HR: 08:15h
AN: C31A-02 INVITED     [PDF]
TI: Overview of ICESat's Laser Measurements of Polar Ice, Atmosphere, Ocean, and Land
AU: * Zwally, H J
EM: jay.zwally@nasa.gov
AF: NASA Goddard SFC, Oceans & Ice Branch, Code 971, NASA Goddard SFC, Greenbelt, MD 20771 United States
AB: NASA's Ice, Cloud and Land Elevation Satellite (ICESat) mission was designed to measure changes in elevation of the Greenland and Antarctic ice sheets, vertical distributions of clouds and aerosols globally, land topography, vegetation canopy heights, and sea-ice elevations. Time-series of ice-sheet elevation changes will enable determination of the present-day mass balance of the ice sheets, study of associations between observed ice changes and polar climate, and estimation of the present and future contributions of the ice sheets to global sea level rise. ICESat was launched in January, 2003 and acquired science data for about 36 days from February 20 to March 29 with the first of three lasers of the Geoscience Laser Altimeter System (GLAS). Data acquisition with the second laser is scheduled to commence in mid-September. GLAS has a 1064 nm laser channel for surface altimetry with a designed range precision of about 10 cm. Vertical distributions of clouds and aerosols with 75 m resolution have been obtained with the 1064 nm channel and will be obtained with the more sensitive 532 nm channel after the 532 nm detectors are turned on in September. The laser footprints are about 60 m on the surface and are spaced at 172 m along-track. The on-board GPS receiver enables radial orbit determinations to an accuracy better than 5 cm. The star-tracking attitude-determination system should enable footprints to be located to 6 m horizontally when attitude calibration is completed. The orbital altitude is around 600 km at an inclination of 94 degrees with a 8-day repeat pattern for the calibration and validation period. After laser 2 is turned on, another 8-day cycle will be completed before going to a 91-day repeat orbit with a 33-day sub-cycle. The spacecraft attitude is planned to be controlled to point the laser beam to within $ñ$ 35 m of reference surface tracks over the ice sheets and to point off-nadir up to 5 degrees to targets of interest. ICESat was designed to operate for 3 to 5 years and was intended to be followed by successive missions to measure ice sheet changes for at least 15 years. Results from the initial 36 days of ICESat data demonstrate a unique capability to measure ice and land elevations with unprecedented accuracy, measure the vertical distributions of clouds and aerosols with an unprecedented sensitivity and global detail, measure vegetation canopy heights, and the elevations of sea ice. Data to be acquired at intervals of six months with the additional lasers should demonstrate the capability to measure ice sheet elevation changes to the planned accuracy of 1 cm/year, observe seasonal and interannual changes in global cloud cover, and other laser-unique capabilities.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 1600 GLOBAL CHANGE (New category)
DE: 1610 Atmosphere (0315, 0325)
DE: 1640 Remote sensing
DE: 1827 Glaciology (1863)
SC: Cryosphere [C]
MN: 2003 Fall Meeting