Synthesizing the Antenna Aperture Using Signals From Ground-Based Radar Stations From a Space Carrier

Abstract

Today, one of the priority directions of the aerospace industry of Ukraine is the creation of effective aerospace intelligence. Remote sensing of the Earth in the optical range provides the opportunity to obtain images of the Earth's surface for use in the military sphere and the national economy. For this, various sensors are used, which, as a rule, register radiation reflected from the surface of the Earth and objects located on it. Surveying the Earth's surface from space vehicles in the radio range allows solving a wide range of tasks. At the same time, the antenna irradiates the earth's surface with a radio signal with known parameters and receives the signal reflected from the surface over a relatively large area of the carrier's trajectory. When using a side view of the earth's surface to increase the angular separation by the path range, the artificial synthesis of the antenna aperture has become widely used. Artificially synthesizing the antenna aperture is carried out at the stage of coherent or incoherent processing of the reflected signal on a certain section of the carrier's trajectory. At the same time, the parameters of the reference trajectory signal are considered to be known with accuracy to the random phase. In contrast to the classical active methods of antenna aperture synthesis, which require the availability of information about the parameters of the radiated signal, with the passive method of antenna aperture synthesis, the parameters of the received signal are determined by the type of radio radiation source and are a priori unknown. When passively synthesizing the antenna aperture based on ground radar signals, both the maximum possible size of the synthesized aperture and the conditions for determining the azimuthal direction to the source of radio radiation depend on the parameters of the signal emitted by the radar. The paper analyzes the orbit parameters of the spacecraft, which ensure the fulfillment of the condition of the unambiguity of the determination of the azimuthal direction to the source of radio radiation and determine the resolution in terms of the path range during the passive synthesis of the antenna aperture based on the signals of typical radars operating in the pulse mode. Keywords: spacecraft; source of radio emission; resolution; antenna synthesized aperture.