Method for estimating the precise orientation of a satellite-borne

Abstract

The precise three-axis attitude of a space-borne phases-array antenna is estimated based on the assumption that the array geometry, consisting of the number of radiating elements and their relative spacing in three dimensions, is known and that the array position and coarse knowledge of the array attitude are available a priori. An estimate is first made of the set of complex-valued gains that define each element's straight-through contribution to the signals received at each of two or more remote calibration sites, where a 'straight-through' antenna configuration is defined as the condition in which all elements are made to radiate with the same amplitude and phase. An optimization strategy is then used to determine which array attitude lying in the neighborhood of the coarsely known attitude is most consistent with the full set of straight-through gain values. Another technique for estimating the precise angular location of a receiver with respect to the coordinates of the space-borne phased-array antenna is based on the assumptions that the array geometry is known, and that the receiver bearing is coarsely known or available. After an estimate is made of the set of complex-valued gains that define each element's straight-through contribution to a composite signal measured at the receiver site, an optimization strategy is used to determine which receiver direction lying in the neighborhood of the coarsely known direction is most consistent with the latter set of straight-through gain values.