From: Jet Propulsion Laboratory
Posted: Friday, August 24, 2012
The most recent spacecraft tracking and telemetry data were collected on Aug. 22 by the Deep Space Network's 70 meter Station 14 in the California desert at Goldstone. Except for the Cassini Plasma Spectrometer, which is off, and the inoperative Ultrastable Oscillator, the Cassini spacecraft is in an excellent state of health with all its subsystems functioning 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/.
Fast-paced activities during the periapsis portion of Cassini's orbit last week gave way to some longer and slower, but still important science observations for this week.
Wednesday, Aug. 15 (DOY 228)
While Saturn was just over one million kilometers from Cassini's telescopes and receding, the Ultraviolet Imaging Spectrograph (UVIS) completed a 16-hour map of the planet's visible hemisphere in the extreme-ultraviolet and far-ultraviolet parts of the spectrum. The Composite Infrared Spectrometer (CIRS) then made an 11-hour observation to map Saturn's atmosphere in the far-infrared.
Thursday, Aug. 16 (DOY 229)
Today the spacecraft turned its high-gain antenna to Earth and downlinked telemetry data to the Deep Space Network (DSN), while receiving commands and navigation signals across interplanetary space. This was one of only three opportunities this week to connect with the DSN. The Magnetospheric and Plasma Science (MAPS) instruments also undertook survey activities today.
The Attitude and Articulation Control Subsystem team performed a Reaction Wheel Assembly (RWA) bias maneuver. While off Earth-point and not being tracked, thrusters stabilized the spacecraft so the RWA speeds could be adjusted. The Cassini Navigation team relies on telemetry data, which is played back later, to estimate the trajectory effects of the small delta-V resulting from the use of thrusters.
An approval meeting was held for the next ten-week command sequence, S75. Representatives from each science instrument team, the Spacecraft Operations team, and other teams involved, gave their concurrence. The S75 command file was given its final check and authorization for uplink.
Seven remaining files of instrument-expanded block commands, which will support S75 execution, were uplinked today. The distant spacecraft confirmed receipt of all 5481 commands.
New versions of maps for Rhea and Mimas were published on the gallery under Cassini Latest Images: http://saturn.jpl.nasa.gov/photos/
Friday, Aug. 17 (DOY 230)
CIRS turned the spacecraft back to Saturn to map its atmosphere in the mid-infrared for 22 contiguous hours.
Saturday, Aug. 18 (DOY 231)
The MAPS instruments took survey data again today. During a DSN communications session using the 70 meter dish at Goldstone, California, a heavy rainstorm interfered with capture of telemetry data for 21 minutes. Since excessive presence of water vapor in the troposphere degrades the quality of microwave links propagating throughout it, the heavy precipitation decreased the signal-to-noise ratio enough to drown out the data.
Sunday, Aug. 19 (DOY 232)
Optical remote-sensing (ORS) instruments participated today in the campaign to monitor Titan's atmosphere at brief yet frequent intervals; Titan was 3.4 million kilometers away. CIRS and the Imaging Science Subsystem (ISS) then traded opportunities to observe Saturn's atmosphere in a joint campaign to measure winds and atmospheric composition.
Monday, Aug. 20 (DOY 233)
The Realtime Operations team uplinked the S75 background sequence today. After a round-trip light time of 2 hours 50 minutes, the spacecraft confirmed successful receipt and storage of all 10,147 individually timed commands. Cassini will begin executing the S75 sequence on Friday.
CIRS and ISS completed a second set of coordinated wind and composition observations.
The image featured today, "Northern Odysseus," examines the huge crater on Saturn's moon Tethys: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4622
Tuesday, Aug. 21 (DOY 234)
Still under the control of the S74 sequence, ISS had the spacecraft turn its ORS instruments back towards Titan again, which was now 3.5 million kilometers away. UVIS then executed another set of slow scans of Saturn's atmosphere.
The Sequence Implementation Process teams are working on S76 and S77, which will go active in November and January respectively.
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