at 2008-331T11:14 PST. The sequence will run for 44 days and conclude on Jan. 9, 2009. During that time there will be two targeted encounters of Titan and three non-targeted flybys - two of Calypso and one of Enceladus. Six OTMs are scheduled, numbered 174 through 179. The sequence was large enough to necessitate splitting it into two parts. Part two will begin execution on Dec. 23.

Thursday, Nov. 27 (DOY 332):

Commands sent to the spacecraft today included the S46 DOY-337 Enceladus Live Inertial Vector Propagator (IVP) Update and a reaction wheel bias for the OTM-174 backup pass on DOY-333.

As DOY 332 began, ISS was scanning the rings using a variety of its filters to study color variations across Saturn's rings. Following this, CIRS undertook an 8.5-hour observation of Saturn to determine the distribution of water and carbon dioxide in the Saturnian atmosphere as a function of latitude. The MAPS teams, led by CAPS, surveyed the magnetosphere before ISS studied Saturn's smallest satellites. The day's science activities concluded with an Ultraviolet Imaging Spectrograph (UVIS) observation of a stellar occultation by the rings.

Friday, Nov. 28 (DOY 333):

The Saturn Orbit_94_95 segment kicked off today with a Titan monitoring campaign observation followed by ISS imaging of small satellites. The bulk of the day was dedicated to a UVIS Extreme Ultraviolet / Far Ultraviolet observation that was composed of several slow scans across Saturn's visible hemisphere to form spectral images.

The Solid State Power Switch (SSPS) for the backup monopropellant driver (MPD-B) transitioned from OFF to TRIPPED today between 2008-334T16:35:14 and 16:36:18 (SCET)). System Fault Protection (SFP) detected the trip and responded by commanding the switch OFF. This driver was not in use at the time and the spacecraft was nominal following this action. The CDS team will clear the response counter sometime later this week. This is trip #26 since launch and the first one on this particular switch. The last trip occurred during S39 on March 27, 2008.

Monday, Dec. 1 (DOY 336):

High priority science activities in S49 were discussed at the Science Forum today. The purpose of the presentation was to inform Science Planning and Uplink Operations team members of important activities that will be executing during that sequence.

Orbit Trim Maneuver (OTM) #175 was performed today. This is the approach maneuver setting up for the Titan 48 encounter on Dec. 5. The reaction control subsystem (RCS) burn began at 2:14 PM PDT. Telemetry immediately after the maneuver showed the burn duration was 57.5 seconds, giving a delta-V of 0.069 m/s. All subsystems reported nominal performance after the maneuver.

After the OTM-175 maneuver was uplinked to the spacecraft, Uplink Operations sent commands to perform an RCS transition in support of a Radio and Plasma Wave Science (RPWS) Whistler observation scheduled to execute tomorrow over the OTM backup pass.

The Visual and Infrared Mapping Spectrometer (VIMS), with other Optical Remote Sensing (ORS) riders, joined with RADAR to image Saturn's north polar region. The ORS teams were looking at atmospheric dynamics before the spacecraft turned and RADAR covered the same territory.

Tuesday, Dec. 2 (DOY 337):

Non-targeted flybys of Enceladus and Calypso occurred today.

Uplink Operations sent two sets of activities to the spacecraft today. First was a verification file due to execute tomorrow. It will re-load the Ion and Neutral Mass Spectrometer (INMS) Instrument Expanded Block files to the instrument and verify the operation before the Titan 48 INMS science observations begin. Next was the first of two DSN tests of Radio Science Ka-band on_off requested by the DSN. The second test will be on DOY 357.

As the spacecraft approached periapsis, CAPS took over prime pointing during the MAPS campaign to observe Saturn's auroral magnetosphere and Saturn Kilometric Radiation source region. ISS and the other ORS teams took a quick look at Enceladus, and ISS finished the day's prime observations with a wide-angle camera movie of Saturn's aurora.

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

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