Rapid, Globally Contiguous, High Resolution, 3d Topographic Mapping of Planetary Moons Using a Scanning Photon-counting Lidar

Introduction: Photon-counting lidar altimeters and imagers are the most efficient possible since each range measurement requires only one detected photon as opposed to hundreds or thousands in conventional laser pulse time of flight (TOF) altimeters. The GLAS altimeter on ICESat-I, for example, has a minimum detectable signal corresponding to roughly 100 photoelectrons but can produce in excess of 10,000 detected photoelectrons per pulse from high reflectance surfaces under extremely clear atmospheric conditions. Thus, single photon sensitivity translates to up to four orders of magnitude more imaging capability. Furthermore, single photon sensitivity combined with multistop timing capability enables the lidar to penetrate semiporous obscurations such as vegetation, ground fog or haze, thin clouds, water columns, etc. and makes contiguous, high resolution topographic mapping on a single overflight possible with modest laser powers and telescope apertures – even from orbital altitudes.