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DOWNSIZING THE ASTROBIOLOGY INDEX
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- CASSINI UPDATES
- Cassini-Huygens Mission Status Report
- Cassini Exposes Saturns Two-Face Moon
- Cassini Significant Events for 8-14 July 2004
- NASAS MARS ROVERS ROLL INTO MARTIAN WINTER
DOWNSIZING THE ASTROBIOLOGY INDEX By David J. Thomas 20 July 2004 The Astrobiology Index, Marsbugs' sister site, will be downsized somewhat starting this week. As the field of astrobiology continues to grow, keeping up with the number of available publications has become almost impossible. Thus, links to individual articles will no longer be available on the Index. Links to astrobiology-related internet sites, journal and other publications will remain available. I apologize for any inconvenience, but it simply has become unmanageable. Visit The Astrobiology Index at http://www.lyon.edu/projects/marsbugs/astrobiology/. CASSINI UPDATES NASA/JPL releases Cassini Significant Events for 1-7 July 2004 NASA/JPL release, 9 July 2004 The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, July 7. The Cassini spacecraft is in an excellent state of health and is 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. On-board activities this week included the successful completion of the Saturn Orbit Insertion (SOI) Critical Sequence, playback of all SOI telemetry and science data, Cassini's first Titan flyby, and acquisition of temperature and composition data for validation of the Titan atmospheric model to be used by the Huygens probe when released in December 2004. Solar Conjunction occurs when the Sun is between the spacecraft and Earth. This year it will last from July 5 through July 11, and is a time of reduced commanding and downlink capability. During this period the project will uplink a command file consisting of 10 no-op commands sent every 5 minutes, 10 to 20 times daily. The purpose of the test is to accumulate statistics for uplink reliability at decreased separation angles. Just prior to the start of conjunction, a relative timed IDAP to modify the telemetry mode was uplinked to the spacecraft. This allowed the Instrument teams to obtain real-time instrument "house keeping" data to confirm the state of their instruments. The spacecraft is in a normal state and will remain Earth pointed and quiescent throughout conjunction. Preliminary port#2 of Science Operations Plan (SOP) Implementation of tour sequences S31/S32 occurred this week. The delivered products were merged and reports delivered to the implementation team. The SOP Update process for S05 began this week, and the process for S04 completed. A handoff package was delivered to Uplink Operations. A kick-off meeting was then held as part of the S04 Science and Sequence Update Process, and the Sub-Sequence Generation integrated sequence products were released to the Sequence Team (ST). The integrated sequence products and DSN keyword file for S03 were released to the ST for review, and the instrument teams delivered their instrument expanded block spacecraft activity sequence files to the file repository. The final sequence products for S03 will be available next week, and the sequence approval meeting held the week after. S03 will go active on board the spacecraft on July 30. As reported last week, the Cassini Team successfully executed the SOI burn on June 30, 2004. This main engine burn slowed the spacecraft by 626.17 meters per second or about 2254.2 kilometers per hour and allowed the spacecraft to be captured by Saturn's gravity field. Unlike delta-V burns executed by other JPL spacecraft, Cassini's SOI burn was the first and only burn designed to achieve a change in the specific energy of the spacecraft, instead of a change in the spacecraft velocity. The "energy" algorithm used was proposed, developed, coded, and flight-tested by the SCO and Navigation teams. This maneuver was also unique in the history of JPL in that the burn direction was changed continuously with time. The SOI "steering" rate was about 0.008 degrees per second, for a total steering angle of about 46 deg. This is very close to the rotation rate of the hour hand of a clock. By "steering", the main engine thrust tracked approximately the Saturn-relative velocity of the spacecraft, and the efficiency of the SOI burn was improved. Less propellant was used as a result. Following SOI, the decision was made to cancel both Orbital Trim Maneuvers (OTM) 001 and 001a. It was determined that there was no significant propellant savings or mission benefits to be gained by performing these maneuvers. Raytheon, Cassini Outreach, and the Instrument Operations (IO) Imaging Science Subsystem (ISS) team located at JPL were involved in the rapid development and deployment of the public web site for Cassini raw ISS images. The site was rolled out on SOI day. IO/ISS supplied design expertise, image data and metadata, testing, and site documentation. Mission Assurance conducted a pair of Risk Team meetings to reassess risk to the probe mission. As a result, three new items were added to the Significant Risk List (SRL). There are no red risks in the SRL. All continue to be mitigated to either yellow or green. In addition, all risks related only to the Cruise portion of the mission and SOI were officially retired. The flight team continues to be excited and energized by the number of articles appearing regarding Cassini, and the interest and enthusiasm of the public. During 64 hours surrounding the SOI period the total number of web site hits were as follows: Total for Cassini traffic = 261,216,092 Mission web site (saturn.jpl.nasa.gov) = 136,595,464 Portal (nasa.gov/cassini) = 124,620,628 Cassini-Huygens Mission Status Report NASA/JPL release 2004-174, 12 July 2004 The Cassini spacecraft emerged from behind the Sun today after being in solar conjunction since July 5. The most recent spacecraft telemetry was acquired from the Deep Space Network's Goldstone tracking station near Barstow, CA, today. The spacecraft is in excellent health and operating normally.
NASA image advisory 2004-182, 15 July 2004 The moon with the split personality, Iapetus, presents a perplexing appearance in the latest images snapped by the Cassini spacecraft. One hemisphere of the moon is very dark, while the other is very bright. Scientists do not yet know the origin of the dark material or whether or not it is representative of the interior of Iapetus. 
The moon with the split personality, Iapetus, presents a puzzling appearance. One hemisphere of the moon is very dark, while the other is very bright. Whether the moon is being coated by foreign material or being resurfaced by material from within is not yet known. Iapetus (pronounced eye-APP-eh-tuss) is one of Saturn's 31 known moons. Its diameter is about one third that of our own moon at 1,436 kilometers (892 miles). This image was taken in visible light with the Cassini spacecraft narrow angle camera on July 3, 2004, from a distance of 3 million kilometers (1.8 million miles) from Iapetus. The brightness variations in this image are not due to shadowing, they are real. During Cassini's four-year tour, the spacecraft will continue to image Iapetus and conduct two close encounters. One of those encounters, several years from now, will be at a mere 1,000 kilometers (622 miles). Iapetus was discovered by the Italian-French astronomer Jean Dominique Cassini in 1672. He correctly deduced that the trailing hemisphere is composed of highly reflective material, while the leading hemisphere is strikingly darker. This sets Iapetus apart from Saturn's other moons and Jupiter's moons, which tend to be brighter on their leading hemispheres. Voyager images show that the bright side of Iapetus, which reflects nearly 50 percent of the light it receives, is fairly typical of a heavily cratered icy satellite. The leading side consists of much darker, redder material that has a reflectivity of only about 3 to 4 percent. One scenario for the outside deposit of material has dark particles being ejected from Saturn's little moon Phoebe and drifting inward to coat Iapetus. One observation lending credence to an internal origin is the concentration of material on crater floors, which is suggestive of something filling in the craters. Iapetus is odd in other respects. It is in a moderately inclined orbit, one that takes it far above and below the plane in which the rings and most of the moons orbit. It is less dense than many of the other satellites, which suggests a higher fraction of ice or possibly methane or ammonia in its interior. Cassini Significant Events for 8-14 July 2004 NASA/JPL release, 16 July 2004 The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, July 14. The Cassini spacecraft is in an excellent state of health and is 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. 
Cassini exited the Solar Conjunction period this week. Telecommunications performance was limited as expected due to the position of the Sun between the spacecraft and Earth. Full communications capability was restored once a 2-degree Sun-Earth-Probe separation angle was achieved. After conjunction all instruments were once again configured for science acquisition. On or about July 13, Cassini exited Saturn's magnetosphere and the Magnetospheric and Plasma Science instruments began to monitor the solar wind. The unique geometry of this period of high altitude and phase angles of ~100 degrees will allow the Ultraviolet Imaging Spectrograph to simultaneously measure Saturn's aurora and magnetosphere. On-board activities this week included a reaction wheel assembly bias, uplink of a ram flight software patch and table load for the Cassini Plasma Spectrometer, Probe Checkout (PCO) #14, and a test of the Probe Mission Timer Unit (MTU). This is the first checkout of the probe since Saturn Orbit Insertion. All probe instruments and the MTU are functioning properly. In preparation for probe release and relay, the checkout was utilized by members of the ground system to practice the generation of 30 minute IDRs and the monitoring of the data flow to the Huygens Probe Operations Center. 
The icy, cratered surface of Saturn's moon Dione shows more than just its sunlit side in these two processed versions of the same image. Members of the Cosmic Dust Analyzer (CDA) instrument team escorted an engineering model of the instrument to JPL where it was connected to a test bed in the Integrated Test Laboratory for flight software testing. Next week the ITL will resume Probe Relay testing. Official port#2 of Science Operations Plan (SOP) Implementation of tour sequences S31/S32 occurred this week. The products were merged and delivered to ACS for end-to-end pointing analysis. Preliminary port#1 of SOP Implementation of tour sequences S33/S34 also occurred this week. The files were merged and a report was delivered identifying issues to be worked. The S05 SOP Update process began this week, and an assessment meeting to review requested changes to S07 was held as part of the Aftermarket process. Initially it appears that all requested changes can fit within available resources. The Target Working Teams and Orbiter Science Teams will be reviewing the requests over the next two weeks and provide their recommendations at the decision meeting scheduled for July 27. 
The first artificial satellite in the Saturn system, the Cassini spacecraft, returned images of the natural moons following a successful insertion into orbit. This is an unmagnified view of the moon Rhea. With a diameter of 1,528 kilometers (950 miles) across, Rhea is Saturn's second largest moon. The Voyager spacecraft found that like Dione, Rhea has one of its hemispheres covered with bright, wispy streaks which may be water frost. The Huygens Probe Mission Risk Review was held on Wednesday, July 14. This was an external review convened to assess the risks and risk mitigation measures associated with the probe mission. The board was comprised of independent reviewers from JPL, other NASA centers, and industry. The review was very successful with positive closing comments from the board. All teams and offices supported this month's Cassini monthly management review. A Software Review/Certification Requirements meeting was held for CDA flight software (FSW) version 9.2.4. Two bug fixes were previously approved for this "patch" delivery. The next full delivery of this FSW is scheduled for Dec 2004, with uplink planned for post-Probe mission. 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 Office of Space Science, Washington, DC. JPL designed, developed and assembled the Cassini orbiter. For the latest images and more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. Contacts: Carolina Martinez Jet Propulsion Laboratory, Pasadena, CA Phone: 818-354-9382 Heidi Finn Cassini Imaging Central Laboratory for Operations Space Science Institute, Boulder, CO Phone: 720-974-5859 Additional articles on this subject are available at: http://www.astrobio.net/news/article1057.html http://www.astrobio.net/news/article1058.html http://www.astrobio.net/news/article1059.html http://www.astrobio.net/news/article1077.html http://cl.extm.us/?fe8c1c727162077e7c-fe28167073670175701c72 http://www.cnn.com/2004/TECH/space/07/03/saturn.cassini.ap/index.html http://www.cnn.com/2004/TECH/space/07/08/rings.update/index.html http://www.cnn.com/2004/TECH/space/07/16/saturn.cassini.ap/index.html http://science.nasa.gov/headlines/y2004/09jul_hailstorm.htm?list52260 http://www.space.com/scienceastronomy/titan_upclose_040703.html http://www.space.com/scienceastronomy/saturn_rings_040708.html http://www.space.com/scienceastronomy/cassini_dust_040712.html http://spaceflightnow.com/cassini/040712southpole.html http://spaceflightnow.com/cassini/040712status.html http://www.spacedaily.com/news/cassini-04zu.html http://www.spacedaily.com/news/saturn-titan-04o.html http://www.spacedaily.com/news/cassini-04zv.html http://www.spacedaily.com/news/cassini-04zw.html http://www.spacedaily.com/news/cassini-04zx.html http://www.spacedaily.com/news/cassini-04zy.html http://www.spacedaily.com/news/cassini-04zza.html http://spaceflightnow.com/cassini/040701science.html http://spaceflightnow.com/cassini/040702magnetosphere.html http://spaceflightnow.com/cassini/040702puzzles.html http://spaceflightnow.com/cassini/040703titanpix.html http://spaceflightnow.com/cassini/040707ringsuv.html http://spaceflightnow.com/cassini/040715iapetus.html http://www.universetoday.com/am/publish/saturns_southern_atmosphere.html http://www.universetoday.com/am/publish/first_view_rhea.html NASA'S MARS ROVERS ROLL INTO MARTIAN WINTER NASA/JPL release 2004-184 16 July 2004 As winter approaches on Mars, NASA's Opportunity rover continues to inch deeper into the stadium-sized crater dubbed "Endurance." On the other side of the planet, the Spirit rover found an intriguing patch of rock outcrop while preparing to climb up the "Columbia Hills" backward. This unusual approach to driving is part of a creative plan to accommodate Spirit's aging front wheel. Spirit, with an odometer reading of over 3.5 kilometers (2.2 miles), has already traveled six times its designed capacity. Its right front wheel has been experiencing increased internal resistance, and recent efforts to mitigate the problem by redistributing the wheel's lubricant through rest and heating have been only partially successful. 
The pointy features in this image may only be a few centimeters high and less than 1 centimeter (0.4 inches) wide, but they generate major scientific interest. Dubbed "Razorback," this chunk of rock sticks up at the edge of flat rocks in "Endurance Crater." Based on their understanding of processes on Earth, scientists believe these features may have formed when fluids migrated through fractures, depositing minerals. Fracture-filling minerals would have formed veins composed of a harder material that eroded more slowly than the rock slabs. Possible examination of these features using the instruments on NASA's Mars Exploration Rover Opportunity may further explain what these features have to do with the history of water on Mars. This false-color image was taken by the rover's panoramic camera. Image credit: NASA/JPL/Cornell. To cope with the condition, rover planners have devised a roundabout strategy. They will drive the rover backward on five wheels, rotating the sixth wheel only sparingly to ensure its availability for demanding terrain. "Driving may take us a little bit longer because it is like dragging an anchor," said Joe Melko, a rover engineer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "However, this approach will allow us to continue doing science much longer than we ever thought possible." 
This image taken by the navigation camera on the Mars Exploration Rover Opportunity shows the layers of bedrock that line the walls of "Endurance Crater." Opportunity has been inching down the crater walls, investigating distinct layers of rock for clues to Mars' buried past. The various layers are labeled here as "A" through "F." Targets within these layers, including millstone, are also indicated. Using its alpha particle X-ray spectrometer, Opportunity has discovered that the element chlorine increases in concentration dramatically with deepening layers. Opportunity will continue to roll deeper into Endurance to see if this puzzling trend continues. Scientists hope the new data will help them figure out how the presence of chlorine fits into the history of water at Endurance Crater. This image was taken on sol 134 (June 9, 2004). Image credit: NASA/JPL. On Thursday, July 15, Spirit successfully drove 8 meters (26 feet) north along the base of the Columbia Hills backward, dragging its faulty wheel. The wheel was activated about 10 percent of the time to surmount obstacles and to pull the rover out of trenches dug by the immobile wheel. Along the way, Spirit drove over what scientists had been hoping to find in the hills—a slab of rock outcrop that may represent some of the oldest rocks observed in the mission so far. Spirit will continue to drive north, where it likely will encounter more outcrops. Ultimately, the rover will drive east and hike up the hills backward using all six wheels. "A few months ago, we weren't sure if we'd make it to the hills, and now here we are preparing to drive up into them," said Dr. Matt Golombek, a rover science-team member from JPL. "It's very exciting." For the past month, the Spirit rover has been parked near several hematite-containing rocks, including "Pot of Gold," conducting science studies and undergoing a long-distance "tune-up" for its right front wheel. Driving with the wheel disabled means that corrections might have to be made to the rover's steering if it veers off its planned path. This limits Spirit's accuracy, but rover planners working at JPL's rover test facility have come up with some creative commands that allow the rover to auto-correct itself to a limited degree. As Spirit prepares to climb upward, Opportunity is rolling downward. Probing increasingly deep layers of bedrock lining the walls of Endurance Crater at Meridiani Planum, the rover has observed a puzzling increase in the amount of chlorine. Data from Opportunity's alpha particle X-ray spectrometer show that chlorine is the only element that dramatically rises with deepening layers, leaving scientists to wonder how it got there. "We do not know yet which element is bound to the chlorine," said Dr. Jutta Zip Institute for Chemistry, Mainz, Germany. Opportunity will roll down even farther into the crater in the next few days to see if this trend continues. It also will investigate a row of sharp, teeth-like features dubbed "Razorback," which may have formed when fluid flowed through cracks, depositing hard minerals. Scientists hope the new data will help put together the pieces of Meridiani's mysterious and watery past. "Razorback may tell us more about the history of water at Endurance Crater," said Dr. Jack Farmer, a rover science-team member from Arizona State University. Rover planners are also preparing for the coming martian winter, which peaks in mid-September. Dwindling daily sunshine means the rovers will have less solar power and take longer to recharge. Periods of rest and "deep sleep" will allow the rovers to keep working through the winter at lower activity levels. Orienting the rovers' solar panels toward the north will also elevate power supplies. "The rovers might work a little bit more every day, or a little bit more every other day. We will see how things go and remain flexible," said Jim Erickson, project manager for the Mars Exploration Rover mission. JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Office of Space Science, Washington, DC. Images and additional information about the project are available on the Internet at http://marsrovers.jpl.nasa.gov and http://athena.cornell.edu. Daily MER updates are available at: http://marsrovers.jpl.nasa.gov/mission/status_spirit.html http://marsrovers.jpl.nasa.gov/mission/status_opportunity.html
Whitney Clavin Jet Propulsion Laboratory, Pasadena, CA Phone: 818-354-4673 Donald Savage NASA Headquarters, Washington, DC Phone: 202-358-1727
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