An automatic standard magnetic observatory

An automatic standard magnetic observatory (ASMO) has been built and operated with excellent results. The observatory uses a rubidium total field-intensity detector. The detector is placed at the center of two mutually perpendicular pairs of coils which control bias fields in a plane perpendicular to the mean magnetic field vector. Use of the bias fields permits a determination of the magnetic components. A preliminary calibration procedure involving reversals of the bias fields and a mechanical rotation of the coil system eliminates uncertainties in coil geometry. Measurements are automatically recorded in digital form so that the precise value of each magnetic component and all of the usual statistical analyses can be computed automatically. Tests made so far indicate that the statistical results from the new observatory are at least as accurate as those from normal observatories. Having the data in digital form simplifies subsequent analysis of the data for research purposes.