News | March 25, 2015
Cassini Significant Events 03/18/2015 - 03/24/2015
Cassini is currently orbiting Saturn with a 28-day period in a plane inclined 0.3 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on March 24 using the newest 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 .
Cassini spent this week tracing along an orbit outbound from Saturn that is now basically equatorial -- very near the plane of the rings and icy satellites. It will remain so for the remainder of 2015, during which time the spacecraft will make repeated close encounters not only with the usual target of 5,152-kilometer diameter Titan, (four times), but also with the 1,122-kilometer diameter Dione (twice), and the 504-kilometer geyser-moon Enceladus (three times).
Wednesday, March 18 (DOY 077)
Today's nine-hour Deep Space Network (DSN) tracking and communications period was fairly typical. As soon as the Australian DSN station finished orienting its 34-meter diameter Cassegrain reflector towards Saturn, Cassini's signal began arriving, right on time. Today was a little different, though, because along with the X-band (8 GHz) signal carrying the usual phase-symbols for digital telemetry data, there was, as planned, a Ka-band (32 GHz) signal -- a pure tone without telemetry -- that the Radio Science Team used for performing a calibration exercise at the station.
After the end of the DSN pass, the Composite Infrared Spectrometer (CIRS) directed spacecraft pointing for 15 hours to observe Saturn's atmosphere in the far-infrared part of the spectrum, in an effort to determine temperatures in the upper troposphere and tropopause. The Visible and Infrared Mapping Spectrometer (VIMS) took advantage of the pointing and rode along making its own observations.
Thursday, March 19 (DOY 078)
Today, the 10-week long S88 sequence of commands in Cassini's memory reached a planned period of inactivity reserved for the flight team at JPL to command an Orbit Trim Maneuver near real time. However the Navigation team, having measured the accuracy of last Monday's T-110 Titan flyby, determined that this trajectory cleanup maneuver would not be needed. OTM-407 was therefore cancelled.
Friday, March 20 (DOY 079)
Following another DSN pass, the spacecraft remained in an attitude with its high-gain antenna pointed to Earth for most of the day, while the direct-sensing Magnetospheric and Plasma Science (MAPS) instruments collected data about Cassini's environment. Later, VIMS, CIRS and the Ultraviolet Imaging Spectrograph (UVIS) began a 31-hour long observation of the faint, outer G and E rings while they were illuminated at high phase-angle -- back-lit by sunlight, so that forward scattering would make their fine particles show up more brightly.
Saturday, March 21 (DOY 080)
An image featured this week shows a beautiful sector of Saturn's complex outer A ring and knotty F ring, along with three small satellites. Pan speeds around its 838,000-kilometer racetrack about Saturn once every 13.9 hours, while Pandora spends 15.1 hours moving along its more distant circuit. The image is here:
Sunday, March 22 (DOY 081)
With the observation of Saturn's G ring and E ring complete, the Imaging Science Subsystem (ISS) undertook a study of the faint rings at low elevation angles and high-phase illumination that would take 20 hours to complete. Both CIRS and VIMS rode along for this activity.
Monday, March 23 (DOY 082)
The Cosmic Dust Analyzer (CDA) took control of the spacecraft's attitude to start a 24-hour long sampling of dust that orbits Saturn in the retrograde direction.
Tuesday, March 24 (DOY 083)
When CDA completed its retrograde dust observation, ISS turned to look at Saturn for a two-minute storm watch. Finally, CIRS took over to stare at Saturn for 21 hours, obtaining spectra to better understand the atmosphere's chemical composition. ISS and VIMS participated with ride-along observations.
During the past week, the DSN communicated with and tracked Cassini on six occasions, using stations in California and Australia. A total of 11 individual commands were uplinked, and about 897 megabytes of telemetry data were downlinked and captured at rates as high as 142,201 bits per second.
This illustration shows Cassini's position on March 24: https://space.jpl.nasa.gov/cgi-bin/wspace?tbody=-82&vbody=1001&month=3&day=24&year=2015&hour=23&minute=55&fovmul=1&rfov=40&bfov=30&brite=1&showsc=1&showac=1 .
Milestones spanning the whole orbital tour are listed here: http://saturn.jpl.nasa.gov/mission/saturntourdates .
Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at: