The precision and continuity of data recorded by unmanned digital magnetic observatories depend on the type of data acquisition equipment used and operating procedures employed. Three generations of observatory systems used by the U.S. Geological Survey are described. A table listing the frequency of component failures in the current observatory system has been compiled for a 54-month period of operation. The cause of component failure was generally mechanical or due to lightning. The average percentage data loss per month for 13 observatories operating a combined total of 637 months was 9%. Frequency distributions of data loss intervals show the highest frequency of occurrence to be intervals of less than 1 h. Installation of the third generation system will begin in 1988. The configuration of the third generation observatory system will eliminate most of the mechanical problems, and its components should be less susceptible to lightning. A quasi-absolute coil-proton system will be added to obtain baseline control for component variation data twice daily. Observatory data, diagnostics, and magnetic activity indices will be collected at 12-min intervals via satellite at Golden, Colorado. An improvement in the quality and continuity of data obtained with the new system is expected. ?? 1990.
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Operation of U.S. Geological Survey unmanned digital magnetic observatories