From: Jet Propulsion Laboratory
Posted: Monday, February 13, 2012
The most recent spacecraft tracking and telemetry data in this reporting period were acquired on Feb. 8 from the Deep Space Network 70 meter Station 14 at Goldstone, California. The Cassini spacecraft is in an excellent state of health with all subsystems operating normally except for the known issues with the Cassini Plasma Spectrometer and the Ultrastable Oscillator. 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/.
This week's science activities began with multi-instrument observations of Titan from as far as 2.8 million kilometers away, as Cassini continued moving towards apoapse. These activities included a RADAR radiometry observation and a calibration, and observations by the Composite Infrared Spectrometer (CIRS), Imaging Science Subsystem (ISS) and the Visual and Infrared Mapping Spectrometer (VIMS) for atmospheric and cloud monitoring. Following this, the Cosmic Dust Analyzer (CDA) made a 13.5 hour interstellar dust observation.
Later, ISS performed observations of some of Saturn's small inner moons (part of the Satellite Orbit Campaign), including Janus and Polydeuces, to improve understanding of the orbits of these small satellites. This was followed by a 9.5 hour search for Trojan satellites around the L5 Lagrange point, 60 degrees behind Titan in its orbit.
Finally, ISS made some additional observations in the Satellite Orbit Campaign, and then CIRS, ISS and VIMS made an 11 hour Titan observation from a distance of more than 3.6 million kilometers.
Wednesday, Feb. 1 (DOY 032)
Yesterday the second half of the column celebrating the work of Dr. Jean-Pierre Lebreton, who before retiring was the European Space Agency Project Scientist and Mission Manager for the Huygens mission to Titan, was posted to the Cassini web site. See:
Today Deep Space Station 26, a 34 meter Beam Waveguide antenna at Goldstone, performed a monopulse calibration of value to Radio Science Ka-band experiments. The calibration caused unexpected antenna movement and a short loss of Cassini data.
The Reaction Wheel Assembly Bias Optimization Tool identified a segment in the S74 command sequence, which is under construction, that had to be reworked to avoid placing a redundant bias in the Radio Science Enceladus observation keep-out zone. Negotiations for Deep Space Network resource allocations for this sequence have started; the first two days of the ten-week sequence are completed.
Thursday, Feb. 2 (DOY 033)
Orbit Trim Maneuver #308, the Titan 81 cleanup maneuver, was successfully executed today Pacific Time (Feb. 3 Universal Time). With a burn duration of 124.37 seconds on Reaction Control Subsystem thrusters, it provided the spacecraft a delta-V of 0.137 m/sec, targeting Cassini to the T-82 aimpoint. This was the second maneuver designed using the new Monte software, and the first prepared with Maneuver Automation Software v9.2. This version of the software allows the main engine assembly heaters to be powered off for the backup maneuver opportunity, avoiding a thermal cycle.
The Instrument Operations (IO) team and Multi Mission Image Processing Laboratory (MIPL) swapped processes to and from computer hardware requiring patch and firmware upgrades. During this activity, the MIPL database, servers, Cassini Atlas, and MIPL file system were unavailable.
Friday, Feb. 3 (DOY 034)
Nominal IO and MIPL operations resumed.
The Attitude and Articulation Control Subsystem executed a Reaction Wheel Bias maneuver while Cassini was being tracked from Earth following the Orbit Trim Maneuver. While thrusters maintained attitude, the reaction wheel speeds were set to the required values.
On the ground, a new suite of Telemetry Channel Parameter Tables, called Tour-12, has been installed on test workstations, and on one operations workstation for "soak" testing. Plans are to distribute the files to all users next week pending a successful outcome of the testing.
Saturday, Feb. 4 (DOY 035)
JPL conducted a 5-hour training session in partnership with the California Afterschool Network for 60 leaders and site coordinators of San Bernardino Unified School District's "Creative Before and Afterschool Programs for Success" (CAPS). The attendees pursued hands-on activities from the NASA/JPL "Jewel of the Solar System" activity guide on Saturn and Cassini for grades 4 and 5. The workshop was visited by the CAPS leadership.
Monday, Feb. 6 (DOY 037)
A Y-thruster-pair calibration took place today. This annual event allows Navigation and Attitude Control teams to validate the force-balance of the coupled Y-thruster pairs. Navigation will analyze Doppler tracking data as part of the T-81 to T-82 spacecraft ephemeris reconstruction, looking for indications of any unevenness, important because the Y-Bias maneuvers are performed so often. Those maneuvers are described here:
Tuesday, Feb. 7 (DOY 038)
The Radio Science Subsystem Team performed a Radio Frequency Instrument Subsystem Periodic Instrument Maintenance activity today. The spacecraft's Ka-band transmitter was turned on and observed. Normally this kind of activity also measures performance of the Ultrastable Oscillator, but due to the current anomaly only the Auxillary Oscillator was seen.
Seventy-five packages were mailed today to the teachers whose students participated in the Cassini Scientist for a Day essay contest. Each student and teacher received a certificate of participation, and all teachers received a package of Cassini educational materials. Winners, finalists, and honorable mention recipients received special certificates as well. To see the winning essays, visit: http://saturn.jpl.nasa.gov/education/scientistforaday10thedition/winners2011/
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