Modelocked-Laser Laser Radar Performance in the Detection of TMD and NMD Targets

摘要

Ultra compact mode locked CO2 lasers and mode locked Nd:fiber lasers are beingdeveloped for Theater Missile Defense (TMD) and National Missile Defense (NMD) applications. These lasers produce a coherent train of narrow pulses which may be used in a coherent laser radar (ladar) to form an image of a possible target. The distance to the target is irrelevant as long as there is enough received energy. These images are known as range Doppler, range resolved Doppler, or inverse synthetic aperture radar (ISAR) images. The down range image resolution is given by the micro pulse width multiplied by c/2, and the image Doppler resolution is given by the reciprocal total pulse length consisting of many hundreds of micro pulses. In this paper we briefly review previous work on the target range Doppler image features which are useful for target discrimination, and then we examine the detection of the target under low signal conditions given passive sensor or radar handover range and velocity information which contains errors. A Gaussian mode radiometry analysis is presented, the range Doppler image formation process is reviewed, and the effects of target speckle, pointing errors, and atmospheric turbulence are discussed. A metric for determining a target detection, under these low signal initial conditions, is proposed.