Sparse Imaging for Spinning Space Targets With Short Time Observation

Inverse synthetic aperture radar (ISAR) imaging is an important technique for moving target identification and classification. For the space spinning targets, a long-time observation is required to estimate the spinning parameter in the conventional ISAR imaging methods. However, for the advanced multifunctional radar, which is used for multi-target surveillance, a long-time observation for only one target is the loss outweighs the gain. To decrease the observation time, we propose a novel imaging method for spinning space targets with short time observation in this paper. Firstly, we build the imaging model by using the azimuth rotation angle caused by the spinning motion rather than the translation motion to obtain the azimuth resolution. Secondly, we utilize the orthogonal coding signals with different delays to obtain enough equivalent pulses in the short observation time. Moreover, since the equivalent pulses are block-missing to avoid overlapping of the transmitting duration and the receiving duration, we transform the imaging problem to the compressed sensing (CS) problem and solve it by modifying the Smoothed L0-norm (SL0) algorithm. Finally, both the simulations and the experiments on real data are shown to demonstrate the validity of the proposed method. Since the observing time of the proposed method only needs to cover a small percentage of one spinning period, the proposed method can be used in multi-target surveillance such as satellites and space debris.