1 : An adaptive sensing system comprising: a passive sensor to receive electromagnetic radiation, an active sensor to emit and receive electromagnetic radiation, and circuitry that detects whether human beings or only objects other than human beings are present in a region of observation, and controls the active sensor and the passive sensor based on the detection of whether human beings or only objects other than human beings are present, wherein when the presence of a human being is detected in the region of observation, the passive sensor is activated and the detected human being is scanned by the passive sensor, the circuitry controlling the passive sensor so as to receive electromagnetic radiation from at least a first portion of the region of observation where the human being is detected, when the presence of an object other than a human being is detected in the region of observation, the active sensor is activated and the detected object other than a human being is scanned by the active sensor, the circuitry controlling the active sensor so as to transmit and receive electromagnetic radiation to and from at least a second portion of the region of observation where the object is detected, and the circuitry modifies an amount of one of power and field strength of the electromagnetic radiation output by the active sensor responsive to the detection of whether human beings or only objects other than human beings are present in the region of observation.