Laser Beacon Tracking for High-Accuracy Attitude Determination

Abstract

CubeSat pointing capabilities have greatly improved in the past few years, paving the way for more sophisticated science and technology demonstration missions. Advances in attitude determination have led to the development of several CubeSat-sized attitude sensors capable of achieving fine attitude knowledge,most of which utilize natural light sources as references, such as in the case of star trackers and sun sensors. However, inertial-based attitude sensors often limit ground tracking capability of the satellite due to high ephemeris uncertainty of most CubeSats. Laser beacon tracking directly measures of the satellite’s attitude relative to a ground station or target, eliminating attitude errors induced in the coordinate frame conversion process. In addition, the use of a narrow-band artificial light source allows filtering techniques to be implemented, reducing the probability of false positives. In this paper, we present the development of a low-cost CubeSat-sized laser beacon camera along with detailed simulation development and results to demonstrate the attitude sensing performance of the module. The end-to-end simulation includes a laser link radiometry model, hardware model, atmospheric scintillation model, and sky radiance model at the beacon wavelength. Simulation results show that the laser beacon camera is capable of achieving an attitude accuracy of less than 0.1 mrad with a fade probability of less than 1% during daytime under most sky conditions for a satellite above 20-deg elevation in low-Earth orbit.