Importance

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Abstract

An improved local vertical reference determination technique for use with projectile guidance systems. The vertical reference determination apparatus uses a passive retroreflector mounted on the projectile to direct a portion of the incident electromagnetic radiation produced by a launching device transceiver as a return signal back to the launching device transceiver. A preferred embodiment of the invention employs a retroreflector having an axis canted with respect to the central axis of the projectile, such that the return signal is a function of the instantaneous angle of rotation of the projectile. The return signal therefore has a minimum magnitude at a first instantaneous angle of rotation and a maximum magnitude at a second instantaneous angle of rotation. The retroreflector is mounted on the projectile such that the return signal is at either the minimum magnitude or the maximum magnitude when the vertical axis of the projectile is aligned with the local vertical reference of the projectile guidance system. An alternate embodiment employs a retroreflector having a single facet. Another alternate embodiment uses a multifaceted retroreflector having at least two facets, where a first facet has a first coefficient of reflectivity and a second facet has a second coefficient of reflectivity substantially different from the first. The single-facet and multifaceted retroreflectors produce return signals having magnitudes strongly dependent upon the instantaneous angular position of the projectile.

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First Claim