Laser radar system demonstration: System requirements review, second demonstration receiver

A conceptual design is currently being developed for a sensor system which is capable of detecting both large and small targets using a pulsed transmitter and high bandwidth receiver. The mission scenario for the large target requires that it first be detected with a small false alarm rate, and immediately classified with a few additional transmitter pulses. The sensor must also be capable of detecting small targets with a low false alarm rate. Because a number of naturally occurring objects can cause false alarms, it is believed that the most effective means for mitigating these false alarms is to complete the classification or identification of the small target immediately following detection. This must be accomplished with negligible effect on the overall search rate. It is desirable, but not presently a requirement, that the sensor system be capable of detecting these targets also. Two conceptual approaches were developed to meet the foregoing performance requirements of the desired sensor system. Both use short-pulse lasers to illuminate the target. In the first approach a high resolution image is created using a single range gate of reflected or backscattered light. The images have a large number of pixels, with square arrays of the order of 128x128 to 256x256. In the second approach, a more limited array of time-resolved pixels is used to gather three-dimensional data of the region containing the target. In the time-resolved approach, the array sizes are more limited because of the requirement for multiple channels of high-speed electronics.