NASA Cassini Significant Events for 08/20/2014 – 08/26/2014

Cassini is orbiting Saturn with a 31.9-day period in a plane inclined 44.6 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on Aug. 26 using one of the 34 meter-diameter Deep Space Network (DSN) stations at Canberra, Australia. The spacecraft continues to be in an excellent state of health with all of its subsystems operating normally except for the instrument issues described at http://saturn.jpl.nasa.gov/news/significantevents/anomalies. Information on the present position of the Cassini spacecraft may be found on "Eyes on the Solar System":

http://1.usa.gov/1pEI4aQ

This week's highlight was the T-104 encounter with Saturn's enigmatic moon Titan early Thursday morning. During the close encounter, all the spacecraft's rotations and scientific observations executed with precision, commanded by the on-board S85 command sequence. The DSN captured every bit of the long-distance telemetry playback on the following day. Thanks to the DSN's exquisitely sensitive radiometric tracking, the Cassini Navigation team determined that the spacecraft had flown within 90 meters of its target. With such accurate targeting, Monday morning's opportunity to execute a post-encounter trajectory-cleanup rocket firing did not have to be used.

Wednesday, Aug. 20 (DOY 232)

Dutifully following Newton's and Kepler's laws, Cassini began slowing a bit while coasting up and away from yesterday's Saturn-orbit periapsis. Today the spacecraft rotated so that its telescopic instruments could begin their observations of Titan across the spectrum. From now until Friday, Titan came under the close scrutiny of the Visible and Infrared Mapping Spectrometer (VIMS), the Imaging Science Subsystem (ISS), the Composite Infrared Spectrometer (CIRS), and the Ultraviolet Imaging Spectrograph (UVIS). At times, more than one instrument "rode along," acquiring data while another instrument had command of the ship's attitude.

In addition to the remote-sensing instruments' observations, Cassini's direct-sensing instruments made essentially continuous observations during this segment as well: the Magnetometer, the Magnetospheric Imaging Instrument, the Radio and Plasma Wave Science instrument, and the Ion and Neutral Mass Spectrometer (INMS).

Inbound to Titan today, CIRS focused on mid- and far-infrared nadir integrations to measure the abundances of carbon monoxide, water, and cyanide. ISS made a mosaic of southern latitudes on Titan's sub-Saturnian hemisphere, and VIMS took low resolution images while riding along with ISS. Observations covered latitudes between the equator and 60 degrees south, and included monitoring the south polar vortex.

Thursday, Aug. 21 (DOY 233)

RADAR operated in altimetry mode, and later made high-priority SAR-mode observations. INMS served as the spacecraft's primary instrument inbound near closest approach, commanding the best spacecraft attitude for ingesting and analyzing the content of Titan's ionosphere. Subsequently, INMS rode along while RADAR controlled pointing.

On the outbound leg after RADAR finished, VIMS became prime. It monitored the northern great lake Kraken Mare at the point where a specular reflection of infrared sunlight might be glimpsed. Catching one would help assess whether liquids are still present, and if still liquid whether winds create waves on the surface. VIMS also looked for clouds at high northern latitudes and mapped the north polar area to monitor the evolution of its lakes and seas. ISS acquired a mosaic of northern latitudes on Titan's trailing hemisphere.

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NASA Cassini Significant Events for 08/20/2014 - 08/26/2014

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