Combined sar monopulse and inverse monopulse weapon guidance

Abstract

A system and method that provides for all-weather precision guidance of conventional air-to-surface weapons. The system and method employs a coherent monopulse radar disposed on a launch platform and a noncoherent passive (receive only) radar disposed on the weapon. The synthetic aperture radar generates a synthetic aperture radar monopulse map of an area around the target. The radar is used designate the location of the target, and transmit a sequence of alternating sum and simultaneous azimuth and elevation difference patterns centered on the target. The weapon includes a guidance system and seeker that is responsive to guidance commands transmitted by the synthetic aperture radar. The guidance system and seeker receives reflections of the alternating sum and combined azimuth and elevation difference pattern from the target, and the sum pulse is used by the weapon to acquire and track the azimuth and elevation difference pattern null on the target to fly an optimum trajectory to the target. One method for guiding a weapon to a target comprises the following steps. A synthetic aperture radar is used to generate a SAR monopulse map of a target area and designate a target therein. The weapon is then launched toward the target. The radar is used to transmit an interleaved sum and simultaneous azimuth and elevation difference pattern guidance pulse train at the target. The reflected interleaved sum and simultaneous azimuth and elevation difference pattern is received from the target at a seeker and guidance system on the weapon. The sum pattern is used by the weapon to lock onto the converging null, and is used by the launch platform to provide closed loop tracking of the target during guidance illumination. After weapon null lock-on, steering commands are generated to cause the weapon to fly an optimum trajectory to the target.