From: Jet Propulsion Laboratory
Posted: Tuesday, March 18, 2008
The most recent spacecraft telemetry was acquired on Tuesday, March 18, 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" web page located at http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, March 12 (DOY 072):
Traveling at about 15 kilometers per second and at an altitude of 50 km, Cassini flew past Enceladus for its fourth encounter with this moon and its closest flyby to date with any body, and the deepest penetration yet of the Enceladus plumes. The spacecraft passed through the edge of one of the plumes at approximately Enceladus Closest Approach (ECA) + 1 minute. The reaction wheel (RWA) spin rate changes due to the angular momentum imparted on the spacecraft by the plume were -45 rpm, -18 rpm, and -20 rpm, for RWA-1, -2, and -4, respectively.
The science goals for this flyby were: (1) Temperature mapping of the north polar region of Enceladus on approach, to understand surface physical properties and to look for endogenic thermal emission in the northern hemisphere. (2) Detailed mapping of the warm "tiger stripe" fractures at the south pole on departure, in Saturn eclipse, providing the first contiguous regional temperature map with spatial resolution sufficient to resolve the tiger stripes and locate all the major hot spots. (3) Long-wavelength mapping of the south polar region to constrain total heat flow. Much of the heat radiation may be emitted at long wavelengths at which south polar emission was not mapped on the previous Enceladus flybys. (4) Observe the warming of Enceladus as it emerges from Saturn's shadow two hours after the flyby, to understand surface physical properties.
During Cassini's closest approach, two instruments were prime for collecting in-situ plume data--the Cosmic Dust Analyzer (CDA) and the Ion and Neutral Mass Spectrometer (INMS). A software hiccup with CDA prevented it from collecting any data during closest approach, although the instrument did get data before and after the closest approach phase. The other four fields and particles instruments on the spacecraft, in addition to the INMS, captured all of their data, which will complement the overall composition studies and elucidate the unique plume environment of Enceladus.
This was the first of four Cassini flybys of Enceladus this year. If approved, the proposed extended mission will include an additional seven flybys, including the three remaining this year. The next Enceladus flyby will take place in August of this year.
Link here for the official before and after news releases for the Enceladus 3 flyby: http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=822 http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=824
Thursday, March 13 (DOY 073):
The main engine cover, closed during the Enceladus 3 flyby, was opened Mar. 13, before the Orbit Trim Maneuver #149 prime pass. This was 37th cycle - deploy/stow - of the cover since launch.
Orbit Trim Maneuver (OTM) #149 was performed today. This was the Enceladus 3 cleanup maneuver setting up for the Titan 42 encounter on Mar. 25. The main engine burn began at 5:30 PM PDT. Telemetry immediately after the maneuver showed the burn duration was 16.67 seconds, giving a delta-V of 2.76 m/sec, as planned. All subsystems reported nominal performance after the maneuver.
The Cassini/Enceladus E3 blog has been a hit with the public and the media, including several news outlets that linked to the blog. One media outlet said: "The best part
The blog is at: http://blogs.nasa.gov/cm/blog/Enceladus%20Flyby
Friday, March 14 (DOY 074):
The final delivery of Cassini Information Management System (CIMS) inputs for orbits 123-134 occurred today. This is the fourth and final delivery of CIMS inputs prior to sequence integration. Orbits 123-134 are contained within the S55 through S61 sequences at the end of the proposed extended mission.
The Science Operations Plan Update (SOPU) process for S41 completed today. Science Planners are in the process of handing off the package to the sequence leads. S41 is the last sequence in the Cassini Prime Mission.
Monday, March 17 (DOY 077):
A beautiful picture of Enceladus from ~30,000 km away was Astronomy Picture of The Day today, and may be seen at http://antwrp.gsfc.nasa.gov/apod/ap080317.html
A presentation on "The History of Saturn's Rings" was given today in Von Karman auditorium at JPL as part of the Earth and Space Science Colloquium, sponsored by the Office of the Chief Scientist & Chief Technologist and the Science Division at JPL. The following is an the abstract for the presentation: Saturn's rings are made of billions of particles of ice orbiting Saturn. They resemble the planet-forming disks surrounding stars. Cassini observations show Saturn's rings may be ancient, opposite to what has been believed since the first Voyager close up views 25 years ago. Cassini images and occultations give an unprecedented view of ring structure and history. Current ideas suggest that "recycling" can allow the rings to last indefinitely.
Tuesday, March 18 (DOY 078):
Orbit Trim Maneuver (OTM) #150 was performed today. This was the apoapsis maneuver setting up for the Titan 42 encounter on Mar. 25. The reaction control subsystem burn began at 12:44 AM PDT. Telemetry immediately after the maneuver showed the burn duration was 40.5 seconds, giving a delta- V of 0.055 m/s. All subsystems reported nominal performance after the maneuver.
JPL's Office of Communications and Education is proud to present the 2008 Theodore von Kármán Lecture Series.
"Enceladus: The Newest Wrinkle from Saturn's Tiger-Striped Moon" Thursday, March 20th, in the Theodore von Kármán Auditorium at JPL, and Friday, March 21st, at Pasadena City College's Vosloh Forum, 1570 East Colorado Boulevard. Both lectures begin promptly at 7 PM, with seating available on a first come, first served basis. For more information about the event call the Public Services Office at 818 354-0112, or visit their web site at http://www.jpl.nasa.gov/pso/lectures.cfm
Check out the Cassini web site at http://saturn.jpl.nasa.gov for the latest press releases and images.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.
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