Millimeter Wave Passive And Active Sensors For Terrain Mapping

A 35 GHz dual Passive/Active Mode (PAM) sensor has been developed for a wide variety of air-to-ground imaging applications. The sensor measures radiometric temperature with a sensitivity of 2°K in the passive mode and terrain altitude to a resolution of 20 feet in the active mode. The sensor consists of a small 25 cubic inch ruggedized RF transceiver packaged on the back side of a 12 inch parabolic antenna providing a 2° one-way beamwidth. The system is designed to scan an angle of ±20° at 160°/sec about nadir in the cross range axis to the platform. In the active mode, terrain altitude is measured from 3,000 ft. to 30,000 ft. In the passive mode, radiometric temperature imaging has been accomplished up to altitudes of 54,000 ft. This paper presents an overview of the fundamentals of operation, a description of the advanced PAM sensor, signal-to-noise ratio performance and system measurement accuracy. Examples of airborne test data are included.