The principal use of the microwave sensor is for protection of wide, open spaces. With its long range and wide volumetric pattern it can be used to great effect in warehouses, halls and galleries.

Active microwave sensors can be further divided into four general classes: syn- thetic aperture radar (SAR) systems, scatterometers, altimeters, and weather radars. The latter systems typically use real-aperture antennas while SAR is based on syn- thetic aperture antenna processing techniques.

The moisture sensor inside the microwave detects the steam emitted from the food when it is cooking and automatically adjusts the cooking time. This feature allows the cooking of any type of canned vegetable from a four ounce serving to a full sixteen ounce can.

Typical examples of passive sensors are Landsat OLI/TIRS and MODIS. Radar has been used to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain.