A Novel 2-D Geometry Reconstruction Approach for Space Debris via Interpolation-Free Operation under Low SNR Conditions

Xi Luo,Mengyi Qin,Dong Li,Hongqing Liu,Lixin Guo

doi:10.3390/rs12122059

Abstract

Two unsolved key issues in inverse synthetic aperture radar (ISAR) imaging for non-cooperative rapidly spinning targets including high computational complexity and poor imaging performance in the case of low signal-to-noise ratio (SNR) are addressed in this work. In the strip-map imaging mode of SAR, it is well known that azimuth spatial invariant characteristics exist, and inspired by this, we propose a fast ISAR imaging approach for spinning targets. Our approach involves two steps. First, a precise analytic expression in the range-Doppler (RD) domain is produced using the principle of stationary phase (POSP). Second, a novel interpolation kernel function is designed to remove two-dimensional (2-D) spatial-variant phase errors, and the corresponding fast implementation steps that only require Fourier transform and multiplications are also presented. Finally, a well-focused ISAR image is obtained by compensating the azimuth high-order terms. Compared with current imaging methods, our approach avoids multi-dimensional search and interpolation operations and exploits the 2-D coherent integrated gain; the proposed method is of low computational cost and robustness in the low SNR condition. The effectiveness of the proposed approach is confirmed by numerically simulated experiments.

Highlights

The rapid developments of the aerospace industry raised the issue of space debris, which pose a serious threat to spacecraft or satellites in orbit, with potentially disastrous consequences [1,2,3]
It can be seen that the main energy of a single target was concentrated into one range cell, which shows that the range cell migration (RCM) was well corrected using the proposed algorithm
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Summary

Introduction

The rapid developments of the aerospace industry raised the issue of space debris, which pose a serious threat to spacecraft or satellites in orbit, with potentially disastrous consequences [1,2,3]. The trajectories of space debris are complex, and besides translational motion, they are usually characterized by rapid spinning along the main rotating axis This makes range-Doppler (RD) [7,8] and range instantaneous Doppler (RID) algorithms for ISAR imaging [9,10] unusable and, in turn, it makes it challenging to produce well-focused high-resolution ISAR imaging for the spinning target. If the 2-D spatial-variant dependent phases are not properly corrected, the final RD-based images would be blurred Another issue, arising from the spinning motion of space debris and the long imaging distance, is the strong noise, which makes the signal-to-noise ratio (SNR) of the echo signal very low and prevents a precise estimation of the motion parameters [11,17]. The overall effect is that the performance of the conventional ISAR imaging for spinning target is seriously degraded

Results

Discussion

Conclusion