Abstract
Near space is the key to integrating “sky” and “space” into the future. A synthetic aperture radar (SAR) that works in this area would initiate a technological revolution for remote sensing applications. This study mainly focused on ground moving target imaging (GMTIm) for a near-space hypersonic vehicle-borne SAR (NS-HSV-SAR) with squint angle. The range history, parameter coupling, and Doppler ambiguity of the squint-looking NS-HSV-SAR are more complicated than traditional side-looking airborne or space-borne SARs. Thus, a precise range model is presented on the basis of phase error analyses. Then, all potential distributions of echo’s azimuth spectrum are derived, and a GMTIm method is proposed on the basis of a detailed analysis of the echo characteristics. The proposed method consists of three steps. Firstly, a prior information-based pre-processing function was created to decrease the Doppler ambiguity and range migration effects. Secondly, a blur matched keystone transform was developed to correct the residual range walk migration. Thirdly, a time-saving chirp Fourier transform was investigated for azimuth focusing. Implementation considerations, including the curvilinear trajectory of the NS-HSV-SAR, multiple moving target imaging, and applicability and limitation of the method, are discussed. Finally, simulation results are presented to validate the effectiveness of the proposed method.
Highlights
A near-space hypersonic vehicle-borne synthetic aperture radar (NS-HSV-SAR), which works at the altitude between 20 and 100 km with a speed of over 5 Mach, bridges the gap between the airborne and space-borne SARs [1]
Several state-of-the-art keystone transform (KT) based methods with few restrictions on application scenes or with similar scenarios were selected for comparison experiments, including the KT based descending stage method for side-looking NS-HSV-SAR [3], KT based long time coherent integration [22], and robust Deramp-Keystone methods [23]
This paper focuses on ground moving target imaging (GMTIm) and analysis for a squint-looking NS-HSV-SAR
Summary
A near-space hypersonic vehicle-borne synthetic aperture radar (NS-HSV-SAR), which works at the altitude between 20 and 100 km with a speed of over 5 Mach, bridges the gap between the airborne and space-borne SARs [1]. The NS-HSV-SAR would initiate a technological revolution to improve the environmental perception ability of radar [2] This device is potentially useful for SAR remote sensing applications for two reasons: Firstly, this device is timely, and exhibits a quick response, and high revisiting frequency. The NS-HSV-SAR exhibits a velocity advantage that the airborne SAR cannot match, and a flexibility advantage that the space-borne SAR cannot have Because this device works in a stable climate environment and smooth airflow disturbance, it flies without constraints through orbital mechanics. This device typically works with a squint angle or curvilinear trajectory for flexible and comprehensive detection. These features enable a timely response deployment, and multiple revisers of the detecting and key areas for NS-HSV-SAR, respectively
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