Real opening radar system for use on board a satellite and for maritime surveillance applications

摘要

A method of operating a real opening radar system (30) for surveillance of the Earth's surface, said real opening radar system (30) being installed in a vehicle / space platform (20) that moves in a flight direction and comprising a transceiver antenna (32), or a transmission antenna and a reception antenna, which is / are electronically orientable; the method comprising: a) transmitting, by means of the transceiver / transmission antenna (32), a series of M radar pulses towards a sector of the Earth's surface parallel to the direction of flight using an antenna beam aimed at said sector , in which M is an integer greater than two; b) for each of the M radar pulses transmitted, receive, by means of the transceiver / reception antenna (32), a corresponding echo signal during the time interval between the transmission of said radar pulse and the transmission of the next radar pulse using the same antenna beam as used to transmit the M radar pulses; c) carry out lifting scan cycles, in which each lift scan cycle is carried out by repeating N times the operations a) and b) and electronically changing, each time, the direction of elevation signaling of the antenna beam so that, in each elevation exploration cycle, radar pulses are transmitted to, and echo signals are received from, N sectors of the Earth's surface that are parallel to the direction of flight and are adjacent or partially overlaps, in which N is an integer greater than one; in which all radar pulses are transmitted: - with a predefined pulse repetition frequency and a predefined scan cycle timing in such a way to ensure complete coverage of each of the N sectors parallel to the direction of flight; and - using a frequency agility technique; in which all transmitted radar pulses have one and the same predefined bandwidth; in which the M radar pulses transmitted, in an elevation scan cycle, towards one and the same sector each occupy a respective frequency band having said predefined bandwidth and is identified by a respective reference frequency which is separated from the reference frequencies of the radar pulses transmitted immediately before and immediately after, by a first frequency jump; wherein said first frequency jump is greater than said predefined bandwidth and is less than a value that: - indicates the minimum frequency jump that causes a de-correlation of a target illuminated by two successive radar pulses having reference frequencies separated by at least said minimum frequency jump; and - it is related to a reference size of a generic target to be detected by the real aperture radar system (30); wherein the reference frequencies of the M radar pulses transmitted, in an elevation scan cycle, to one and the same sector are selected around one and the same central transmission frequency; and wherein in each elevation scan cycle a respective central transmission frequency is used for each sector, respective central transmission frequency that is separated, from the central transmission frequencies used in said elevation exploration cycle for the other sectors , for a second frequency jump that is greater than the first frequency jump.