Autonomous orbit navigation of interplanetary spacecraft

In this paper, autonomous orbit navigation of spacecraft for deep space missions is implemented completely independent of a ground tracking system. In order to achieve this aim, the Doppler measurement due to the relative motion from a spacecraft to the Sun is used. Other measurements are the directional data from the spacecraft to the Sun measured from a Sun sensor, and directional data from the spacecraft to the Earth measured from an Earth sensor. The observability of the system with the available measurements is investigated using a linearized observability analysis. Autonomous orbit navigation is obtained by extended Kalman filtering. Results using the Doppler measurement and Sun sensor indicate that autonomous navigation can be accomplished within an accuracy of 5km in position. Adding directional data with respect to the Earth considerably improves the estimate accuracy to within 3km.