Abstract: In accordance with the invention, satellite navigation, receiver system of an exploration system for exploring for hydrocarbons in earth formations can be tested for fieldworthiness using a portable microcomputer-controlled satellite navigation simulator. From encoded inputs of local latitude, longitude, Greenwich mean time and antenna height, both array data parameters and real-time control signals are generated for simulating signals of an orbiting TRANSIT navigation satellite vis-a-vis the satellite navigation receiver system. To such system the received signals are indistinguishable from conventional TRANSIT satellite navigation signals. Result: by merely cross-checking simulator "turn-key" encoded data with the final computed fix, a technologist (who need not be a programming expert) can determine the fieldworthiness of the satellite navigation receiver system.