Microwave radiometers are the only sensors capable of passive, adverse weather, day-night operation. With operating principles similar to infrared (IR) sensors, microwave radiometers can produce imagery superior to that of high resolution radars on an equal resolution basis. They also provide a low cost, small alternative to radar which can give pod systems, remotely piloted vehicles (RPV), and aircraft an adverse weather capability where the size, cost and complexity of a radar system producing the same quality of imagery could not be accommodated. The phenomenology associated with microwave radiometric (MICRAD) imagery provides a different measurement of target characteristics and thus, increased target identification capability when utilized in multisensor systems. However, MICRAD systems of acceptable performance have only recently been developed.