News | March 4, 2015
Cassini Significant Events 02/25/2015 - 03/03/2015
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 March 4 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
Milestones spanning the whole orbital tour are listed here: http://saturn.jpl.nasa.gov/mission/saturntourdates . Cassini's position on March 3 is illustrated here: http://saturn.jpl.nasa.gov/mission/saturntourdates .
The view from apoapsis is stunning. This week, Cassini coasted through that slowest, highest, part of its orbital arc, doing some things that are possible only from such a distance ‘’up’’ from Saturn's well of gravitation. Looking back, the cameras showed Saturn's day-night boundary, which is something never to be seen from Earth, and its sunlit rings were visible from edge to edge. As always, images such as these appear right away on the Raw Images page after their data packets have travelled the intervening billion miles and have been converted to images at JPL:
Wednesday, Feb. 25 (DOY 056)
Today's first science activity was a two-minute storm-watch observation of Saturn by the Imaging Science Subsystem (ISS). It finished just before Cassini turned to point its high-gain antenna to Earth for nine hours of communications via the Deep Space Network (DSN). ISS performed another storm watch right afterwards. The Composite Infrared Spectrometer (CIRS) then took control of spacecraft pointing for 10 hours. It performed a low-resolution stare at the sunlit side of Saturn's dense B-Ring to obtain thermal infrared spectra for studying ring-particle composition. The Visible and Infrared Mapping Spectrometer (VIMS) took advantage of this pointing and made observations while riding along. The 10-hour CIRS observation repeated the following day, with ISS joining VIMS as a ride-along instrument.
Thursday, Feb. 26 (DOY 057)
After the CIRS observation, ISS made another 2-minute Saturn storm-watch observation. Late in the day, Cassini reached apoapsis in its orbit about the ringed planet. It had slowed to 5,205 kilometers per hour relative to Saturn, and reached an altitude of 3.5 million kilometers. This marked the start of Cassini's Saturn orbit #213.
Friday, Feb. 27 (DOY 058)
VIMS rode along with a quick ISS storm watch early today. Later, the Cosmic Dust Analyzer (CDA) took the reins for 20 hours to observe dust that orbits Saturn in the retrograde direction. The goal is to characterize particles that have been dislodged from moons like Phoebe, which follows an inclined, retrograde orbit that reaches nearly 13 million kilometers from Saturn. A single measurement of a particle's composition is of inestimable value for characterizing a parent body's surface, linking ring and moon surface properties. CDA began a similar observation on the next day that would last 13.5 hours.
Saturday, Feb. 28 (DOY 059)
As of today, it takes Cassini's radio signals 83 minutes to propagate at light speed across the distance to Earth. Compare this to the 8.3 minutes it takes light from the Sun to get here. As Earth continues eastward in its year-long solar orbit, the communications time to Cassini will continue decreasing by a few seconds every day until May 22, when Saturn reaches opposition in our sky.
Sunday, March 1 (DOY 060)
In between DSN communications sessions over the next three days, the spacecraft remained Earth-pointed for the Magnetospheric and Plasma Science (MAPS) instruments to collect data about the immediate environment.
Monday, March 2 (DOY 061)
An image of Saturn's largest moon's surface is featured today. It was possible to see this clearly through the dense haze thanks to the infrared filter that ISS can rotate into its optical path; a ghostly layer of atmosphere still hangs above. This is one of last January's "Titan monitoring campaign" images that are surely familiar to regular readers of these significant events:
Some of Cassini's scientists met today and the following day, at the SETI (Search for Extraterrestrial Intelligence) Institute at the Ames Research Center in northern California. The topic was Titan and its hydrocarbon-rich, dense atmosphere, and its extraordinary surface.
Tuesday, March 3 (DOY 062)
Cassini's Navigation team resolved one final solution for Cassini's orbital motion based on today's tracking data from the DSN. Flight team members then built commands that will carry out an Orbit Trim Maneuver tomorrow by turning the spacecraft and firing its small rocket thrusters; by day's end the commands were approved for uplink in the morning. This near-apoapsis maneuver will adjust Cassini's flight path for the T-110 Titan encounter on March 16.
During the past week, the DSN communicated with and tracked Cassini on nine occasions, using stations in California and Australia. A total of 100 individual commands were uplinked, and about 1,298 megabytes of telemetry data were downlinked and captured at rates as high as 124,426 bits per second.