Combined use of satellite differential Doppler and ground-based measurements for ionospheric studies

The use of satellite differential Doppler measurements to study latitudinal variations of F -region electron density is described. It is shown that the ambiguity in the total phase path length may be resolved employing either incoherent scatter radar measurements or vertical-incidence ionosonde data, together with some assumptions concerning east-west gradients at the latitude of the observing station. Sample results are given showing the location of the midlatitude trough of electron density observed at Millstone Hill through observations of the U.S. Navy Navigation Series satellites.