Cassini Significant Events<br />for 06/10/04 - 06/16/04<br /> <br />The most recent spacecraft telemetry was acquired from the Goldstone<br />tracking station on Wednesday, June 16th. The Cassini spacecraft is in an<br />excellent state of health and is operating normally. Information on the<br />present position and speed of the Cassini spacecraft may be found on the<br />"Present Position" web page located at<br />
http://saturn.jpl.nasa.gov/operations/present-position.cfm .<br /> <br />On Friday, June 11th, 2004, Cassini made its first encounter with a member<br />of the Saturn system. This week's Phoebe encounter, the only flyby of an<br />outer Saturnian satellite in the mission, and the first close flyby ever of<br />an irregular Saturnian satellite, was spectacularly successful! Cassini came<br />within approximately 2,068 kilometers of the dark moon. It has been 23 years<br />since the Voyager 2 flyby of Phoebe in 1981 at 2.2 million kilometers, more<br />than 1,000 times farther away.<br /> <br />Since all of the optical remote sensing instruments were pointing towards<br />Phoebe during the flyby, it was not until several hours later that the<br />spacecraft turned to relay the data back to Earth. The signal was received<br />on Saturday, June 12th, through the Deep Space Network antennas in Madrid,<br />Spain and Goldstone, California. Five instruments reported taking<br />significant data: the Composite Infrared Spectrometer (CIRS), Imaging<br />Science Subsystem (ISS), RADAR, Ultraviolet Imaging Spectrograph (UVIS), and<br />the Visible and Infrared Mapping Spectrometer (VIMS).<br /> <br />These instruments returned a wealth of scientific data on this tortured and<br />battered moon, thanks to the success of the Live Update process that enabled<br />a last minute modification in the pointing of the spacecraft to more<br />accurately target Phoebe. Further analysis of the data over the next<br />several weeks will begin to unravel the moon's past and possible age and<br />origin, resolve its mass and physical properties, and begin to shed light on<br />the moon's composition, surface properties, and topography.<br /> <br />VIMS will provide the first ever resolved spectra of the surface of Phoebe,<br />up to 0.5 km/pixel at closest approach, with full range 0.4 to 5-micron<br />spectra. This data will be used to derive compositional maps of Phoebe's<br />surface.<br /> <br />Phoebe is an exceptionally interesting target for CIRS, due to its unusual<br />surface composition compared to most of the icy satellites and its<br />relatively warm temperatures, which will provide high signal to noise data.<br />CIRS performed compositional and thermal observations to assist in<br />identifying Phoebe's origins and surface properties including global mapping<br />of composition and both day and night temperature distributions.<br /> <br />UVIS measured Phoebe's ultraviolet surface reflectance, providing the first<br />ultraviolet albedo map of this interesting body. The UVIS measurements will<br />aid in understanding Phoebe's compositional makeup and distribution of<br />volatiles.<br /> <br />RADAR team members were excited, as it has been a long time between<br />observations. The last opportunity was 5 years ago at the time of the Earth<br />flyby in June of 1999. RADAR observations of Phoebe penetrated to between 2<br />cm and 20 cm, and will constrain the bulk density and/or the relative ice<br />cleanliness in the upper layer of regolith. This along with volume derived<br />from imaging data will help determine if it is a highly porous 'rubble pile'<br />based on its low density, or a more compact body as might be suggested from<br />its roughly spherical shape. The density value will also be used to<br />constrain its composition and indicate the rough proportions of rock and ice<br />in its make-up.<br /> <br />ISS will contribute multi-color mapping of almost the entire surface at 0.3<br />to 2.1 kilometers per pixel resolution. The first high-resolution images of<br />Phoebe show a scarred surface, covered with craters of all sizes and large<br />variations of brightness across the surface, giving strong evidence that the<br />tiny moon may be rich in ice and covered by a thin layer of darker material.<br />Phoebe is a world of dramatic landforms, with landslides and linear<br />structures such as grooves, ridges and chains of pits.<br /> <br />Although working groups must convene to discuss and refine conclusions, the<br />Cassini science community and flight team are extremely pleased and<br />excitement is running high. This attitude is reflected in the response of<br />the general public to this event.<br /> <br />On June 14, a Cassini picture of Phoebe was Astronomy Picture of the Day.<br />Also last week the flyby achieved the top science story spot on the Google<br />website.<br /> <br />JPL has released multiple press releases and images, and CNN.com, NASA Ames<br />Research Center, and ESA published additional articles. Go to<br />
http://saturn.jpl.nasa.gov to access these items. Links to other sites<br />referenced in this status report are listed below.<br /> <br />Astronomy Picture of the Day<br />If "today" for you is no longer June 14, 2004, then go to:<br />
http://antwrp.gsfc.nasa.gov/apod/ap040614.html<br /> <br />Google<br />
http://news.google.com/news/en/us/technology.html<br /> <br />CNN.com - Space probe fly-by of Saturn's moon - Jun 11, 2004<br />
http://www.cnn.com/2004/TECH/space/06/11/saturn.moon/index.html<br /> <br />NASA SCIENTIST HOPES TO EXPLAIN SATURN'S MYSTERIOUS 'BLACK' MOON<br />June 9, 2004<br />
http://www.arc.nasa.gov/aboutames-pressrelease-print.cfm?id=15000128<br /> <br />Cassini-Huygens looks at Phoebe's distant past<br />European Space Agency<br />14 June 2004<br />
http://www.esa.int/esaCP/SEMNL63VQUD_index_0.html<br /> <br />Additional spacecraft activities this week included the successful execution<br />of Trajectory Correction Maneuver (TCM) -21. The "quick look" immediately<br />after the maneuver showed the burn duration was 38.38 sec, giving a change<br />in velocity of 3.68 meters/second.<br /> <br />The SOI critical sequence was also successfully uplinked to the Command and<br />Data Subsystem's main memory. The critical sequence is on board and waiting<br />for the "activate" command which will be radiated this coming Thursday, June<br />17, 2004. Additional on-board instrument activities included a Radio and<br />Plasma Wave Science instrument Periodic Instrument Maintenance.<br /> <br />In the last week, 994 ISS images were obtained and were distributed along<br />with 1160 VIMS cubes. The total number of ISS images acquired since the<br />start of Approach Science is now 11976, and the number of VIMS cubes is<br />4085.<br /> <br />Sequence development activities are proceeding on schedule. The official<br />port #2 for Science Operations Plan (SOP) Implementation of tour sequences<br />S29 and S30 occurred this week, as well as the official port #1 for tour<br />sequences S31 and S32. All products have been merged and handed to the ACS<br />team for the end-to-end pointing validation.<br /> <br />Preliminary port #1 for SOP Update for tour sequence S04 occurred this week.<br />The products were merged and reports delivered to the instrument team. As<br />part of the Aftermarket process for S06, an assessment meeting was held.<br />Since changes to the sequence were minimal, they were determined to fit<br />within the available resources.<br /> <br />The S02 background sequence and Probe Checkout #14 sequence were approved at<br />the S02 Sequence Approval meeting. Both files will be uplinked to the<br />spacecraft next week. S02 begins execution on Saturday June 19. The Probe<br />Checkout activity is designed to simulate to release of the probe from the<br />orbiter.<br /> <br />In support of SOI activities, a Playback Assessment Meeting has been<br />scheduled for July 2. The purpose of this meeting is for the instruments to<br />report whether or not they found the SOI playback to be sufficient, based on<br />pre-determined criteria. This is part of the contingency plan to ensure<br />success of the overall orbit insertion activity.<br /> <br />Outreach activities include the formal release of the "Reading, Writing, and<br />Rings" lesson set for grades 3 and 4. This release marks the culmination of<br />development on Cassini's blended language arts and science lesson sets for<br />elementary school classrooms. All materials are now available to download<br />from the education section of the Cassini website.<br /> <br />Cassini is a cooperative project of NASA, the European Space Agency and the<br />Italian Space Agency. The Jet Propulsion Laboratory, a division of the<br />California Institute of Technology in Pasadena, Calif., manages the Cassini<br />mission for NASA's Office of Space Science, Washington, D.C.<br /> <br />Cassini Outreach<br />Cassini Mission to Saturn and Titan<br />Jet Propulsion Laboratory<br />California Institute of Technology<br />National Aeronautics and Space Administration
