Miniature interferometer terminals for earth surveying

Summary

A system of miniature radio interferometer terminals is proposed for the measurement of vector baselines with uncertainties ranging from the millimeter to the centimeter level for baseline lengths ranging, respectively, from a few to a few hundred kilometers. Each terminal would have no moving parts, could be packaged in a volume of less than 0.1 m³, and could operate unattended. These units would receive radio signals from low-power (<10 w) transmitters on Earth-orbiting satellites. The baselines between units could be determined virtually instantaneously and monitored continuously as long as at least four satellites were visible simultaneously. Acquisition of the satellite signals by each terminal would require about one minute, but less than a second of signal integration, and the collection of only a few kilobits of data from two receiving units would suffice to determine a baseline. Different baseline lengths, weather conditions, and desired accuracies would, in general, dictate different integration times.