Abstract
Compared with low-Earth orbit synthetic aperture radar (SAR), a geosynchronous (GEO) SAR can have a shorter revisit period and vaster coverage. However, relative motion between this SAR and targets is more complicated, which makes range cell migration (RCM) spatially variant along both range and azimuth. As a result, efficient and precise imaging becomes difficult. This paper analyzes and models spatial variance for GEO SAR in the time and frequency domains. A novel algorithm for GEO SAR imaging with a resolution of 2 m in both the ground cross-range and range directions is proposed, which is composed of five steps. The first is to eliminate linear azimuth variance through the first azimuth time scaling. The second is to achieve RCM correction and range compression. The third is to correct residual azimuth variance by the second azimuth time-frequency scaling. The fourth and final steps are to accomplish azimuth focusing and correct geometric distortion. The most important innovation of this algorithm is implementation of the time-frequency scaling to correct high-order azimuth variance. As demonstrated by simulation results, this algorithm can accomplish GEO SAR imaging with good and uniform imaging quality over the entire swath.
Highlights
Geosynchronous synthetic aperture radar (GEO SAR) operates at an altitude ~36,000 km [1].Compared with a low-Earth orbit (LEO) SAR, greater coverage can be achieved by GEO SAR because of its much higher orbit [2]
The goal of this paper is to develop an algorithm that can correct high-order spatial variance of range cell migration (RCM) along the range and azimuth directions, and perform GEO SAR imaging with a resolution of 2 m in both the ground cross-range and range directions
This work models the spatial variance in the time and frequency domains based on a fifth-order polynomial slant range model
Summary
Geosynchronous synthetic aperture radar (GEO SAR) operates at an altitude ~36,000 km [1]. Compared with a low-Earth orbit (LEO) SAR, greater coverage can be achieved by GEO SAR because of its much higher orbit [2]. GEO SAR can guarantee observation of the same location every 24 h with the same incidence angle, which cannot be realized by LEO SAR [3]. GEO SAR has attracted much attention [4]. It has become part of a global earthquake satellite system to monitor the global seismic state, as proposed by NASA and JPL in 2003 [5].
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