NASA Cassini Significant Events 12/21/11 – 1/3/12

The most recent spacecraft telemetry was acquired on January 3 from the Deep Space Network tracking complex at Canberra, Australia. The Cassini spacecraft is in an excellent state of health and with the exception of the CAPS instrument being powered off, 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, Dec. 21 (DOY 355)

Science observations over the past two weeks included a series of observations in the Titan monitoring campaign by the Imaging Science (ISS), the Composite Infrared Spectrometer (CIRS), and the Visual and Infrared Mapping Spectrometer (VIMS). ISS also performed a number of astrometric observations of some of Saturn’s small moons, as well as a 15 hour observation of the outer irregular moon Suttungr. The Ultraviolet Imaging Spectrograph (UVIS) performed two long slow scans of the inner magnetosphere to map hydrogen, and also observed Saturn’s aurora for 11 hours. The Magnetometer performed a 7 hour calibration while the spacecraft rolled about its X-axis. CIRS completed a 23 hour mid-infrared (mid-IR) map of Saturn to determine upper troposphere and tropopause temperature, followed by a 13 hour interstellar dust observation performed by the Cosmic Dust Analyzer (CDA). Later, CIRS performed a 12 hour observation of Saturn in order to measure oxygen compounds (H2O, CO2) in the stratosphere.

Thursday, Dec. 22 (DOY 356)

A feature story called “NASA’s Cassini Delivers Holiday Treats from Saturn” is available on the Cassini web site. It describes how radio signals from the Cassini spacecraft have delivered a holiday package of images. The pictures, from Cassini’s imaging team, show Saturn’s largest, most colorful ornament, Titan, and other icy baubles in orbit around the planet. For images and more information on this subject, link to:
http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20111222/ .

Orbit Trim Maneuver (OTM) #304 was performed today. This was the apoapsis maneuver setting up for the Titan 80 encounter on January 2. The Reaction Control Subsystem (RCS) burn began at 3:14 PM PST. Telemetry immediately after the maneuver showed a burn duration of 10.125 seconds, giving a delta-V of 0.0164 m/s. All subsystems reported normal performance after the maneuver.

An encounter strategy meeting was held today to cover the period between Jan. 2 and Jan. 30, Titan flybys T80 and T81, and maneuver OTM-306 in S71.

A Delivery Coordination Meeting for the Instrument Operations (IO) /Multi-Mission Image Processing Laboratory (MIPL) ground software delivery CAS D40 took place today. This latest version included multi-mission updates, enhancements and new capabilities for the Cassini Solstice mission, bug fixes, and documentation updates which are referenced in approved engineering change request (ECR) 112079. This delivery transitioned smoothly to operations on Dec. 23.

Friday, Dec. 23 (DOY 357)

No signal was detected from the spacecraft today at the beginning of track at Deep Space Station (DSS) DSS-43, the Canberra 70 meter station. Additional tracking was obtained at Canberra’s DSS-45 and Goldstone’s DSS-14 to no avail. The 2-way coherent signal was acquired at the one round trip light-time point into the track as usual, indicating it was a spacecraft problem and not a ground system error. Incident Surprise Anomaly (ISA) #50901 and Discrepancy Report (DR) C108400 were submitted to document this spacecraft anomaly. Commands were sent on Dec. 25 to inhibit the ultra-stable oscillator (USO) and use the auxiliary oscillator as the frequency source for the downlink signal. The spacecraft has operated in this mode for every pass starting on Dec. 27, and telemetry is being received for entire passes again. Data loss was limited to two round-trip light time periods. Analysis of the problem has been delayed because of the holidays with many of the key engineers being unavailable, but it is now well underway.

A feature story called “Cassini Top Images of 2011” is available on the Cassini web site. It showcases the Cassini scientists’ picks of the top images from 2011 with many close-up views of Saturn and its storm. For images and more information on this subject, link to:
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20111223/ .

Saturday, Dec. 24 (DOY 358)

The IO/ISS team has completed further analysis of recent memory readouts of the error/mark table and heap/stack registers. The recent machine error (ISA-50585) was discovered to have been caused by a Bus Interface Unit (BIU) memory issue, which has been observed in the past.

Monday, Dec. 26 (DOY 360)

An image of a raging storm system on Saturn was Astronomy Picture of the Day today. It is available at:
http://apod.nasa.gov/apod/ap111226.html .

Tuesday, Dec. 27 (DOY 361)

The Attitude and Articulation Control Subsystem (AACS) Periodic Engineering Maintenance was completed today. This activity, performed approximately once every three months, spins up the backup reaction wheel assembly for lubrication purposes and exercises the back-up engine gimbal actuator.

Wednesday, Dec. 28 (DOY 362)

A glimpse at the year ahead is now available on the “Saturn Tour Dates” page. For details on the subject link to:
http://saturn.jpl.nasa.gov/mission/saturntourdates/ .

Thursday, Dec. 29 (DOY 363)

Earlier this month, the U.S. Cassini Scientist for a Day winners, finalists, and honorable mention winners were officially notified, and their names were posted on the Cassini website. The winners and their photos and essays are now posted on the “Meet the Winners” page at:
http://saturn.jpl.nasa.gov/education/scientistforaday10thedition/winners2011/ .

Monday, January 2 (DOY 2)

Cassini encountered Titan at an altitude of 29,415 kilometers and a speed of 5.5 km/sec today. On this high-altitude encounter, the imaging science subsystem (ISS) performed high-resolution observations around closest-approach along the anti-Saturnian and trailing hemispheres at mid- to high southern latitudes. This is one of ISS’s so-called “10-pointer” flybys, i.e. one of the two scientifically most significant Titan flybys for ISS during the Solstice mission. For more information on the flyby, link to:
http://saturn.jpl.nasa.gov/mission/flybys/titan20120102/ .