HR: 11:05h
AN: C31D-04    [PDF]
TI: Calibration and Validation of the ICESat Laser Altimeter
AU: * Magruder, L
EM: magruder@csr.utexas.edu
AF: Center for Space Research, University of Texas at Austin, 3925 West Braker Lane Suite 200, Austin, TX 78759 United States
AU: Silverberg, E
EM: ecsilverberg@att.net
AF: Center for Space Research, University of Texas at Austin, 3925 West Braker Lane Suite 200, Austin, TX 78759 United States
AU: Ricklefs, R
EM: ricklefs@csr.utexas.edu
AF: Center for Space Research, University of Texas at Austin, 3925 West Braker Lane Suite 200, Austin, TX 78759 United States
AU: Webb, C
EM: webb@csr.utexas.edu
AF: Center for Space Research, University of Texas at Austin, 3925 West Braker Lane Suite 200, Austin, TX 78759 United States
AU: Bae, S
EM: bae@csr.utexas.edu
AF: Center for Space Research, University of Texas at Austin, 3925 West Braker Lane Suite 200, Austin, TX 78759 United States
AU: Horstman, M
EM: rumalo@csr.utexas.edu
AF: Center for Space Research, University of Texas at Austin, 3925 West Braker Lane Suite 200, Austin, TX 78759 United States
AU: Urban, T
EM: urban@csr.utexas.edu
AF: Center for Space Research, University of Texas at Austin, 3925 West Braker Lane Suite 200, Austin, TX 78759 United States
AU: Schutz, B
EM: schutz@csr.utexas.edu
AF: Center for Space Research, University of Texas at Austin, 3925 West Braker Lane Suite 200, Austin, TX 78759 United States
AB: ICESat, the altimetry mission devoted to determination of temporal variations in the Polar Regions, launched in January of 2003. The satellite is in a nearly circular orbit with an inclination of 94 deg and a mean altitude of 600 km. The science goals of ICESat are to perform repeat elevation measurements over time with an accuracy of 1.5 cm/yr for a 100 km by 100 km area. Achievement of the science goals partly depends on the accurate determination of the laser direction as well as identifying any biases in the timing and/or range measurements. The pointing or directional information of the laser in the celestial reference frame is provided by an innovative CCD camera onboard ICESat. The laser pointing accuracy requirement is 1.5 arc seconds. The pointing information and the range data product combine to produce a measured altitude vector. The Earth illuminated spot location is the vector sum of the altitude vector and the precision orbit position vector in the terrestrial reference frame. In order to verify that the laser directional information is appropriately accurate, several experiments have been implemented during the initial 35+ days of laser operation. These experiments, performed at White Sands (New Mexico) and Bonneville (Utah), contribute to the validation of the scalar altitude measurement, the time of measurement and the position of the laser footprint to within 4.5 meters (1.5 arc second). The two methodologies that will be conducted at one or both of the aforementioned locations are an airborne camera system that will photograph at least one ICESat laser spot on the ground, and a ground detection array that will `capture' multiple spots on the surface. Both techniques will provide independent measurements for comparison to the onboard laser directional data and the measurement timing. During the initial laser operations period (Feb 20th - Mar 29th), photographs were acquired and analyzed for position determination. Although the ground array did not capture and time tag an ICESat footprint, the calibration activities assisted in tuning the implementation of off-nadir pointing commands and contributed to analysis of laser offset biases. An integral part of the verification of the scalar altitude measurement is the comparison to an independent airborne LIDAR survey over the White Sands area. Existing data has been crucial to ongoing analysis of the altimetry data products and the accuracies. Further refinement is expected when laser operations and the calibration activities resume.
DE: 1294 Instruments and techniques
SC: Cryosphere [C]
MN: 2003 Fall Meeting