Cassini Significant Events 03/27/2013 – 04/02/2013

Cassini is orbiting Saturn with a twelve-day period in a plane inclined 57 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were collected on April 3 by a 34-meter Deep Space Network station at Canberra, Australia. Except for some science instrument issues described in previous reports, the spacecraft continues to be in an excellent state of health with all of 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/.

Following periapsis passage last week, the geometry was right for a variety of ring observations, which Cassini carried out this week. Optical Remote-sensing (ORS) instruments captured images, movies, temperatures, and spectra. The direct-sensing Cosmic Dust Analyzer (CDA) measured in-situ particles while the spacecraft flew through the E ring. There were stellar occultations during which the ORS instruments used the point source light from distant stars to probe the rings. And the Deep Space Network (DSN) prepared for an upcoming Radio Science ring occultation experiment.

In other news, a web page has been published to provide information about next week's close flyby of Saturn's largest moon Titan, the T-90 encounter: http://saturn.jpl.nasa.gov/mission/flybys/titan20130405/

Wednesday, March 27 (DOY 086)

The Imaging Science Subsystem (ISS) and the Ultraviolet Imaging Spectrograph (UVIS) completed a nineteen-hour observation of the distant retrograde rock Narvi (named after a giant in Norse mythology). ISS then began creating an eleven-hour movie of the F ring.

Thursday, March 28 (DOY 087)

ISS, the Composite Infrared Spectrometer (CIRS) and the Visible and Infrared Mapping Spectrometer (VIMS) performed another observation in the Titan monitoring campaign from 2.5 million kilometers away; another of these occurred on Saturday from a slightly closer range.

Cassini passed through apoapsis, having coasted 1.53 million kilometers from the planet and slowing to 12,415 kilometers per hour relative to Saturn. This marked the beginning of Cassini's orbit #185.

ISS spent 13.5 hours observing the irregular moon Hyrrokkin. Like Narvi, this small object is in a very distant retrograde orbit about Saturn.

Friday, March 29 (DOY 088)

CIRS executed a calibration using the infrared-bright star CW Leonis to map the spatial response of pixels in one of the instrument's focal planes.

A Cassini image capturing three of Saturn's moons was featured as today's Astronomy Picture of the Day. View "Ringside with Rhea" here: http://apod.nasa.gov/apod/ap130329.html

Saturday, March 30 (DOY 089)

A 34-meter diameter DSN station in California participated in an operations readiness test, preparing for a Saturn Radio Science ring occultation experiment coming up on April 11.

ISS performed another observation in the Satellite Orbit Campaign, looking at and for moonlets near Saturn. The Navigation team then took five ISS images of Saturn's moon Dione for optical navigation. Finally, CIRS carried out an eight-hour observation of the rings, mapping temperatures in the planet's shadow to determine the thermal inertia of the ring particles.

Sunday, March 31 (DOY 090)

VIMS observed an occultation of the red star Mu Cephei as it made an egress pass behind the entire ring system from the inner D ring to the outer F ring, all within Saturn's shadow.

CIRS undertook another five hours of ring observations. These included ring particle temperatures within and just exiting Saturn's shadow. Observations in this thermal transition region exert the most leverage in pinning down the particles' thermal inertia.

Monday, April 1 (DOY 091)

The flight team executed an Orbit Trim Maneuver (OTM 346) this morning to refine Cassini's approach trajectory and timing for the Titan T-90 encounter coming up on April 5; the eleven-second RCS-thruster burn provided a 17 mm/s velocity change.

VIMS observed another stellar ring occultation. As seen from the moving spacecraft, the star R Cassiopeia took more than six hours on an ingress pass behind the entire ring system, going from the F ring in to the D ring before disappearing behind Saturn.

ISS made a twelve-hour observation of the Roche Division, which is the gap between the outer A ring and the thin bright F ring. The observation covered one full orbit period at high phase angles, to monitor time-variable azimuthal structures in the ring, including those produced by magnetospheric asymmetries that appear to be tied to the long-wavelength radio emissions from within the planet known as Saturn Kilometric Radiation (SKR).

An image featured today shows the F ring being visited by one of its shepherd moons, as well as some great detail in the outer portion of the A ring: /resources/15766

Tuesday, April 2 (DOY 092)

ISS observed Enceladus's plumes for two hours. This was the second in a widely separated pair of such observations; the first was in December 2012. This "stereo-vision" will add to knowledge of the plumes' three-dimensional structure. Saturn's moon Mimas, which is slightly smaller than Enceladus, was the next target for ISS. A two-hour observation at high-phase illumination looked for any evidence of plumes from this body.

CDA gathered data for six hours while Cassini passed through Saturn's ring plane, to characterize seasonal variation of the E-ring structure. Next, ISS observed the D ring close-up for three hours to monitor time-variable features. This was followed by a high- resolution ISS observation of the F ring, watching ring material pass through the narrow-angle camera's field of view. ISS also captured high-resolution images of the Keeler Gap satellite Daphnis and its associated edge waves (see http://go.usa.gov/2zhW for a previous image). Retargeting known propellers (http://go.usa.gov/YyGR) was ISS's final assignment for today.