From: Jet Propulsion Laboratory
Posted: Thursday, December 20, 2012
Cassini is orbiting Saturn with a period of 13.3 days and inclined 53 degrees from the equatorial plane. The most recent spacecraft tracking and telemetry data were collected on Dec. 19 by the Deep Space Network's 70 meter Station 14 at Goldstone, California. Except for some science instrument issues described in previous reports, the spacecraft continues to be in an excellent state of health with all of its subsystems operating 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/ .
Cassini's Attitude and Articulation Control Subsystem (AACS) flight computers were commanded to run new FSW this week. Updates to Flight Software (FSW) have been infrequent during the mission; beyond the software design task, each update requires extensive ground testing and execution of multi-day installation procedures.
Wednesday, Dec. 12 (DOY 347)
The Imaging Science Subsystem (ISS) made an observation in the ring "propeller" tracking campaign (more on these may be found at http://go.usa.gov/YyGR), followed by an observation in the Satellite Orbit campaign. ISS then made a five-hour observation at low-phase illumination of the kilometer-size moon Aegaeon, which is embedded in the G ring.
Cassini's Reaction Wheel Assemblies (RWAs) were spun down and the spacecraft was switched to thruster control in preparation for the AACS flight computer swap. Real time commanding procedures then put AACS flight computer (AFC)-A in control of the spacecraft running the new version A8.9.0 AACS FSW.
Thursday, Dec. 13 (DOY 348)
Magnetospheric and Plasma Science data remained active while Cassini maintained an Earth-pointed attitude. The flight team carried out procedures that loaded the backup AFC-B with the new version of FSW from the solid state recorder.
A surface map of Saturn's atmosphere-shrouded moon Titan released today identifies the locations of mountains that have been named. By convention the International Astronomical Union uses names of mountains in Middle-Earth from the fantasy novels by J.R.R. Tolkien. It may be seen here: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4702 .
Friday, Dec. 14 (DOY 349)
AACS was commanded back to RWA control. This marked the end of the FSW installation procedures, which were executed without incident.
The Composite Infrared Spectrometer (CIRS) decontamination heater #1 power switch tripped, likely because a galactic cosmic ray happened to hit the Solid-State Power Switch (SSPS). The heater switch had been in the off state, so there was no effect. The on-board fault-protection routine set it from "tripped" back to its "off" state. This was the 35th SSPS-trip event in flight.
Saturday, Dec. 15 (DOY 350)
Going back to RWA control, the spacecraft pointed the optical remote-sensing instruments toward Titan and began a 29.5 hour observation in the long-range monitoring campaign. ISS, CIRS, and the Visible and Infrared Mapping Spectrometer (VIMS) acquired data from around a million kilometers away. Another Titan observation took place on Monday.
Sunday, Dec. 16 (DOY 351)
Cassini passed through apoapsis, having coasted "up" to 1.7 million kilometers from the planet and slowing to 10,903 kilometers per hour relative to Saturn. This marked the beginning of Cassini's 177th orbit.
Monday, Dec. 17 (DOY 352)
The Magnetometer Subsystem carried out a calibration by rolling the spacecraft about its Z axis while Cassini was communicating with the Deep Space Network. CIRS then started a 25 hour mapping observation of Saturn in the mid-infrared.
The Navigation team delivered a trajectory prediction in support of a Radio Science observation that will take place January 4-5.
An image from the Titan Monitoring Campaign illustrates how Cassini's highly inclined orbits afford excellent opportunities to study how Titan's south polar vortex has been developing. It may be seen at this URL: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4701 .
Tuesday Dec. 18 (DOY 353)
The Navigation team used the ISS narrow-angle camera to carry out optical navigation observations of Saturn's satellite Mimas against background stars. ISS then made an hour's worth of observations in the satellite orbit campaign, looking near Saturn to improve knowledge of small satellites' orbits or make new discoveries. The Ultraviolet Imaging Spectrograph (UVIS) watched the middle star in Orion's belt, Epsilon Orionis, as Saturn's moon Rhea passed nearby; the purpose was to look for evidence of any exosphere made of volatiles from Rhea. Finally, with VIMS riding along, ISS observed Saturn's F ring for nearly twelve hours to create a movie.
The Project released a mosaic made up of 60 images taken while the spacecraft was in Saturn's shadow. It shows an astounding and rare view of the backlit planet and rings. "A Splendor Seldom Seen" may be seen here: http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20121218/
Visit the JPL Cassini home page for more information about the Cassini Project: http://saturn.jpl.nasa.gov/
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