Patent ID: 6356815
Filing Date: 2002-03-12
Classification: B64G,G01C,G01S

Abstract:
A method of generating an attitude estimate matrix X*(tn+) for times tn+ after respective attitude measurements at successive times tnfor use in attitude control of a spacecraft, the method comprising the steps of:at successive times tn, processing star-tracker signals from at least one star tracker to form an attitude measurement matrix Y(tn); relative to a boresight of said star tracker, deriving off-boresight angles &thgr; from said star-tracker signals for stars that are detected by said star tracker; combining said off-boresight angles &thgr; with variance coefficients &agr; to thereby generate off-boresight variances rob(tn) that are functions of said off-boresight angles &thgr; and correspond to color shift errors of said star tracker; calculating a gain matrix K(tn) with a weighted measurement-noise covariance matrix R(tn) that includes said off-boresight variances rob(tn); and Kalman filtering said attitude measurement matrix Y(tn) with the aid of said gain matrix K(tn) to thereby generate said attitude estimate matrix X*(tn+).