NASA Cassini Significant Events 03/28/2012 - 04/03/2012

Status Report From: Jet Propulsion Laboratory
Posted: Tuesday, April 10, 2012

image The most recent spacecraft tracking and telemetry data were collected on April 4 using the Deep Space Network's 34 meter Station 15 at Goldstone, California. Aside from the issues in work with the Ultrastable Oscillator (see the Jan. 5, 2012 Significant Events) and the Cosmic Dust Analyzer, the Cassini spacecraft is in an excellent state of health and its subsystems are operating normally. Information on the present position of the Cassini spacecraft may be found on the "Present Position" page at:

Telemetry data from the targeted Enceladus encounter E-17 on March 27 were transmitted 1.3 billion kilometers to Earth on Wednesday; every bit was captured successfully by the Deep Space Network. The Ion and Neutral Mass Spectrometer (INMS) was able to discern variations in CO2 density among the individual gas jets as the spacecraft dove through the Enceladus south polar plume. The Cassini Plasma Spectrometer (CAPS), which was recently powered back on, acquired excellent data in and near the plume, along with the Cosmic Dust Analyzer (CDA) and INMS. A spectacular image of the south polar plume may be seen here, along with images of the icy moons Janus, taken March 27, and Dione, taken March 28:

Wednesday, March 28 (DOY 088)

The Instrument Operations Team and the Multi-mission Image Processing Laboratory expedited processing of Cassini's data, delivering images to the science team and to the raw-image website during the downlink.

Cassini turned to point its high-gain antenna to the icy moon Dione for the RADAR instrument to make scatterometry and radiometry observations of its surface, then the Imaging Science Subsystem (ISS) took images of Dione at a distance of 44,000 kilometers and compiled a nine-frame mosaic showing the side of the moon that faces away from Saturn during its 2.7-day orbit.

ISS made observations in the Titan Monitoring Campaign while the target was about 1.2 million kilometers away. Then ISS conducted a search for possible satellites around Rhea's stable L5 Lagrange point, 60 degrees behind the satellite as it orbits Saturn.

The Attitude and Articulation Control Subsystem (AACS) executed a Reaction Wheel Assembly (RWA) bias maneuver to adjust wheel speeds.

The Realtime Operations Team sent a total of 9,506 "Instrument-Expanded Block" commands to the spacecraft in eight separate files using the Autorad utility for convenience. Every command was properly received and stored on-board. They will be called during execution of the S73 sequence, which begins next week.

The main engine cover was opened to its stowed position; this was the 72nd in-flight cycle of the flexible micro-meteoroid shield.

Thursday, March 29 (DOY 089)

After pointing to Saturn's icy satellite Rhea to do an observation by the Optical Remote-Sensing instruments and a photometric calibration of ISS, Cassini turned to train its optical telescopes on the bright star Alpha Centauri for a 7 hour calibration of the Visual and Infrared Mapping Spectrometer (VIMS).

CDA was turned off, and its replacement heater turned on, by realtime commands after valid science data and instrument engineering data packets unexpectedly stopped coming from the instrument. After a round-trip light time of 2 hours 26 minutes, telemetry indicated that the commands had the desired effect.

Friday, March 30 (DOY 090)

Realtime commands were sent to power CDA back on and its replacement heater off.

VIMS performed another 7 hour calibration using Fomalhaut, one of the brightest stars in the sky.

Orbit Trim Maneuver (OTM)-314, the post-E17 cleanup maneuver, turned the spacecraft and fired the Reaction Control Subsystem thrusters for 133.8 seconds, providing a delta-V of 143.8 mm/s. After the OTM was complete, AACS executed another RWA bias maneuver.

For the 34th time since launch, a Solid-State Power Switch (SSPS) experienced a circuit trip, attributed to being hit by a cosmic ray particle. This time, it set the backup helium latch-valve power circuit from the "off" state to "tripped." An on-board fault-protection routine sensed this and set the line back to "off" with no effect on spacecraft operations. The last SSPS trip occurred about 18 months ago.

Saturday, March 31 (DOY 091)

Cassini rotated to the attitude needed by the Cassini Plasma Spectrometer (CAPS) so it could perform an 11 hour observation of charged particles in its immediate environment. This was followed by a four hour calibration of the instrument's ion beam spectrometer and its ion mass spectrometer.

Sunday, April 01 (DOY 092)

CIRS performed a 20 hour mid-infrared map of Saturn to determine temperatures in the upper troposphere and tropopause.

Saturn and its moons figure prominently in the video "What's Up for April":

Monday, April 02 (DOY 093)

The S73 final sequence integration and validation approval meeting and command approval meeting were held this morning. Later in the day, S73 sequence Part-1 was uplinked. All 6683 of its commands were received and registered on the spacecraft.

CDA performed a 13.5 hour interstellar dust observation today, a few days before the spacecraft reached apoapsis.

The "Hazy Orange Orb" of Saturn's giant moon Titan is featured in this natural-color image today. The north polar hood is clearly visible above Titan's dense atmosphere:

Tuesday, April 03 (DOY 094) ISS, CIRS, and VIMS performed another observation in the Titan Monitoring Campaign, and ISS performed another observation in the Satellite Orbit Campaign. ISS then conducted a 9.5 hour observation of the irregular moon Thrymr, a "rock" about 6 kilometers wide in a very distant, retrograde orbit.

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