SAR radar system

Claim 1

A wideband synthetic aperture radar (SAR) system for a vehicle moving above a planetary surface along a vehicle path and having a radar platform, comprising: position-determining means to determine the position of the vehicle, transmit means to repeatedly transmit radar signals that span at least an octave of bandwidth, the transmit means transmitting the radar signals from the vehicle towards the planetary surface, receive means to receive backscattered radar signals on the vehicle at different vehicle positions, processing equipment for transforming the received backscattered signals into an image of the planetary surface wherein the system uses a backprojection, and; wherein the processing equipment further performs the following functions; collects signal amplitudes over segments of the vehicle path in the form of synthetic subapertures of a synthetic aperture, the subapertures having a length at which closest points imaged on the planetary surface are in a far-field of said subapertures with respect to a wavelength, the wavelength being characteristic of the radar signal, synthesizes, from data obtained over each subaperture, a set of directive radar beams, which represents radar data as a function of range and direction, with an angular resolution determined by the subaperture length and the wavelength and associated with a given position within the subaperture, and generates a topography for the planetary surface, either based upon a topographical map or an assumption and produces an SAR image by computing radar reflectivity of all surface points forming an image by a summation of the collected signal amplitudes for all subapertures at a range and beam direction determined by a position of the radar platform and the surface point.