A very‐long‐baseline interferometer system for geodetic applications

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Abstract
A very‐long‐baseline interferometer system was designed and built for geodetic applications. Each interferometer terminal records a 360‐kHz spectral band of noise from a compact extragalactic radio source. The center frequency of the spectral band can be selected to sample sequentially bands covering a much wider frequency range to obtain subnanosecond accuracy in group‐delay measurements. A tunnel‐diode pulse generator is used to calibrate the delays in the receiver. The necessary sets of algorithms and computer programs have been developed to analyze the data and have allowed the system to be employed to make accurate determinations of vector baselines, radio‐source positions, polar motion, and universal time.