HR: 14:15h
AN: C43B-04    [Abstracts]
TI: Space-based Swath Imaging Laser Altimeter for Cryospheric Topographic and Surface Property Mapping
AU: Abshire, J
EM: James.B.Abshire@nasa.gov
AF: NASA Goddard Space Flight Center, Mail Code 690, Greenbelt, MD 20771 United States
AU: * Harding, D
EM: David.J.Harding@nasa.gov
AF: NASA GSFC, Mail Code 698,
AU: Shuman, C
EM:
AF: NASA GSFC, Mail Code 614.1,
AU: Sun, X
EM:
AF: NASA GSFC, Mail Code 694,
AU: Dabney, P
EM:
AF: NASA GSFC, Mail Code 694,
AU: Krainak, M
EM:
AF: NASA GSFC, Mail Code 694,
AU: Scambos, T
EM:
AF: University of Colorado, National Snow and Ice Data Center, Boulder, CO
AB: Uncertainties in the response of the Greenland and Antarctic polar ice sheets to global climatic change inspired the development of ICESat/GLAS as part of NASA's Earth Observing System. ICESat's primary purpose is the measurement of ice sheet surface elevation profiles with sufficient accuracy, spatial density, and temporal coverage so that elevation changes can be derived with an accuracy of <1.5 cm/year for averages of measurements over the ice sheets with areas of 100 x 100 km. The primary means to achieve this elevation change detection is spatial averaging of elevation differences at cross-overs between ascending and descending profiles in areas of low ice surface slope. Insights gained during the development of GLAS, its orbital operations, and the calibration and scientific utilization of ICESat data have contributed to an approach for a next-generation laser altimeter for global measurements. Cryospheric scientific drivers for the approach include a greater recognition of (1) the importance of documenting processes leading to ice mass change that vary on short spatial scales (e.g., snowfall, melt events and runoff, rainfall, iceberg discharge, snow drift removal), (2) elevation changes in the higher-relief margins of ice sheets near major outlet glaciers, (3) the importance of ice stream dynamics within ice sheets, (4) the role of accelerated ice cap and mountain glacier mass loss to sea level rise, and (5) energy-balance feedbacks of sea ice loss and its potential disruptive impact on climate in the high northern latitudes. We are developing a new swath imaging laser altimeter mission concept for topographic mapping from space, with a mission lifetime goal of 7-10 years, to provide precise elevation and surface character image data for global measurements of glaciers, ice sheets, and sea ice. The measurement technique produces measurements in ~10 m spots, which are contiguous along and cross track, in a swath approximately 1 km wide. The approach measures an echo pulse waveform for each spot, via modulated fiber laser transmitters and photon-counting detectors, in a highly redundant push-broom configuration operating near 1060 nm. The pulse code modulated approach is well suited for the output characteristics of fiber lasers. Calculations show the vertical elevations will be measured to < 10 cm for each spot. The swath width, in combination with precision spacecraft pointing, allows well-overlapped repeat coverage of temporally variable cryospheric features, a key to determining trends in mass balance. Measuring the range-resolved intensity and depolarization of the backscatter signal at 1060 nm, and potentially also at a frequency-doubled wavelength of 530 nm, enables additional estimates to be made about the physical state of snow, ice, water and land surfaces.
DE: 1243 Space geodetic surveys
DE: 1640 Remote sensing
DE: 1655 Water cycles (1836)
DE: 1694 Instruments and techniques
SC: Cryosphere [C]
MN: 2005 Joint Assembly