Joint Cross-Range Scaling and Phase Autofocus for ISAR Imaging Based on Adaptive Phase Tracking with Application to Asteroid Imaging

In planetary radar observations, accurately scaled inverse synthetic aperture radar (ISAR) images are essential for near-Earth asteroid (NEA) shape reconstruction, rotational-state estimation, and impact risk assessment. However, conventional ISAR cross-range scaling methods typically rely on time–frequency analysis or multidimensional parameter searches, resulting in high computational complexity and limited robustness under the low signal-to-noise ratio (SNR) conditions commonly encountered in NEA observations. To address this challenge, this paper proposes a joint ISAR phase autofocus and cross-range scaling framework based on adaptive phase tracking (APT). The method employs a multi-scale Laplacian of Gaussian (LoG) detector to extract isolated scatterers and reformulates Doppler chirp-rate estimation as a recursive state estimation problem. By adaptively tracking the cross-range Doppler phase of these scatterers, the target’s effective rotation velocity is directly estimated without exhaustive parameter searches. A unified phase compensation function is then constructed to simultaneously achieve range-dependent autofocus and cross-range scaling. Simulation results based on a three-dimensional NEA model with realistic planetary radar imaging parameters demonstrate the effectiveness of the proposed method in near-Earth asteroid imaging scenarios. Experimental results from a UAV turntable setup further verify its capability for cross-range scaling and phase autofocus in a controlled near-field ISAR imaging scenario. These results show that the proposed framework achieves high estimation accuracy and robustness with reduced computational cost, making it an efficient and reliable solution for practical ISAR imaging in challenging radar environments.