The attitude of spacecraft is represented by a 3x3 orthogonal matrix with unity determinant, which belongs to the three-dimensional special orthogonal group SO(3). The fact that all three-parameter representations of SO(3) are singular or discontinuous for certain attitudes has led to the use of higher-dimensional nonsingular parameterizations, especially the four-component quaternion. In attit...

A filter for estimating spacecraft attitude quaternion and gyro drift from vector measurements in the presence of white noises in the gyro error, in the drift dynamics, and in the line-of-sight measurement error is developed. The variance parameters of the white noises are unknown, and are modeled as non-anticipative second order stochastic processes. The approach taken in this work consists in...

This paper considers a robust strong tracking nonlinear filtering problem in the case there are model uncertainties including the model mismatch, unknown disturbance and status mutation in the spacecraft attitude estimation system with quaternion constraint. Two multiple fading factor matrices are employed to regulate the prediction error covariance matrix, which guarantees its symmetry. The sp...

The well-known Wahba Problem [1] is a non-linear, weighted least-squares problem that seeks to obtain the optimal attitude matrix from a set of at least two independent vector measurements. The most common technique used to solved the Wahba problem is the so-called q-method, developed by Davenport and documented in [2]. The q-method rearranges the Wahba performance index into a quadratic perfor...

This work investigates the performances of several State-Dependent Riccati Equation algorithms for the estimation and control of attitude and attitude rates of a rigid-body spacecraft. The estimators are designed to process line-of-sight and gyros measurements corrupted by white noises and potentially drifting biases. The case of gyroless estimation is also addressed. The vector measurements ar...

Introduction Star trackers are increasingly used on modern day spacecraft. With the rapid advancement of imaging hardware and high-speed computer processors, current trackers are small and routinely achieve arc-second attitude accuracy. Typical sampling rates for these trackers range from 1 to 10 Hz. As computer processor technology advances these frequencies will increase, leading to filter de...

Attitude determination systems that use inexpensive sensors and are based on computationally e cient and robust algorithms are indispensable for realtime vehicle navigation, guidance and control applications. This paper describes an attitude determination system that is based on two vector measurements of non-zero, non-colinear vectors. The algorithm is based on a quaternion formulation of Wahb...