Ground Photometric Measurements Inversion Methods for Space Object Characteristics Based on Non-linear Filtering: A Short Review

The ground space optical observation system considered as one of the main measurement methods to observe space object in Medium Earth Orbit (MEO), Highly Elliptical Orbit (HEO) and Geostationary Orbit (GEO) faces difficulties in forming high-solution images for objects located in GEO that only appears several light spots with limited pixels due to the impacts of observing distance, resolution ratio, and other atmospheric conditions. The light curve is the time history of an object’s observed brightness obtained from the ground-based optical observation system through light curves, right ascension, and declination of space objects. The characteristic of space objects such as position, velocity, size, shape, and material can be inverted. This paper has analyzed the principles, applications, merits, and demerits of several non-linear filtering methods in detail. Besides, the scientific description of inversion for characteristics of a non-resolved space object from ground photometric measurements and the essence of the non-linear filtering inversion method has also been clarified. A selection principle of the non-linear filtering inversion method for different space object characteristics is then proposed, and the developing direction of such inversion methods is also described in the end.