Development of a Star Classifier for Optimal Geopositioning Purposes Using a Star-Sighting Device

In environments where Global Navigation Satellite Systems are denied, a common solution to estimate one’s position on the Earth is to use stars as inertial references, as was done centuries ago by navigators using a sextant. Nowadays, sextants have been replaced by star-sighting devices, composed of inertial sensors, precise clocks, and one or more star sensors, combining the short-term precision of inertial navigation techniques and the long-term precision of celestial ones. In this context, this paper aims at developing a star classifier for geopositioning purposes, i.e., a way to discriminate stars in the sky so that an observer can choose the stars that would provide the most precise estimate of their position regarding the sighting performances of the device used (sensor definition, precision of the inertial sensor, etc.). The star classifier proposed in this paper is based on differential calculations and spherical trigonometry, and leads to closed-form expressions that are easily embeddable to evaluate the potential of a star. These closed-form expressions are then validated on an experimental setup.