Relative navigation in autonomous spacecraft formations

Spreading of spacecraft formations and constellations made up by affordable platforms as cubesats poses the issue of technologically simple navigation subsystems, mandatory to exploit these missions. This paper describes solutions based on hardware that should be either already included or easy to accommodate on these platforms. Specifically, basic radiofrequency link's observables as the signal strength and the Doppler shift, and findings from onboard camera as a coarse positioning of the target are considered. The accuracy in the relative navigation attainable by means of simple estimation processes, easy to implement in the onboard computer, is obtained. The approach could also be used to identify inexpensive back-up solutions to more complex and accurate main navigation subsystems.