From: baalke@zagami.jpl.nasa.gov   
      
   David Steitz/Elvia Thompson   
   Headquarters, Washington                   October 6, 2003   
   (Phone: 202/358-1730/1696)   
      
   Cynthia M. O'Carroll   
   Goddard Space Flight Center, Greenbelt, Md.   
   (Phone: 301/614-5563)   
      
   RELEASE: 03-319   
      
   ICESAT'S LASERS MEASURE ICE, CLOUDS AND LAND ELEVATIONS   
      
        NASA's Ice, Cloud and land Elevation Satellite (ICESat)   
   has resumed measurements of the Earth's polar ice sheets,   
   clouds, mountains and forests with the second of its three   
   lasers. Crisscrossing the globe at nearly 17,000 miles per   
   hour, this new space mission is providing data with   
   unprecedented accuracy on the critical third dimension of the   
   Earth, its vertical characteristics.   
      
   "The first set of laser measurements is revealing features of   
   the polar ice sheets with details never seen before, and is   
   detecting dust storms, cloud heights, tree heights and smoke   
   from forest fires in new and exciting ways," said Jay Zwally,   
   ICESat Project Scientist at NASA's Goddard Space Flight   
   Center, Greenbelt, Md.   
      
   The principal mission of ICESat is to measure the surface   
   elevation of the large ice sheets covering Antarctica and   
   Greenland. Measurements of elevation-change over time will   
   show whether the ice sheets are melting or growing as the   
   Earth's climate undergoes natural and human-induced changes.   
      
   The Geoscience Laser Altimeter System (GLAS) instrument on   
   ICESat sends short pulses of green and infrared light though   
   the sky 40 times a second, all over the globe, and collects   
   the reflected laser light in a one-meter telescope. The   
   elevation of the Earth's surface and the heights of clouds   
   and aerosols in the atmosphere are calculated from both   
   precise measurements of the travel time of the laser pulses,   
   and ancillary measurements of the satellite's orbit and   
   instrument orientation. This marks the first time any   
   satellite has made vertical measurements of the Earth through   
   the use of an onboard light source.   
      
   Operating in a near-polar orbit, ICESat is adding to our   
   understanding of the mass-balance of the Greenland and   
   Antarctic ice sheets. ICESat's first topographic profiles   
   across Antarctica revealed details of features such as the   
   ice streams of the Siple Coast and the Amery Ice Shelf, as   
   well as the atmospheric phenomena above them.   
      
   ICESat is also making unique measurements of cloud heights   
   and global distribution. ICESat detects distributions of   
   aerosols from sources such as dust storms and forest fires.   
   And because its laser pulses continuously, ICESat also   
   measures the Earth's topography with high accuracy.   
      
   "ICESat has already demonstrated the unique capability of   
   lasers to make a variety of Earth Science measurements. When   
   the calibration experiments are completed, we believe the   
   accuracy and sensitivity will exceed previous capabilities by   
   nearly an order of magnitude," stated Bob Schutz, GLAS   
   Science Team Leader, of the University of Texas at Austin.   
      
   ICESat was launched January 12, 2003, on a Boeing Delta II   
   rocket from Vandenberg Air Force Base, Calif. On March 29,   
   ICESat's Laser 1 unexpectedly stopped working after providing   
   36 days of data. NASA will issue a report shortly on the   
   reason for the anomaly.   
      
   "Despite the problem with the first laser, ICESat is   
   providing a new perspective on elements within the Earth   
   System with amazing accuracy. We are especially looking   
   forward to the information this capability will provide on   
   how the polar ice sheets are changing," said Waleed Abdalati,   
   ICESat Program Scientist at NASA Headquarters, Washington.   
      
   The ICESat scientists will convene a special session to   
   present the latest results from ICESat at the 2003 Fall   
   Meeting of the American Geophysical Union in San Francisco.   
      
   ICESat is the latest in a series of NASA's Earth observation   
   spacecraft designed to study the environment of our home   
   planet and how it may be changing. NASA's Earth Science   
   Enterprise is dedicated to understanding the Earth as an   
   integrated system and applying Earth System Science to   
   improve prediction of climate, weather and natural hazards   
   using the unique vantage point of space.   
      
   For more information and images on the Internet, visit:   
      
   http://www.gsfc.nasa.gov/topstory/2003/0920icesatfirst.html   
   http://icesat.gsfc.nasa.gov   
      
   For more information about NASA's Earth Science Enterprise on   
   the Internet, visit:   
      
   http://www.earth.nasa.gov   
      
   -end-   
      
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