Shape estimation of space debris using single-range Doppler interferometry

Shape estimation of space debris-fragments of satellites and rocket bodies left in earth's orbit-is an important task in evaluating the possibility of debris colliding with operational spacecraft. A method is proposed for imaging space debris whose size is smaller than the range resolution of the radar, It is called single range doppler interferometry (SRDI) in contrast to the conventional Doppler interferometry, which reconstructs the two-dimensional (2-D) image based on high range resolution as well as Doppler resolution, The proposed method makes use of the fact that space debris usually follows a simple spin motion around its major axis. A 2-D image of a target can be obtained by migrating the Doppler spectrogram over one spin period. The characteristics of the proposed SRDI method are examined by means of numerical simulation, For targets that consists of isolated isotropic scattering centers, a clear image can be reconstructed with a resolution of half the radar wavelength, which is equivalent to the conventional RDI (or ISAR) technique that is applicable only when the range resolution of the radar is much finer than the size of the target. The image obtained from a conductive body is dominated by strong scattering centers with corresponding major reflections, although the size of the body could be roughly estimated.