Navigation techniques for microsatellites targeted to the Moon

One of the main difficulties in designing a micro satellite lunar mission deals with navigation issues. Techniques typically adopted by microsatellites in Low Earth Orbits are unsuitable, while the complex instrument set used in previous, standard seized manned or automatic missions can not be accommodated inside a microsatellite bus. The idea to make use of GPS spill-overs attracts an obvious interest. The availability of the signal is questionable, so that possible augmentation by other satellite-based navigation systems, like Glonass and the future Galileo, is certainly important. A parallel development in terms of higher sensitivity receiving techniques, as the processing of long batches of data like the software receivers do is a different and effective way to overcome the problem. On the other side, the expectedly small variations in a well known dynamic environment suggest the possibility of a non-continuous tracking, with propagation of the kinematic state via an hypothetical but realistic dynamical model. The paper presents these concepts with accompanying significant results, in order to better define the possible exploiting of the GNSS signals, by means of typical microsatellite hardware, while en route to the Moon.