S.E. Grigas, D.Ts. Litovchenko, A.A. Skorynin

In the recent years much attention has been paid to space debris problem since the number of object in Earth orbit has steadily increased. Thus the detection and tracking of orbital objects - especially the low-sized - is of great importance. Modern radar systems are used for low Earth orbit (LEO) objects tracking whereas optical telescopes are primarily used for high Earth orbits (HEO). Since radars have several advantages over optical systems there is a need for radar observations of space debris at HEO. Radar tracking of low-sized objects at HEO using ground based radars requires antennas with several tens meters diameter and 100 kW and higher radio frequency amplifiers. Size and power requirements could be reduced by using bistatic space-ground radars (SGR). Orbital objects are illuminated by ground based transmitter and the scattered radiation is measured by receiver on highly elliptical or geosynchronous orbit. Since the distance between the object and the receiver is much less than the distance between the object and the transmitter, SGRs are much more energy efficient than ground based radars. SGR efficiency could be improved by using forward scatter geometry since when the object passes between receiver and transmitter its RCS considerably increases. Because of the narrowness of the forward scattered lobe additional orbital information should be applied. Bistatic space-ground radar systems can be used together with the ground-based radars and optical telescopes. It greatly improves space objects detection system performance and allows to detect and to track small space debris less than 1 m at HEO and to determine its parameters.