All Adjunct Galilean Satellite Orbiter Concept Using a Small Nuclear Power Source

An adjunct spacecraft concept known as the Galilean Satellite Orbiter (GSO) could gather and return significant science data using a payload consisting of plasma science and other instruments in orbit around each of three Galilean satellites using many advanced technology elements. The key to the viability of this concept is the existence of a small Radioisotope Power System (RPS) (single GPHS) and a mother spacecraft that could deliver the GSO to its final orbit and act as a relay communications path back to the Earth. Thus, the GSO would be dependant at Jupiter on the proposed Jupiter Icy Moons Orbiter (JIMO) or similar spacecraft for orbit insertion, propulsion to its target, and communications while at its target. Because of this highly capable supporting vehicle, the energy requirements for daily operations of GSO could be easily met with a small RPS system, which is now being studied by NASA and DOE, joined with a secondary battery system. The science payload would consist of a plasma instrument set (magnetometer, plasma spectrometer, plasma wave detector, and high energy particle detector), a wide angle camera, and a Doppler extractor for gravity field measurements. A small RPS now under study that would have a cylindrical shape and reject its internal heat through an end of the cylinder could enable this concept. This topology lends itself to a unique configuration concept for the GSO spacecraft using a long cylinder as the heat rejection (radiator) system for the RPS. This long cylinder has another application — it creates a long thin configuration that would enable gravity gradient attitude control of the spacecraft. This architecture would place the instruments at one end of the spacecraft and the RPS at the other allowing the maximum separation between them. Another technology element used in this design would be the Low Cost Adjunct Microspacecraft (LCAM), originally intended as a free‐flying Earth orbiting inspector spacecraft. The LCAM is configured as a small circular disk containing an extensive computational and data handling capability as well as a suite of attitude control sensors. Two of these LCAM modules could be used in the configuration — one at each end. One would act as a science support platform at the nadir end and the other would support the RPS and communications system at the zenith end. Because the LCAM communications system is designed for use in Earth orbit, a high‐power X‐band system would be required for the GSO concept mission including an advanced technology phased array antenna. Because the attitude would be known instantaneously based on the knowledge of attitude sensors, the beam would be pointed in real time in the direction of its communications’ station.