Component-Aware Micromotion Parameters Estimation of Space Targets Based on Geometry Guided Time-Frequency Under Terahertz Band

Micro-Doppler (m-D) signatures serve as an indispensable component of modern space situational awareness, which provides additional feature dimension for target detection and recognition. However, the existing microwave radar systems exhibit a limited sensitivity to micromotion detection capabilities, especially in component-level motion of space targets. To address this issue, a geometry-guided time-frequency-based method is proposed to estimate micromotion parameters of space targets under terahertz (THz) band, leveraging the high frequency and inherent sensitivity of the THz band to m-D effects. First, the orbital dynamics and observation geometry tailored for spaceborne THz radar are analyzed. Subsequently, the m-D parameter estimation suitable for space targets is developed based on the geometry-guided time-frequency feature, which is different for the traditional assumption of point targets and accommodates the geometric symmetry of space targets. Finally, we compare three representative satellite attitudes with solar panels being different, i.e., nadir-pointing orientation, tilted orientation, and different direction tilted orientation, and the coat material being smooth and nonsmooth. Both numerical simulation and measured experiments are carried out to validate the effectiveness and superiority of the proposed method in terms of the reliable retrieval of m-D parameters.