Spaceborne Laser Altimeter Instrument Parameter Calibration

To take advantage of the unique observing capabilities of lidar technology, two NASA dedicated Earth observing laser altimeter missions are scheduled for launch in the near future: the Vegetation Canopy Lidar (VCL) and the Ice, Cloud and land Elevation Satellite (ICESat). To properly geolocate the surface returns it will be necessary to verify and calibrate pointing, ranging, timing and orbit parameters once the instrument is in orbit. In preparation for these spacborne lidar missions, detailed algorithms and methodologies have been developed and tested to precisely geolocate the surface returns. Rigorous laser direct altimetry, dynamic crossover and geolocation measurement models have been implemented within NASA’s state of the art Precision Orbit Determination (POD) and geodetic parameter estimation software, GEODYN. The algorithms and their implementation provide an integrated range residual analysis capability to simultaneously estimate orbit, pointing, ranging and timing parameters from a combined reduction of direct altimetry, dynamic crossover and spacecraft tracking data. The following is a brief overview of the integrated residual analysis methodology and implementation. In addition, results of simulations and error analyses along with the application of the technique to the processing of Shuttle Laser Altimeter (SLA) data will be briefly discussed. The topics discussed are detailed within several papers currently in print and in review. The following is meant simply as an overview and to provide the reader with the necessary background and references to pursue the work in more detail.