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NASA Cassini Significant Events 04/09/08 - 04/15/08

Status Report From: Astronomical Society of Australia
Posted: Tuesday, April 15, 2008

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The most recent spacecraft telemetry was acquired on Tuesday, April 15, from the Goldstone, California tracking complex. 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/operations/present-position.cfm.

Wednesday, April 9 (DOY 100)

Based on analysis performed by members of the Science Planning Team, the live update for Saturn and Tethys due to execute DOY 111-113 has been cancelled. Comparison of the reference trajectory with the maneuver #152 orbit determination solution showed that the Tethys observation had a pointing difference of only 0.53 mrad, not enough to warrant an update.

Announced within the last few weeks both here in the weekly event report and on the Cassini web site, the Cassini Scientist for a Day essay contest has now received international media coverage. NASA Headquarters has added support by sending out an announcement on the Scientist for a Day contest to all of the educators on the NASA Education e-mail distribution list, and proposing an interview about Cassini Scientist for a Day in its "This Week @ NASA" broadcast on NASA TV. In the past week, 24 e-mail requests for additional information have come from students in Canada, Vietnam, Singapore, India, Iran, and Africa, as well as from Americans who are out of the participant age range, but would like to participate anyway.

Thursday, April 10 (DOY 101):

Cassini has two targeted encounters of Enceladus scheduled to occur towards the latter part of this year. E4 is planned for Aug. 11, and E5 on Oct. 9. Today the project held a meeting to determine if the altitudes planned for these flybys should remain as they are in the current trajectory design or if they should be altered. There were pretty strong cases made for leaving E4 as-is, and leaving the E5 altitude as-is but changing the aim point to fly more deeply into the plume. There are a couple of open engineering issues that need to be worked before the final decision is made. These require study by attitude control with atmospheric profiles from the Ion and Neutral Mass Spectrometer (INMS), as well as some follow-up communications with navigation. A wrap-up meeting will be held in the next week or so to discuss the findings and announce the decisions.

Orbit Trim Maneuver (OTM) #152 was performed today. This is the cleanup maneuver following the Titan 42 encounter on March 25. The main engine burn began at 7:15 PM PDT. Telemetry immediately after the maneuver showed the burn duration was 20.16 seconds, giving a delta-V of 3.31 m/sec, as designed. All subsystems reported nominal performance after the maneuver.

Members of the Spacecraft Office Integrated Test Laboratory (ITL) presented a paper at the IEEE Aerospace Conference last month on "System Testbed Use on a Mature Deep Space Mission: Cassini" as well as providing a tour of the ITL facility to members of the Cassini Extended Mission Review Board when they were at JPL.

Friday, April 11 (DOY 102):

A non-targeted flyby of Mimas occurred today.

Today was the first time a Radio Science Receiver (RSR) acquired Cassini Ka-band data over DSS-47, the Narrabri six 22-m antenna array. The proficiency track occurred during a Cassini Radio Science (RSS) rings and ionospheric occultation. Canberra's DSS-34 and Goldstone's DSS-25 were tracking Cassini Ka-band at the same time. The DSS-47 signal power was 2-3 dB higher than observed at the other two 34-m stations. Narrabri's array seemed to track the signal dynamics well throughout the ring occultation period. Although the data still needs to be processed and its quality assessed, especially that of the phase observation which is not monitored in real-time, indications are that once any problems are worked out, Narrabri will have the potential to provide valuable Ka-band support for upcoming Cassini Radio Science observations when needed.

Monday, April 14 (DOY 105):

Seven instrument expanded block (IEB) files in support of the S40 sequence were uplinked by the sequence leads and Mission Support and Services Office personnel today. During the Goldstone pass on DOY-106, an additional six IEBs will be sent with the last file going up on DOY-107. A final sequence approval meeting is scheduled for Tuesday. After that, the background sequence will be uplinked on Wednesday.

Science today began with a continuation of the study of Saturn with a methane fluorescence map taken by the Visual and Infrared Mapping Spectrometer (VIMS) with the Ultraviolet Imaging Spectrograph (UVIS) participating. The next target was Tethys with observations at various wavelengths including Imaging Science (ISS) color photometry, UVIS albedo measurements, and Composite Infrared Spectrometer (CIRS) infrared measurements. As part of the ongoing campaign to better determine the orbits of minor satellites, images were taken of Atlas, Janus, Polydeuces, Prometheus, and Calypso.

Tuesday, April 15 (DOY 106):

NASA Extends Cassini's Grand Tour of Saturn

NASA has approved extending the Cassini-Huygens mission by two years. The mission was originally scheduled to end in July 2008. The newly announced two-year extension will include 60 additional orbits of Saturn, 26 flybys of Titan, seven of Enceladus, and one each of Dione, Rhea and Helene. The extension also includes studies of Saturn's rings, its complex magnetosphere, and the planet itself. Other activities will include monitoring seasons on Titan and Saturn, observing unique ring events such as the 2009 equinox crossing when the sun will pass through the plane of the rings, and exploring new places within Saturn's magnetosphere. Sequence development for the mission extension began last year to enable the S42 sequence to be completed in time for start of execution on July 1, 2008, once approval was received.

The spacecraft will have enough propellant left after the extended mission to potentially allow a third phase of operations. In order to determine if a further mission extension will be feasible, preliminary work on such a mission has begun. The determination of science objectives and opportunities, possible trajectories and supporting analysis take time to develop so the team must begin now to be able to have something - if approved - in place by 2010.

But until then, data from the first mission extension could help lay the groundwork for possible new missions to Titan and Enceladus. For the full release link to: http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=833.

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