Height resolution analysis in geosynchronous SAR

Abstract

Owing to the curved track, geosynchronous synthetic aperture radar (GEO SAR) can obtain a height resolution. An accurate expression of the height resolution is derived for GEO SAR based on the generalised ambiguity function and the Doppler history difference between two adjacent targets at different heights. It is found that the height resolution is introduced by the accelerated motion or the curved track along the height direction in GEO SAR. Then, factors influencing the height resolution are analysed. The height resolution of GEO SAR can be improved by a longer integration time, a higher orbital inclination and a larger eccentricity. Finally, simulation results show the effectiveness of the proposed expression of height resolution.Introduction: Geosynchronous synthetic aperture radar (GEO SAR) is the SAR system running on an inclined GEO orbit [1]. Owing to the curved track in the earth-fixed frame, GEO SAR can obtain a height resolution. The height resolution expression for GEO circular SAR has been derived [2]. However, the above expression is only suitable for a circular or near-circular track with specific orbital parameters, and cannot be applied in the general case. To solve this problem, the Doppler history difference between two adjacent targets at different heights is first investigated. Then, an accurate expression of the height resolution is derived for GEO SAR based on the generalised ambiguity function (GAF) and the Doppler history difference. Contributions of different satellite track components to the height resolution are analysed. After that, factors influencing the height resolution are discussed. Finally, imaging simulations of point targets verify the derived expression.

Design of validation experiment for analysing impacts of background ionosphere on geosynchronous SAR using GPS signals

“…Currently, most researches [3][4][5] in GEO SAR are focused on the system design and performance analysis, imaging formation and applications. However, the ionosphere has significant influence on spaceborne SAR.…”