May 30 2013

From The Space Library

RELEASE: 13-160 - LANDSAT 8 SATELLITE BEGINS WATCH --WASHINGTON -- NASA transferred operational control Thursday of the Landsat 8 satellite to the U.S. Geological Survey (USGS) in a ceremony in Sioux Falls, S.D. The event marks the beginning of the satellite's mission to extend an unparalleled four-decade record of monitoring Earth's landscape from space. Landsat 8 is the latest in the Landsat series of remote-sensing satellites, which have been providing global coverage of landscape changes on Earth since 1972. The Landsat program is a joint effort between NASA and USGS. NASA launched the satellite Feb. 11 as the Landsat Data Continuity Mission (LDCM). Since then, NASA mission engineers and scientists, with USGS collaboration, have been putting the satellite through its paces -- steering it into its orbit, calibrating the detectors, and collecting test images. Now fully mission-certified, the satellite is under USGS operational control. Landsat is a centerpiece of NASA's Earth Science program, said NASA Administrator Charles Bolden in Washington. "Landsat 8 carries on a long tradition of Landsat satellites that for more than 40 years have helped us learn how Earth works, to understand how humans are affecting it and to make wiser decisions as stewards of this planet." Beginning Thursday, USGS specialists will collect at least 400 Landsat 8 scenes every day from around the world to be processed and archived at the USGS Earth Resources Observation and Science Center in Sioux Falls. The newest satellite joins Landsat 7, which launched in 1999 and continues to collect images. Since 2008, USGS has provided more than 11 million current and historical Landsat images free of charge to users over the Internet. We are very pleased to work with NASA for the good of science and the American people, said U.S. Interior Secretary Sally Jewell in Washington. "The Landsat program allows us all to have a common, easily accessible view of our planet. This is the starting point for a shared understanding of the environmental challenges we face." Remote-sensing satellites such as the Landsat series help scientists observe the world beyond the power of human sight, monitor changes to the land that may have natural or human causes, and detect critical trends in the conditions of natural resources. The 41-year Landsat record provides global coverage at a scale that impartially documents natural processes such as volcanic eruptions, glacial retreat and forest fires and shows large-scale human activities such as expanding cities, crop irrigation and forest clear-cuts. The Landsat Program is a sustained effort by the United States to provide direct societal benefits across a wide range of human endeavors including human and environmental health, energy and water management, urban planning, disaster recovery, and agriculture. With Landsat 8 circling Earth 14 times a day, and in combination with Landsat 7, researchers will be able to use an improved frequency of data from both satellites. The two observation instruments aboard Landsat 8 feature improvements over their earlier counterparts while collecting information that is compatible with 41 years of land images from previous Landsat satellites.

RELEASE: 13-164 - NASA'S GRAIL MISSION SOLVES MYSTERY OF MOON'S SURFACE GRAVITY --PASADENA, Calif. -- NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission has uncovered the origin of massive invisible regions that make the moon's gravity uneven, a phenomenon that affects the operations of lunar-orbiting spacecraft. Because of GRAIL's findings, spacecraft on missions to other celestial bodies can navigate with greater precision in the future. GRAIL's twin spacecraft studied the internal structure and composition of the moon in unprecedented detail for nine months. They pinpointed the locations of large, dense regions called mass concentrations, or mascons, which are characterized by strong gravitational pull. Mascons lurk beneath the lunar surface and cannot be seen by normal optical cameras. GRAIL scientists found the mascons by combining the gravity data from GRAIL with sophisticated computer models of large asteroid impacts and known detail about the geologic evolution of the impact craters. The findings are published in the May 30 edition of the journal Science. GRAIL data confirm that lunar mascons were generated when large asteroids or comets impacted the ancient moon, when its interior was much hotter than it is now, said Jay Melosh, a GRAIL co-investigator at Purdue University in West Lafayette, Ind., and lead author of the paper. "We believe the data from GRAIL show how the moon's light crust and dense mantle combined with the shock of a large impact to create the distinctive pattern of density anomalies that we recognize as mascons." The origin of lunar mascons has been a mystery in planetary science since their discovery in 1968 by a team at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. Researchers generally agree mascons resulted from ancient impacts billions of years ago. It was not clear until now how much of the unseen excess mass resulted from lava filling the crater or iron-rich mantle upwelling to the crust. On a map of the moon's gravity field, a mascon appears in a target pattern. The bulls-eye has a gravity surplus. It is surrounded by a ring with a gravity deficit. A ring with a gravity surplus surrounds the bulls-eye and the inner ring. This pattern arises as a natural consequence of crater excavation, collapse and cooling following an impact. The increase in density and gravitational pull at a mascon's bulls-eye is caused by lunar material melted from the heat of a long-ago asteroid impact. Knowing about mascons means we finally are beginning to understand the geologic consequences of large impacts, Melosh said. "Our planet suffered similar impacts in its distant past, and understanding mascons may teach us more about the ancient Earth, perhaps about how plate tectonics got started and what created the first ore deposits." This new understanding of lunar mascons also is expected to influence planetary geology well beyond that of Earth and our nearest celestial neighbor. Mascons also have been identified in association with impact basins on Mars and Mercury, said GRAIL principal investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. "Understanding them on the moon tells us how the largest impacts modified early planetary crusts." Launched as GRAIL A and GRAIL B in September 2011, the probes, renamed Ebb and Flow, operated in a nearly circular orbit near the poles of the moon at an altitude of about 34 miles (55 kilometers) until their mission ended in December 2012. The distance between the twin probes changed slightly as they flew over areas of greater and lesser gravity caused by visible features, such as mountains and craters, and by masses hidden beneath the lunar surface. JPL managed GRAIL for NASA's Science Mission Directorate in Washington. The mission was part of the Discovery Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. NASA's Goddard Space Flight Center, in Greenbelt, Md., manages the Lunar Reconnaissance Orbiter. Operations of the spacecraft's laser altimeter, which provided supporting data used in this investigation, is led by the Massachusetts Institute of Technology in Cambridge. Lockheed Martin Space Systems in Denver built GRAIL.

RELEASE: 13-165 - RADIATION MEASURED BY NASA'S CURIOSITY ON VOYAGE TO MARS HAS IMPLICATIONS FOR FUTURE HUMAN MISSIONS --WASHINGTON -- Measurements taken by NASA's Mars Science Laboratory (MSL) mission as it delivered the Curiosity rover to Mars in 2012 are providing NASA the information it needs to design systems to protect human explorers from radiation exposure on deep-space expeditions in the future. MSL's Radiation Assessment Detector (RAD) is the first instrument to measure the radiation environment during a Mars cruise mission from inside a spacecraft that is similar to potential human exploration spacecraft. The findings will reduce uncertainty about the effectiveness of radiation shielding and provide vital information to space mission designers who will need to build in protection for spacecraft occupants in the future. As this nation strives to reach an asteroid and Mars in our lifetimes, we're working to solve every puzzle nature poses to keep astronauts safe so they can explore the unknown and return home, said William Gerstenmaier, NASA's associate administrator for human exploration and operations in Washington. "We learn more about the human body's ability to adapt to space every day aboard the International Space Station. As we build the Orion spacecraft and Space Launch System rocket to carry and shelter us in deep space, we'll continue to make the advances we need in life sciences to reduce risks for our explorers. Curiosity's RAD instrument is giving us critical data we need so that we humans, like the rover, can dare mighty things to reach the Red Planet." The findings, which are published in the May 31 edition of the journal Science, indicate radiation exposure for human explorers could exceed NASA's career limit for astronauts if current propulsion systems are used. Two forms of radiation pose potential health risks to astronauts in deep space. One is galactic cosmic rays (GCRs), particles caused by supernova explosions and other high-energy events outside the solar system. The other is solar energetic particles (SEPs) associated with solar flares and coronal mass ejections from the sun. Radiation exposure is measured in units of Sievert (Sv) or milliSievert (one one-thousandth Sv). Long-term population studies have shown exposure to radiation increases a person's lifetime cancer risk. Exposure to a dose of 1 Sv, accumulated over time, is associated with a 5 percent increase in risk for developing fatal cancer. NASA has established a 3 percent increased risk of fatal cancer as an acceptable career limit for its astronauts currently operating in low-Earth orbit. The RAD data showed the Curiosity rover was exposed to an average of 1.8 milliSieverts of GCR per day on its journey to Mars. Only about 5 percent of the radiation dose was associated with solar particles because of a relatively quiet solar cycle and the shielding provided by the spacecraft. The RAD data will help inform current discussions in the United States medical community, which is working to establish exposure limits for deep-space explorers in the future. In terms of accumulated dose, it's like getting a whole-body CT scan once every five or six days, said Cary Zeitlin, a principal scientist at the Southwest Research Institute (SwRI) in San Antonio and lead author of the paper on the findings. "Understanding the radiation environment inside a spacecraft carrying humans to Mars or other deep space destinations is critical for planning future crewed missions." Current spacecraft shield much more effectively against SEPs than GCRs. To protect against the comparatively low energy of typical SEPs, astronauts might need to move into havens with extra shielding on a spacecraft or on the Martian surface, or employ other countermeasures. GCRs tend to be highly energetic, highly penetrating particles that are not stopped by the modest shielding provided by a typical spacecraft. Scientists need to validate theories and models with actual measurements, which RAD is now providing, said Donald M. Hassler, a program director at SwRI and principal investigator of the RAD investigation. "These measurements will be used to better understand how radiation travels through deep space and how it is affected and changed by the spacecraft structure itself. The spacecraft protects somewhat against lower energy particles, but others can propagate through the structure unchanged or break down into secondary particles." After Curiosity landed on Mars in August, the RAD instrument continued operating, measuring the radiation environment on the planet's surface. RAD data collected during Curiosity's science mission will continue to inform plans to protect astronauts as NASA designs future missions to Mars in the coming decades. SwRI, together with Christian Albrechts University in Kiel, Germany, built RAD with funding from NASA's Human Exploration and Operations Mission Directorate and Germany's national aerospace research center, Deutsches Zentrum fur Luft- und Raumfahrt. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Science Laboratory Project. The NASA Science Mission Directorate at NASA Headquarters in Washington manages the Mars Exploration Program.

MEDIA ADVISORY: M13-088 - ACTOR JADEN SMITH FOCUSES ON EARTH SCIENCE IN A NEW NASA PSA --WASHINGTON -- Jaden Smith, star of Columbia Pictures' movie "After Earth," is featured in a new NASA public service announcement that describes the contributions of the agency's Earth science program to environmental awareness and exploration of our home planet. The public service announcement features imagery from "After Earth" as well as animations of Earth data from 17 orbiting NASA satellites. The satellites are making cutting-edge observations of the entire Earth system, including the atmosphere, oceans, land surface, and snow and ice. The observations are used by scientists worldwide to improve our understanding of our complex planet, better predict the future of our changing climate, and enhance life on Earth today. NASA has a fleet of satellites around the planet that keeps track of climate change and studies how humans are affecting the planet, Smith says in the public service announcement. "At NASA right now, scientists and engineers are working every day to help humans learn how to better care for their home so that we never have to leave." NASA Television will broadcast the announcement beginning Thursday, May 30. It is available to television and radio stations and other interested media outlets.