A SAR emits pulses of radio waves repeatedly from a SAR sensor mounted on a platform to objects to be observed, and receives the radio waves that are reflected by the objects. The SAR then generates a SAR image on the basis of position information of the platform acquired when radio waves are transmitted, position information of the platform acquired when the radio waves that are reflected by an object to be observed are received, and received radio wave signals. Note that received signals of radio waves that are transmitted and received while a platform follows a trajectory that is planned (hereinafter referred to as an planned trajectory) are supposed to be used to generate a SAR image.
In a case where the platform is, for example, a flying body such as an aircraft, however, the platform may be affected by wind or the like and follow a trajectory different from the planned trajectory.
To deviate from the planned trajectory to the trajectory that the platform actually follows (hereinafter referred to as an actual trajectory) is referred to as motion, and a SAR image generated from received radio wave signals obtained when motion has occurred may be blurred. Thus, when motion has occurred, a motion compensation process is performed to make transmission/reception times of radio waves that are transmitted to an observation object and received from the observation object upon reflection, the phases of the received radio wave signals, and the like closer to values that would be obtained from the platform following the planned trajectory.
A SAR of related art performs the motion compensation process on all the signals used for generation of a SAR image to reduce blurring of the SAR image as described in Patent Literature 1, for example.