SAR/MTI from helicopters

MTI/SAR is a well established technique for airborne surveillance. In a helicopter these two modes of operation can be combined as well. The helicopter can also easily move in the vertical direction, making SAR mapping of the height profile of the ground surface possible. In this paper, MTI/SAR from a helicopter is studied in more detail. Relationships are developed between the involved parameters, and the performance is displayed in some examples. Phase error compensation is needed by IMU or autofocusing due to the non-linear movement of the antenna along the SAR path. Highly improved mapping performance can be achieved by using an ESA with multiple beam generation, or high speed scanning. For high resolution mapping in three dimensions interferometric SAR is needed.