Attitude Determination for NPS Three-Axis Spacecraft Simulator

Abstract

This paper presents the attitude determination method for the Bifocal Relay Mirror Spacecraft Simulator. The simulator simulates three-axis motion of a spacecraft and has an optical system emulating a bifocal space telescope. The simulator consists of three control moment gyroscopes, rate gyros, two-axis analog sun sensor, and two inclinometers. The five-foot diameter platform is supported on a spherical air bearing to offer a low-torque environment. This paper demonstrates two attitude determination methods employing the measurements from a two-axis analog IR sensor, two inclinometers, and a triaxial gyroscope. The first method implements the conventional Kalman filter algorithm. The second method uses a nonlinear observer derived from the Lyapunov’s direct method. Analytical and experimental results are presented to validate the proposed algorithm.