Shape estimation of space debris using single-range Doppler interferometry

Shape estimation of space debris, or the fragments of satellites and rocket bodies left on the earth’s orbit is an important task in evaluating its danger of a possible collision with operational spacecraft. A method of imaging a space debris whose size is smaller than the range resolution of the radar is proposed. It is called Single Range Doppler Interferometry (SRDI) in contrast to the conventional Doppler interferometry which reconstruct the two-dimensional image based on the high range resolution as well as the Doppler resolution. The proposed method makes use of the fact that space debris usually follow a simple spin motion around their major axis. Two-dimensional 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 which consists of isolated isotropic scattering centers, 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 which corresponding major reflections, although the size of the body could be roughly estimated. Keywords—Radar imaging, remote sensing, shape estimation, space debris.