SAR radar system

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.