The Geometry of Spaceborne Synthetic Aperture Radar

TL;DR

This paper introduces a new coordinate system and mathematical framework for spaceborne synthetic aperture radar, enabling accurate image processing and analysis from orbiting platforms.

Contribution

It develops a novel coordinate system and mathematical expressions tailored for spaceborne SAR in a rotating planetary environment, improving image transformation and accuracy.

Findings

Derived expressions for azimuth FM rate and isodoppler lines.

Presented a method for transforming SAR images using the new coordinate system.

Reported measurement results of map accuracy for the processed images.

Abstract

The paper defines a new coordinate system that was developed in 1977-78 for the world's first digital synthetic aperture radar (SAR) ground processor for images from the Seasat-A satellite. The coordinate system is for the range-Doppler paradigm in the context of a spaceborne platform orbiting a rotating planet. The mathematical expressions for the azimuth FM rate, isodoppler lines, target illumination trajectories and antenna attitude determination from Doppler centroid measurements are derived. The method for transforming the SAR images from that SAR digital signal processor that used these parametric inputs is also presented. The paper concludes with a report of the measurement of the map accuracy of the resulting images.