From: Jet Propulsion Laboratory
Posted: Monday, December 16, 2013
Cassini is orbiting Saturn with a 31.9-day period in a plane inclined 51.3 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on Dec. 11 using the 70-meter diameter Deep Space Network station at Canberra, Australia. Except for the science instrument issues described in previous reports (for more information search the Cassini website for CAPS and USO), the spacecraft continues to be in an excellent state of health with all of its subsystems operating normally. Information on the present position of the Cassini spacecraft may be found on "Eyes on the Solar System" at
The S81 command sequence, which is stored in the spacecraft's memory, controlled all 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 ten-week command sequences S82, S83, and S84. Planning also proceeded for the 2016 start of Cassini's F-ring and Proximal Orbits phase.
Wednesday, Dec. 4 (DOY 338)
The Imaging Science Subsystem (ISS) performed an observation in the satellite orbit campaign, looking near Saturn for small objects. The Visible and Infrared Mapping Spectrometer (VIMS) then created an 11-hour movie of Saturn's south polar region to study atmospheric dynamics. The Composite Infrared Spectrometer (CIRS) rode along to take data, and then started an observation of Saturn's rings in the planet's shadow to map ring temperatures and help determine the particles' thermal inertia.
Orbit Trim Maneuver (OTM) 365 had been planned to clean up the trajectory today, following Sunday's Titan T-96 encounter, but the Cassini Navigation team found, based on radiometric tracking, that the encounter was accurate enough, and the OTM would not be needed. The maneuver was cancelled.
Saturn's complete north polar region is normally out of view from Earth, but Cassini's extensive views from highly inclined orbits have enabled stunning results. Today's news release presents short high-resolution movies, in the visible and in the infrared, of the swirling atmospheric phenomena there including the persistent hexagonal jet stream that is unique in our solar system:
Thursday, Dec. 5 (DOY 339)
CIRS completed its observation of the shaded rings. Next, with ISS and VIMS riding along it observed Saturns southern hemisphere for twelve hours in an effort to determine upper troposphere and tropopause temperatures.
Friday, Dec. 6 (DOY 340)
ISS created a 15-hour movie of the F ring at low resolution, with CIRS and VIMS also taking data. The movie's duration was long enough to capture one full revolution of F-ring particles about Saturn.
NASA's interactive simulation system, "Eyes On the Solar System," now has a special module featuring the Cassini Mission. Use "Eyes" to fly along with any spacecraft, or see accurate perspectives on just about any solar system object from just about any perspective:
Saturday, Dec. 7 (DOY 341)
ISS created a nine-hour medium-resolution movie of the D ring at high phase, a lighting condition that best illuminates its fine particles. CIRS rode along. (Note that Cassini plans to fly interior to this ring in 2017.)
Sunday, Dec. 8 (DOY 342)
The Magnetospheric and Plasma Science (MAPS) instruments began an eight-day campaign today to study Saturn's magnetotail.
On five occasions this week Cassini turned to train its high-gain antenna on Earth so the Deep Space Network could carry out digital communications and radiometric tracking, using its 34-meter and 70-meter diameter stations. The DSN systems captured telemetry from Cassini's X-band (8 GHz) downlink at up to 110,601 bits per second, while transmitting an X-band uplink to Cassini at the same time. Cassini received routine commands, and also used the uplink as its frequency reference to provide the highly accurate radiometric tracking needed for navigation, via the radio signal's Doppler shift and distance-measuring Ranging signals.
Monday, Dec. 9 (DOY 343)
In an image featured today, the 136 kilometer-long, oblong moon Prometheus can be seen near the inside of Saturn's F ring. Looking closely reveals how the little moon's gravity affects the dusty F-ring material. Prometheus orbits Saturn once every 14.64 hours, while the F ring particles take a little longer, about 14.88 hours, to complete their orbits. Prometheus's orbit is slightly less circular than that of the rings. On the right, towards the planet, the thin Keeler Gap in the A ring shows some irregular waves or wakes along its edges.
Tuesday, Dec. 10 (DOY 344)
Two of Cassini's many stunning findings were featured this week in Time Magazine's "Science and Space" online column: Saturn's North Pole Hurricane, which is mentioned above, and The Great Lakes on Titan:
Visit the JPL Cassini home page for more information about the Cassini Project:
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