Analysis of Least-Squares Attitude Determination Routine DOAO

This document describes routine DOAOP. DOAOP computes a least-squares estimate of the three-axis attitude of a spacecraft a t a single time point, t r It requires a s input (1) a data set containing the body frame components, $. (t ) , of i = 1, . . . , n 2 2 observed unit vectors and (2) a data set of the 1 r A geocentric inertial frame components, V.(t ) , of these same unit vectors. 1 r The least-squares estimate will be generalized to a weighted least-squares one if the @. (t ) and/or ?. (t ) a r e multiplied by weighting factors before 1 r 1 r being passed to DOAOP. The main body of the document is divided into two parts: the first part discusses the basic attitude determination algorithm which is used in DOAOP; the second part discusses DOAOP itself, including the auxiliary computations and operations which have been implemented to support the basic algorithm. Appendix A of the document discusses a new, alternate algorithm for computing a least-squares estimate of spacecraft attitude and describes simulation tests which were performed recently using it,