High temporal resolution laser radar tomography for long range target identification

The Air Force Electro Optics Division is pursuing advanced laser target identification technologies under its Enhanced Recognition and Sensing Ladar (ERASER) program. Long range, eyesafe target identification is of central importance in many regional operations. Building on advancements in laser sources, detectors1 and signal processing, direct detection ladar can provide ID well beyond the range of conventional imaging sensors. High temporal resolution laser radar can produce range resolved (ID) scattering profiles, which are unique to each aircraft relatively independent of target range2,3. This allows a variety of ID techniques to be applied at ranges well beyond the resolution limits of comparably sized imaging apertures. The ID profiles can be applied to automatic target recognition systems for classification and identification. However, in-class variation as well as large numbers of unclassified targets may limit these techniques. In this paper, we investigate the use of tomographic reconstruction to enhance long range identification. The reconstruction is based on compilations of ID signatures obtained at various angles due to relative target sensor motion. We describe the ladar system used to measure the ID returns of an F-4 aircraft. Based on the measured capabilities of the ERASER ladar, we use the IRMA computer model to generate sets of data consistent with the measured ladar data. Finally, we utilize the filtered back-projection method to investigate the reconstruction model data for both the ideal and limited-data cases.