GALILEI,GALILEO FLIGHT EXPERIMENT ON THE EQUIVALENCE PRINCIPLE WITH FIELD EMISSION ELECTRIC PROPULSION

An experiment to test the equivalence of inertial to gravitational (pa ssive) mass in space offers two main advantages: a signal about a fact or of a thousand larger than on Earth and the possibility of exploitin g the absence of weight. 'Galileo Galilei' (GG) is a small satellite m ission currently under study in Italy with the financial support of AS I (Agenzia Spaziale Italiana). The mission concerns a small, low Earth satellite (similar or equal to 150 kg total mass, similar or equal to 520 km altitude) with two objectives. One is scientific, in the field of fundamental physics, and the other technological within the framew ork of spacecraft propulsion and drag compensation. The scientific goa l is to test the equivalence principle to one part in 10(16), four ord ers of magnitude better than the best ground results. The technologica l goal is a full, comprehensive test of PEEP (field emission electric propulsion) thrusters for accurate drag compensation, a technology dev eloped in Europe by the ESA (European Space Agency) which is likely to become an essential component of all space experiments which require measurement of small forces. The GG experiment is based on novel conce pts and does not require low temperatures.