From: Jet Propulsion Laboratory
Posted: Sunday, June 3, 2012
The most recent spacecraft tracking and telemetry data were collected on May 30 by the Deep Space Network's 34 meter Station 15 at Goldstone, California. Aside from the Ultrastable Oscillator (see the Jan. 5, 2012 Significant Events), the Cassini spacecraft is in an excellent state of health with all its subsystems operating 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/.
Cassini began a year-long phase, starting with the Titan flyby on May 22, during which Titan flybys will continue to increase the spacecraft's orbital inclination. Periapses will continue coming about as close to Saturn as the broad E ring. This plan is designed to provide opportunities for ring occultation experiments by Radio Science and the Ultraviolet Imaging Spectrograph (UVIS), as well as optical remote sensing observations of the rings.
The Imaging Science Subsystem (ISS) performed three observations in the ongoing Satellite Orbit Campaign this week, measuring positions of small satellites to improve knowledge of their orbits. ISS, the Composite Infrared Spectrometer (CIRS), and the Visible and Infrared Mapping Spectrometer (VIMS) performed two observations in the Titan monitoring campaign.
Negotiations to schedule Deep Space Network (DSN) antennas to support Cassini's S74 sequence, which goes active June 18, are proving difficult due to contentions related to Mars Science Laboratory's requirements for support during atmospheric entry, descent, landing, and initial surface operations early this August.
Wednesday, May 23 (DOY 144)
The Navigation Team took five images for optical navigation purposes.
ISS, CIRS, UVIS and VIMS performed a joint observation of the faint D and G rings at low phase angle.
Thursday, May 24 (DOY 145)
The Cosmic Dust Analyzer (CDA) performed a 5 hour measurement of interstellar dust.
Using the Automated Sequence Processor, the Cassini Plasma Spectrometer team sent commands that reconfigured their ion beam spectrometer settings to adapt the instrument to current environmental conditions.
ISS and VIMS telemetry processing halted because of erroneously set flags in data from the DSN regarding earth-receive times. A labor-intensive workaround was devised so that processing can continue while this ground-based anomaly is resolved. The Instrument Operations team initiated Incident-Surprise-Anomaly report (ISA) #52211 to document the problem.
Friday, May 25 (DOY 146)
ISS observed the star Vega for 15 hours to perform a photometric calibration.
Saturday, May 26 (DOY 147)
CDA performed a 13.5 hour interstellar dust observation.
Sunday, May 27 (DOY 148)
Station 25, one of the DSN's 34 meter diameter antennas at Goldstone, California, participated in an Operations Readiness Test (ORT) preparing for the Radio Science ring and atmosphere occultation experiment on June 4.
The Magnetometer Team performed an instrument calibration by rolling the spacecraft about its Z-axis during DSN communications with the high-gain antenna pointed to Earth.
Monday, May 28 (DOY 149)
Cassini passed apoapsis at about 2.3 million kilometers from Saturn, having slowed to 5,771 kilometers per hour relative to the planet.
CDA took advantage of the spacecraft's distance from Saturn to perform another 13.5 hour interstellar dust observation.
An image titled "Splitting Titan" was featured on the Cassini website, illustrating seasonal atmospheric changes in Titan's northern and southern hemispheres. The image may be seen at: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4536
Tuesday, May 29 (DOY 150)
ISS spent 11 hours observing the irregular moon Ymir. The tiny dark body is in a retrograde orbit 23 million kilometers from Saturn.
Station 25 participated in another Radio Science ORT preparing for the June 4 experiment. Orbit Trim Maneuver 324, a 21.4 second maneuver using the main engine, was performed just before midnight, targeting to the Titan encounter on June 7. It provided a delta-V of 3.71 m/s.
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