From: Jet Propulsion Laboratory
Posted: Sunday, February 26, 2012
The most recent spacecraft tracking and telemetry data in this reporting period were acquired on Feb. 21 from the Canberra, Australia, Deep Space Network 70 meter Station 43. The Cassini spacecraft is in an excellent state of health. All subsystems are operating normally except for the issues being worked with the Cassini Plasma Spectrometer and the Ultrastable Oscillator. 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/.
The highlight for this week was the flyby of Saturn's largest moon, Titan, on Sunday. Flyby altitude was 3,803 kilometers.
The week included four PIEs -- Pre-Integrated Events. In the first two, the Imaging Science Subsystem (ISS) conducted Enceladus plume observations. In second pair, the Visual and Infrared Mapping Spectrometer (VIMS) observed two Saturn stellar occultations, acquiring spectral data while Cassini's motion caused the distant stars to go behind Saturn's upper atmosphere.
Wednesday, Feb.15 (DOY 046)
An Engineering Activities Review was held today for the S75 background sequence which is currently in development.
Thursday, Feb. 16 (DOY 047)
ISS, VIMS, and the Composite Infrared Spectrometer (CIRS) performed another observation in the Titan monitoring campaign. CIRS then observed Saturn for 12 hours to measure oxygen compounds (H2O and CO2) in the stratosphere.
Orbit Trim Maneuver 310, the T-82 approach maneuver, was commanded to execute during its backup window tonight (Feb. 17 Universal Time). This was a Reaction Control Subsystem (RCS thruster) burn with a duration of 12.88 seconds and delta-V of approximately 0.02 meters per second. The maneuver was done during the backup window because the reaction wheel speed solution was more favorable, and the need for a time of flight bias in the targeting was avoided.
Friday, Feb. 17 (DOY 048)
ISS, CIRS and VIMS made a 19-hour edge-on observation of the E ring at moderate phase illumination.
The main engine cover was deployed to its closed position.
The NASA Engineering and Safety Center (NESC) team, the Cassini Spacecraft Operations Office, and the CAPS team at the Southwest Research Institute in San Antonio have been meeting weekly since November 2011, to discuss the Cassini Plasma Spectrometer (CAPS) and Radioisotope Thermoelectric Generator (RTG) power bus imbalance anomaly. A preliminary assessment was given orally today. Cassini is now in the process of convening a briefing to JPL upper management for next month.
Saturday, Feb. 18 (DOY 049)
On approach to Titan, CIRS measured stratospheric temperatures and chemical species in Titan's atmosphere. ISS had a one-hour unilluminated prime observation primarily for photometry, i.e. measuring Titan's nighttime brightness, while VIMS stared at Titan for global mapping.
Sunday, Feb. 19 (DOY 050)
Titan encounter T-82 took place today.
CIRS performed a wide variety of observations, including limb sounding and mapping of surface and atmospheric temperatures. Far-infrared limb sounding near closest approach reached the most northerly latitude of the Solstice Mission so far, at 75 degrees. This provides insights into the atmospheric circulation in Titan's north polar region as it transitions from spring to summer, and helps search for possible condensates. VIMS rode along to detect clouds, monitoring climatic changes after the equinox.
T-82 was a dusk sector equatorial flyby across Titan's magnetic tail. Similar in geometry, but at a lower altitude than T-78 last September, it enables Cassini to better characterize the magnetotail by sampling it at different radial distances from Titan at a fixed local time.
In addition to scientific investigation of Titan, each targeted Titan flyby also provides an orbital momentum exchange that modifies Cassini's orbit about Saturn according to plan. T-82 reduced Cassini's orbit period from 23.5 days to 17.9 days.
The T-82 page will be populated with data from the encounter, available here: http://saturn.jpl.nasa.gov/mission/flybys/titan20120219/
Monday, Feb. 20 (DOY 051)
Cassini passed through periapse of Saturn Orbit #161 at 68,375 kilometers per hour early today. At this closest point to Saturn, the spacecraft was about 54,000 kilometers outside the F ring.
Cassini turned its High-Gain Antenna toward Earth and downlinked all the T-82 telemetry data in 9.5 hours. Deep Space Station 63 at Madrid, Spain, captured every bit.
The Ultraviolet Imaging Spectrograph (UVIS) was prime for observations of Saturn's aurorae.
Tuesday, Feb. 21 (DOY 052)
The Ion and Neutral Mass Spectrometer (INMS) measured neutral molecules in Saturn's equatorial plane.
The main engine cover was stowed in its open position. This marks the 71st in-flight cycle. During the week, 312 VIMS cubes were generated and distributed, as were 343 ISS images, including one image for optical navigation and 64 for support imaging.
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