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Cassini Significant Events 06/22/11 – 06/28/11

The most recent spacecraft telemetry was acquired on June 28 from the Deep Space Network tracking complex at Canberra, Australia. The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at: http://saturn.jpl.nasa.gov/mission/presentposition/.

Wednesday, June 22 (DOY 173)

A news release called “Cassini Captures Ocean-like Spray at Saturn Moon” is available on the Cassini web site. The Cassini spacecraft has discovered the best evidence yet for a large-scale saltwater reservoir beneath the icy crust of Saturn's moon Enceladus. The data came from the spacecraft's direct analysis of salt-rich ice grains close to the jets ejected from the moon. Data from Cassini's Cosmic Dust Analyzer (CDA) show that the grains expelled from fissures, known as tiger stripes, are relatively small and predominantly low in salt far away from the moon. For more information on this subject link to:

The S69 Instrument Expanded Block (IEB) files were all successfully loaded over the first scheduled DSN track on June 21-22, except for the Ultraviolet Imaging Spectrograph (UVIS) Solid State Recorder (SSR) IEB load which had a dropped terminator packet, causing that load and the subsequent Ion and Neutral Mass Spectrometer (INMS) SSR IEB load not to register and activate. These files were re-radiated over the second uplink window on June 22-23 and were received and executed normally.

Thursday, June 23 (DOY 174)

A Titan Science Meeting concluded today at the Abbaye Saint Jacut-de-la-Mer in Brittany, France. Topics of discussion included the Titan atmosphere, surface, interior, origin, magnetosphere, and plasma environment. This meeting was in part motivated by the production of a Titan science book for Cambridge University Press to appear in 2012.

A kickoff meeting was held today for the S71 Sequence Implementation Process. Port 1 for the first set of input files from the teams occurs July 12.

Friday, June 24 (DOY 175)

Orbit Trim Maneuver (OTM) #287 was performed today. This was the cleanup maneuver following Titan 77 and setting up for the Titan 78 encounter on September 12. The Reaction Control Subsystem (RCS) burn began at 3:00 AM PDT. Telemetry immediately after the maneuver showed a burn duration of 133.6 seconds, giving a delta-V of 0.145 m/s. All subsystems reported normal performance after the maneuver. The next maneuver is scheduled for August 22.

The Science Planning and Sequence Team (SPST) had a tag-up/brainstorming meeting today with the Spacecraft Operations/Attitude and Articulation Control Subsystem (SCO/AACS) team to discuss the status of the Reaction Wheel Assembly Bias Optimization Tool (RBOT) results and what to expect in the first inclined set of orbits (IN-1) coming up. Cassini is currently in the first set of equatorial orbits (EQ-1) - these are good for icy satellite observations, among other things – while inclined revs allow for observations of the polar areas of Saturn and the rings from above and below. The first IN-1 revs begin in S73, and sequence implementation will be starting soon. This meeting provided an informal dialogue with AACS to discuss some of the pointing designs being planned for the IN revs, as well as to get AACS’s opinion on what can be done to try to minimize potential wheel speed constraint impacts. RBOT is a ground software tool that provides the AACS team the capability to optimally select a set of reaction wheel bias spin rates that satisfies the operational constraints placed on the reaction wheels.

Monday, June 27 (DOY 178)

This week in science, a new type of Titan observations began, known as Titan Exploration at Apoapsis, or TEA, observations. The primary objective of these observations is to acquire Imaging Science (ISS) and Visual and Infrared Mapping Spectrometer (VIMS) images at low phase angle in order to detect and monitor the evolution of clouds on Titan. These are continuous observations over periods of up to 37 hours and repeated over the course of one week. An additional goal of the TEA is to detect new molecules and their isotopes in Titan's stratosphere using long integrations with the Composite Infrared Spectrometer (CIRS) instrument. A 7.5 hour TEA on June 22 marked the first observation in this series. Five images were then taken for Optical Navigation, followed by three more TEA observations. The Magnetometer (MAG) performed an 8 hour calibration with the spacecraft rolling about its X-axis. The Cosmic Dust Analyzer (CDA) performed a 29 hour interstellar dust observation, ending this week’s observations.

Tuesday, June 28 (DOY 179)

A set of files was radiated to the spacecraft today over Canberra’s DSS-45 station for uplink of the S69 background sequence, and the AACS End of Sequence (EOS) Reaction Wheel Assembly (RWA) bias and transition to RWA control. S69 has been registered on-board the spacecraft and will start executing on Sunday, July 3.