Full-scale testing and platform stabilization of a scanning lidar system for planetary landing

In August 2007, the engineering model of the Rendezvous Lidar System (RLS) was tested at the Sensor Test Range Facility that has been developed at NASA Langley Research Center for the calibration and characterization of 3-D imaging sensors. The three-dimensional test pattern used in this characterization is suitable for an empirical verification of the resolving capability of a lidar for both mid-range terminal rendezvous and hazard avoidance landing. The results of the RLS lidar measurements are reported and compared with image frames generated by a lidar simulator with an Effective Instantaneous Field of View (EIFOV) consistent with the actual scanning time-of-flight lidar specifications. These full-scale tests demonstrated the resolving capability of the lidar under static testing conditions. In landing operations, even though the lidar has a very short exposure time on a per-pulse basis, the dynamic motion of a lander spacecraft with respect to the landing site will cause pulse-to-pulse imaging distortion. MDA, Optech, and NGC Aerospace have teamed together to resolve this issue using motion compensation (platform stabilization) and motion correction (platform residual correction) techniques. Platform stabilization permits images with homogenous density to be generated so that no safe landing sites will be missed; platform residual errors that are not prevented by this stabilization are then corrected in the measurement data prior to map generation. The results of recent developments in platform stabilization and motion correction are reported and discussed in the context of total imaging error budget.