Cassini Significant Events 01/25/2012 – 01/31/2012

The most recent spacecraft tracking and telemetry data in this reporting period were acquired on Feb. 1 from the Deep Space Network 34 meter Station 26 at Goldstone, California. The Cassini spacecraft is in an excellent state of health with all subsystems operating normally except for the known issues with the Cassini Plasma Spectrometer and the Ultrastable Oscillator. Information on the present position and speed of the Cassini spacecraft may be found on the “Present Position” page at:

This week, command sequence S72 started its science observations with a Titan Meteorological Campaign, in which the Imaging Science Subsystem (ISS) looked for cloud events. The Ultraviolet Imaging Spectrograph (UVIS) then executed slow scans in the extreme- and far-ultraviolet across Saturn’s illuminated hemisphere. The Visual and Infrared Mapping Spectrometer (VIMS) concentrated on the remains of the storm in Saturn’s northern hemisphere, which has been raging since December 2010. Scientists think the String of Pearls ( may be hidden beneath the storm, and after the storm wanes will try to discover whether the feature may have been destroyed by the tempest. ISS then acquired images over a range of latitudes at low, medium, and high emission angles as the planet rotated. (Emission angle is the angle between the camera boresight and a line normal to the surface point being imaged; straight down is zero degrees.)

The Composite Infrared Spectrometer (CIRS) mapped Saturn’s prime meridian from the north pole to the equator to determine the upper troposphere and tropopause temperatures with spatial resolutions of about two degrees of latitude and longitude. Following this, VIMS acquired a high spatial resolution map of the dynamics of Saturn’s deep atmosphere. VIMS imaged the same area twice, measuring winds via motions of the clouds. Since these observations were made while the spacecraft was near periapsis, clouds as small as 300 kilometers wide were detectable.

RADAR mapped the same deep region at and around periapsis, obtaining radiometry data at microwave wavelengths much longer than those seen by VIMS. These RADAR maps looked for ammonia gas to reveal the variability of this condensable constituent over the same area where VIMS mapped clouds (formed either via chemical reaction with hydrogen sulfide, thus forming ammonia hydrosulfide clouds, or via direct condensation into ammonia clouds). Unfortunately, this carefully collected RADAR data set and most of the corresponding VIMS data were lost when heavy Australian summer rainstorms drowned out Cassini’s signal while it was arriving at Earth on Sunday, January 29.

Targeted Titan encounter T-81 then executed perfectly on January 30, as detailed below.

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