HR: 16:45h
AN: G54A-04    [Abstracts]
TI: Laser Altimeter Mission Design Constraints from ICESat Observations of 1064 nm Apparent Surface Reflectance
AU: * Carabajal, C C
EM: Claudia.C.Carabajal@nasa.gov
AF: SIGMA SPACE Corp.@NASA/Goddard Space Flight Center, Mail Code 698 Planetary Geodynamics Laboratory, Greenbelt, MD 20771, United States
AU: Harding, D J
EM: David.J.Harding@nasa.gov
AF: NASA/Goddard Space Flight Center, Mail Code 698 Planetary Geodynamics Laboratory, Greenbelt, MD 20771, United States
AU: Shuman, C A
EM: Christopher.A.Shuman@nasa.gov
AF: UMBC Goddard Earth Science and Technology Center, NASA/Goddard Space Flight Center Mail Code 698 Planetary Geodynamics Laboratory, Greenbelt, MD 20771, United States
AU: Suchdeo, V P
EM: Vijay.P.Suchdeo@nasa.gov
AF: SIGMA SPACE Corp.@NASA/Goddard Space Flight Center, Mail Code 614.1 Cryospheric Sciences Branch, Greenbelt, MD 20771, United States
AB: Performance of laser altimeters, including the probability of detecting a return from the surface and the precision of the resulting range measurement, depends on instrumental and environmental parameters. Environmental conditions can be expressed as apparent surface reflectance at the laser wavelength, combining atmospheric transmission (a function of cloud cover and aerosols) and surface "hot spot" retro-reflectance (i.e., at 0 degrees phase angle, with parallel illumination and view angles). We are using data acquired by the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud and land Elevation Satellite (ICESat) to establish probability distribution functions for 1064 nm apparent surface reflectance. GLAS was designed to range to the Earth's surface through thin to moderately dense clouds and aerosols, up to an optical depth of 2 (13% one way transmission). Its apparent surface reflectance data, therefore, provides valuable information relevant to the design of future orbital laser altimeters such as those recommended by the National Research Council in their Earth Science Decadal Survey report to NASA and NOAA (the ICESat-II, DESDynI and LIST missions). We are characterizing GLAS-observed apparent surface reflectance as it varies geographically, seasonally, and with the time of day, correcting for several instrumental artifacts (detector response non-linearity, saturation, and field-of- view shadowing). We will present statistics on apparent reflectance and the number of laser pulses that do not yield a surface return due to dense clouds and/or aerosols for the various ICESat observation periods for selected regions with different atmospheric and land cover characteristics. The selected regions include areas where laser altimeter observations of the surface are limited by frequent cloud cover, including polar latitudes important for ice sheet mass balance purposes and equatorial latitudes important for quantifying biomass storage and fluxes in tropical rain forests. This fundamental data on the measurement environment can be used in trade studies of laser altimeter mission designs, operating in the near-infrared, and to quantify expected performance attributes such as the spatial distribution, density and accuracy of surface returns accumulated through time.
DE: 1209 Tectonic deformation (6924)
DE: 1294 Instruments and techniques
DE: 8110 Continental tectonics: general (0905)
DE: 8488 Volcanic hazards and risks
DE: 8494 Instruments and techniques
SC: Geodesy [G]
MN: 2007 Fall Meeting