Cassini Significant Events 02/11/2015 – 02/17/2015

Cassini is currently orbiting Saturn with a 31.9-day period in a plane inclined 8.5 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on Feb. 17 using one of the 34-meter diameter Deep Space Network stations in 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 . Milestones spanning the whole orbital tour are listed here: http://saturn.jpl.nasa.gov/mission/saturntourdates .

Cassini spent this week arcing away from periapsis in its Saturn orbit, which it passed last Tuesday morning. It then made a rendezvous with Saturn's 5,152-kilometer diameter moon Titan on Thursday, flying 1,200 kilometers above its extraordinary surface. In addition to science investigations, Cassini uses each Titan encounter to shape the spacecraft's next orbit of Saturn, almost always returning to Titan the very next time around. The gravity assist from this week's encounter further decreased Cassini's orbital inclination, bringing it down from 19.1 degrees to 8.5 degrees. The next Titan gravity assist, on March 16, will put Cassini within a fraction of a degree of Saturn's ring plane again. The most recent orbits that Cassini flew in Saturn's equatorial plane were in May of 2012.

Wednesday, Feb. 11 (DOY 042)

Having swung around to the night side of Saturn, Cassini turned to point the Composite Infrared Spectrometer (CIRS) at one location on the planet for nearly ten hours to derive the atmosphere's chemical composition. The Ultraviolet Imaging Spectrograph (UVIS) and the Visible and Infrared Mapping Spectrometer (VIMS) rode along. Next, the Imaging Science Subsystem (ISS) made a close-in examination of Saturn's D ring, the innermost ring near the planet. CIRS and VIMS rode along taking data on this high-priority observation.

A news feature released today illustrates a new technique for processing Cassini's synthetic-aperture radar data to produce cleaner image results:
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20150211 .

Thursday, Feb. 12 (DOY 043)

At the start of the day, Titan loomed a little closer to Cassini than Earth's Moon is to Earth. By late in the day, Cassini made its closest approach near Titan's terminator, by the north pole. While the optical remote-sensing instruments were busy examining Titan's surface, the direct-sensing Magnetospheric and Plasma Science instruments studied the draping and diffusion of Saturn's external magnetic field within Titan's ionosphere over the flank facing Saturn. The T-109 flyby page has more detail:
http://saturn.jpl.nasa.gov/mission/flybys/titan20150212 .

Friday, Feb. 13 (DOY 044)

With Titan quickly receding, CIRS led a four-hour observation to map its northern latitudes in the far-infrared part of the spectrum, measuring the vertical distributions of gas and aerosols; ISS, UVIS, and VIMS observed in ride-along mode. Next, CIRS spent 8.25 hours making a thermal map of Titan in the mid-infrared with ISS and VIMS riding along.

During communications sessions using Deep Space Network (DSN) stations in Australia today and the following day, the flight team uplinked commands called Instrument-Expanded Blocks. These will support execution of the next ten-week command sequence, S88, when it takes control on Feb. 21. In all, there were 11,787 individual commands, all of which were received and confirmed by telemetry as properly stored on board.

Saturday, Feb. 14 (DOY 045)

Near the end of the day, CIRS turned back to Saturn to observe the atmosphere for 13 hours in order to better understand its composition.

Today marks 25 years since either of the two Voyager Spacecraft last took an image of Saturn. At that time, Voyager 1 also captured the rest of the solar system in one mosaic, before shutting off its imaging system for good. The renowned Solar System Portrait also shows Earth as a pale blue dot. (Both Voyagers still operate their fields and particles instruments and maintain routine communications via the DSN.) The portrait was today's Astronomy Picture of the Day: http://apod.nasa.gov/apod/ap150214.html .

Sunday, Feb. 15 (DOY 046)

Shortly after Cassini turned to face its high-gain antenna dish to Earth, it found commands arriving that would perform Orbit Trim Maneuver (OTM)-404. Cassini turned and fired its bi-propellant-fed main rocket engine for three seconds. This provided a change in velocity of 0.5 meters per second to clean up errors in the spacecraft's trajectory following the T-109 flyby.

Monday, Feb. 16 (DOY 047)

ISS controlled the spacecraft's pointing to observe Saturn's faint rings, back-lit by the Sun, for 15 hours; VIMS rode along. The images will be used to make a movie.

Another view of Saturn's small moon Janus is the featured image today: {"ISEXTERNALURL":"0"}

Tuesday, Feb. 17 (DOY 048)

During the past week, the Deep Space Network communicated with and tracked Cassini on eight occasions, using stations in Australia and Spain. A total of 11,938 individual commands were uplinked, and about 2,186 megabytes of telemetry data were downlinked and captured at rates as high as 124,426 bits per second.