News | February 4, 2015
Cassini Significant Events 01/28/2015 - 02/03/2015
Cassini is currently orbiting Saturn with a 31.9-day period in a plane inclined 19.1 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on Feb. 3 using the 70-meter diameter Deep Space Network station 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
The S87 command sequence, which is stored in the spacecraft's memory, controlled most of Cassini's activities this week. Meanwhile, members of the Sequence Implementation Process teams, led from JPL with members in the US, Germany, Italy, and the UK continued working to develop the 10-week command sequences S88, S89, and S90. Planning work continued for the mission's activities in 2016 including the start of the F-ring orbits, and the 2017 Grand Finale.
Wednesday, Jan. 28 (DOY 028)
The Cosmic Dust Analyzer (CDA) performed two back-to-back, nine-hour observations today as part of the exogenous dust campaign, measuring dust that comes in from outside of the Saturn system. A third one followed on the next day.
When Cassini passed close by Saturn's largest moon Titan in December 2013, it was a unique encounter. Never before, and never again, would Cassini have the chance to study the giant moon and its ionosphere while it was awash in the supersonic solar wind, outside of Saturn's protective magnetic field. Results from this encounter were published today in the journal "Geophysical Research Letters" and are condensed here:
Thursday, Jan. 29 (DOY 029)
Saturn rises before dawn these days, and can be found in the eastern sky not far above the red-giant star Antares; it looks off-white to the unaided eye, and doesn't twinkle the way stars seem to do. The radio signal from Cassini in orbit there took 86 minutes to propagate to Earth today, where it was received by the 70-meter diameter Deep Space Network station in Australia. It takes the same amount of time for its reflected sunlight to reach Earth, of course, and anyone with at least a small telescope can see the gas giant's slightly flattened globe, and at least two or three of its main rings, and orange-hued Titan. The planet's shadow is clearly visible behind it on the rings.
Friday, Jan. 230 (DOY 030)
The Ultraviolet Imaging Spectrograph (UVIS) controlled Cassini's pointing to track and observe Saturn’s northern aurora for 13.3 hours today, with the Composite Infrared Spectrometer (CIRS), and the Visible and Infrared Mapping Spectrometer (VIMS) riding along. The remote-sensing observation, together with data from the direct-sensing Magnetospheric Imaging Instrument (MIMI) and the Magnetometer (MAG), investigated how the aurora's morphology and intensity responds to different solar wind conditions. Similar observations were repeated on the next day for 15 hours, and again on Monday for seven hours.
Saturday, Jan. 31 (DOY 031)
While still out near apoapsis in its Saturn orbit, Cassini took advantage of the orbital-mechanics "leverage" and carried out a propulsive maneuver today. Based on commands uplinked in real time, the spacecraft turned and fired its bipropellent-fed main engine for seven seconds. This Orbit Trim Maneuver (OTM)-402 provided a change in Cassini's velocity of 1.3 meters per second, targeting the spacecraft for a 1200-kilometer altitude flyby of Titan, the T-109 encounter, on Feb. 12.
Sunday, Feb. 1 (DOY 032)
Following another one of its communications sessions with the Deep Space Network today, the spacecraft remained in an Earth-pointed attitude while the Magnetospheric and Plasma Science (MAPS) instruments collected data.
Monday, Feb. 2 (DOY 033)
UVIS began a 31-hour observation of Saturn’s northern aurora; CIRS and VIMS rode along.
Of the three small satellites that orbit Saturn just beyond the narrow F ring, Epimetheus is larger than Pandora, and smaller than Janus (featured two weeks ago), which shares its orbit. With the image of Epimetheus featured today is an interesting comparison with the mass of the rings:
A view of infrared sunlight glancing off Titan's surface, as observed by VIMS, was selected as NASA's Astronomy Picture of the Day today:
Tuesday, Feb. 3 (DOY 034)
After UVIS completed the auroral observation it started on the previous day, ISS took command of the spacecraft's attitude so it could track and observe Saturn's irregular moon Siarnaq for 8.25 hours. Siarnaq is the largest of the five objects in the Inuit group, which have distant, eccentric, inclined orbits about the planet.
During the past week, the Deep Space Network communicated with and tracked Cassini on six occasions, using stations in Australia and California. A total of 151 individual commands were uplinked, and about 1,279 megabytes of telemetry data were downlinked and captured at rates as high as 124,426 bits per second.