Establishing analytical criteria for selection of sites for calibration of spaceborne laser altimeters

The expected launch of spaceborne laser altimeters and the accuracy demands of derived products raise the need for post-launch calibration/validation to verify the measurements and the performance of the instruments. In addition to deriving adequate procedures for calibrating the system it is necessary to identify suitable sites over which calibration parameters can be estimated in an optimal way. Although it is clear that the surface topography should have a direct influence on the estimated parameters it is not clear what exactly the effect is, and how it can be generalized into a rule for evaluating a site. Indeed, the option of using trial and error methods always exists but it is inefficient and does not generalize, especially when several sites should be evaluated. Analytical criteria that enable direct evaluation of a site are established. Results of several sites that were evaluated for the calibration of the Geoscience Laser Altimeter System (GLAS) demonstrate the application of this method.