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Cassini Significant Events 10/19/11 – 10/25/11

The most recent spacecraft telemetry was acquired on October 25 from the Deep Space Network tracking complex at Madrid, Spain. The Cassini spacecraft is in an excellent state of health and with the exception of the CAPS instrument being powered off, 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, Oct. 19 (DOY 292)

Today Cassini flew by Enceladus at an altitude of 1,231 kilometers and a speed of 7.4 km/sec. This flyby featured a dual stellar occultation in which the ultraviolet spectrograph observed two of the three stars that make up Orion's belt as they passed behind the moon's plumes. Scientists hope to better understand the density, composition, and variability of the jets from these observations. Infrared instruments and cameras also monitored activity on the moon. For more information and raw images, link to: http://saturn.jpl.nasa.gov/mission/flybys/enceladus20111019/.

Today the Instrument Operations System/Multi Mission Image Processing Laboratory (IO/MIPL) group expedited processing for the Enceladus 15 flyby, delivering images to the science team and raw image website during the downlink.

The main engine cover was closed on Monday, Oct. 17, for dust hazard avoidance, and was reopened today. This was the 67th in-flight cycle of the cover.

A non-targeted flyby of Telesto occurred today.

Thursday, Oct. 20 (DOY 293)

The Navigation Team found that the latest orbit solution had the spacecraft close enough to the reference trajectory after the E-15 flyby on Oct. 19 that execution of Orbit Trim Maneuver (OTM) #296, the E-15 cleanup maneuver, was not needed. OTM-296 was therefore canceled.

The next maneuver, OTM-297, targeting the 500 kilometer altitude Enceladus 16 flyby on November 6, is scheduled to execute on Oct. 28, and then is followed by OTM-298 and OTM-299, the E-16 approach and cleanup maneuvers, scheduled to execute Nov. 2 and Nov. 8 respectively. There's a possibility of canceling OTM-297 as well if the planned science observations can tolerate an ~70 kilometer miss at E-16. The Navigation team will give the science teams the current trajectory estimate to decide if it's close enough for their observations.

A number of Cassini scientists attended the Outer Planets Assessment Group (OPAG) meeting Oct. 19-20 in Pasadena, CA. This is a NASA-supported forum for scientists and engineers to discuss exploration of the outer solar system and to enhance communication between the science community and NASA. Additional links to the agenda and presentations are available on the OPAG website at: http://www.lpi.usra.edu/opag/.

Monday, Oct. 24 (DOY 297)

A week-long series of presentations and discussions begins today at the 55th meeting of the Cassini Project Science Group (PSG) held at JPL. The meeting objective and key theme is the Senior Review preparation and team budget discussions, and to review the status of the Solstice Mission activities.

Tuesday, Oct. 25 (DOY 298)

Science activities on the spacecraft this week began with Enceladus E-15 flyby observations as the suite of optical instruments observed the surface of the moon as well as its dramatic plume and jets. Half an hour before closest approach, the Ultraviolet Imaging Spectrograph (UVIS) took control of the spacecraft to observe two stars in Orion’s Belt, epsilon Ori and zeta Ori, as they passed behind the plume of Enceladus. This observation gave a measurement of the vertical structure in the plume, and will help in pinning down collimation of gas in the jets. Once the occultation was completed, the Composite Infrared Spectrometer (CIRS) observed the surface of Enceladus as the spacecraft receded from the moon. Observations continued when Enceladus was in eclipse, i.e., in Saturn’s shadow, which provided a good opportunity for CIRS to investigate how different parts of Enceladus cool down during the eclipse and warm up again once sunlight returns.

After the Enceladus flyby, Imaging Science (ISS), CIRS, and the Visual and Infrared Mapping Spectrometer (VIMS) observed the G ring arc at low elevation and low phase angle for 10 hours, and UVIS performed a three hour calibration using the star Spica. ISS, CIRS and VIMS then performed a Titan monitoring observation, and ISS performed another couple of observations in its Satellite Orbit Campaign, making astrometric measurements of some of Saturn's small inner moons. ISS made a 15-hour observation of the lightcurve of the outer irregular moon, Loge, and CIRS later created a 23 hour mid-infrared map of Saturn to determine upper troposphere and tropopause temperatures.

Cassini lastly began a new phase of Titan observations known as Titan Exploration at Apoapsis, or TEA, whose primary objective is to acquire ISS and VIMS images at low phase angle in order to detect and monitor the evolution of clouds on Titan, and to detect new molecules and their isotopes in Titan's stratosphere using long integrations with the CIRS instrument. TEAs are continuous observations over periods of up to 37 hours and repeated over the course of one week. This series of TEAs was primarily dedicated to atmospheric composition and began with a 19 hour and a 13 hour observation by CIRS and ISS, ending this week’s observations.

The S71 Final Sequence Integration and Validation (FSIV) Sequence Change Request (SCR) approval meeting was held today. There is ongoing work to get the latest DSN station allocations in as soon as possible to minimize real time commanding for any DSN changes coming in after the SCR approval date.