Rate determination from vector observations
Abstract
Vector observations are a common class of attitude data provided by a wide variety of attitude sensors. Attitude determination from vector observations is a wellunderstood process and numerous algorithms such as the TRIAD algorithm exist. These algorithms require measurement of the line of site (LOS) vector to reference objects and knowledge of the LOS directions in some predetermined reference frame. Once attitude is determined, it is a simple matter to synthesize vehicle rate using some form of leadlag filter, and then, use it for vehicle stabilization. Many situations arise, however, in which rate knowledge is required but knowledge of the nominal LOS directions are not available. This paper presents two methods for determining spacecraft angular rates from vector observations without a priori knowledge of the vector directions. The first approach uses an extended Kalman filter with a spacecraft dynamic model and a kinematic model representing the motion of the observed LOS vectors. The second approach uses a 'differential' TRIAD algorithm to compute the incremental direction cosine matrix, from which vehicle rate is then derived.
 Publication:

Flight Mechanics/Estimation Theory Symposium
 Pub Date:
 February 1993
 Bibcode:
 1993fmet.symp..275W
 Keywords:

 Algorithms;
 Attitude (Inclination);
 Attitude Indicators;
 Kalman Filters;
 Kinematics;
 Mathematical Models;
 Onboard Equipment;
 Satellite Attitude Control;
 Satellite Instruments;
 Spacecraft Models;
 Vector Analysis;
 Angular Velocity;
 Dynamic Models;
 Stabilization;
 Astrodynamics