From: Jet Propulsion Laboratory
Posted: Friday, May 4, 2012
The most recent spacecraft tracking and telemetry data were collected on May 2 using the Deep Space Network's 34 meter high-efficiency Station 34 at Canberra, Australia. Aside from the issue in work with the Ultrastable Oscillator (see the January 5, 2012 Significant Events), the Cassini spacecraft is in an excellent state of health. Its subsystems are operating normally as the spacecraft orbits Saturn, nearly in the equatorial plane, once every 17.8 days. 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/.
This week's events included preparations for the Enceladus E-19 targeted flyby on May 2, which will bring the spacecraft to within 74 kilometers of the icy satellite and make measurements of its gravity field. More information on E-19 may be found here: http://saturn.jpl.nasa.gov/mission/flybys/enceladus20120502/
On the ground, Cassini flight team members made progress working on science observation plans for sequences S74, which goes active in June, S75 (August), S76 (November), and S77 (January 2013).
Wednesday, April 25 (DOY 116)
The Spacecraft Operations Office held an Engineering Activities Review for the S76 command sequence. The Radio Science Support team held a meeting with members of the DSN and Realtime Operations teams to finalize operations for the E-19 gravity observation.
Thursday, April 26 (DOY 117)
A 34 meter diameter Deep Space Network (DSN) station in Canberra, Australia, participated in an Operational Readiness Test, preparing for the E-19 realtime Radio Science gravity measurement during closest approach on May 2.
A news release titled, "Cassini Finds Saturn Moon Has Planet-Like Qualities" describes new findings about Saturn's outer, retrograde moon Phoebe. It may be viewed here: http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20120426/
Friday, April 27 (DOY 118)
The Attitude and Articulation Control (AACS) team performed a reaction-wheel assembly (RWA) bias maneuver, stabilizing the spacecraft via thrusters and setting the RWAs to the required speeds while the DSN was tracking the spacecraft. AACS also performed a calibration of the spacecraft's backup inertial reference unit (gyros). These calibrations are performed about once per year and require rotating the spacecraft about its X, Y and Z axes.
Saturday, April 28 (DOY 119)
ISS performed another observation in the Satellite Orbit Campaign. VIMS performed a Saturn storm watch observation.
Commands were sent to the spacecraft that were time-tagged to power the Cosmic Dust Analyzer (CDA) back on just prior to the E-19 flyby. Additional commands were sent to do a live update within the AACS Inertial Vector Propagator to refine pointing information on the location of Dione, which will be observed during the non-targeted encounter following E-19.
Orbit Trim Maneuver (OTM) 319, the E-19 approach maneuver, operated the Reaction Control Subsystem thrusters for 29.5 seconds, resulting in a delta-V of 0.034 meters per second.
Saturn was the featured attraction at two local Astronomy Day activities attended by Cassini outreach specialists.
Sunday, April 29 (DOY 120)
The DSN provided eight tracking sessions for Cassini using stations in Canberra, Australia, and Goldstone, California this week. There were several small data outages.
Monday, April 30 (DOY 121)
The Ultraviolet Imaging Spectrograph (UVIS) performed a 10 hour observation of Saturn's aurora.
The main engine protective cover was deployed to its closed position.
The Attitude and Articulation Control Subsystem executed an RWA Y-bias maneuver to adjust wheel speeds while Cassini was off Earth point, out of communication.
An image titled "Moon Specks", showing Tethys and Enceladus, is featured here: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4516
Tuesday, May 1 (DOY 122)
ISS observed an irregular outer satellite for nearly 10 hours to gather data for a light curve to give further information on the collisional environment in the outer Saturnian system. VIMS performed a 3-hour solar-port calibration activity. DSN station 25, a 34 meter aperture at Goldstone, California, began a gravity science enhancement observation prior to tomorrow's E-19 flyby. Station 25's X-band (8 GHZ) uplink provided for an X-band and Ka-band (32 GHz) coherent downlink from Cassini. The Doppler data contained in these signals will add to knowledge of Enceladus's gravity field.
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