UHF maritime scintillation measurements during SOS 1981. A quick-look report

Between 1 January and 15 April 1981, investigators at the Naval Research Laboratory participated in a comprehensive Study of Scintillation (SOS '81) in the American longitude zone using radio receivers installed aboard the US Navy Research Ship USNS Hayes (T-AGOR-16). Both UHF and L-band data were obtained using the transmission from the Atlantic FLTSATCOM and from the existing complement of NAVSTAR/GPS satellites respectively. This report describes the UHF scintillation data obtained during the Hayes expedition which covered geographic latitudes between 35 deg N and 50 deg S with considerable concentration in the Southern Hemisphere. Strong scintillation at 250 MHz was observed (> or = 20dB) in the vast majority of nocturnal periods for which the magnetic dip angle (I) was within + or - 40 deg of the magnetic dip equator. This corresponds to roughly + or - 30 deg in geomagnetic latitude. This suggests that a substantial expansion in the equatorial UHF scintillation zone should be incorporated into existing models. It is thought that this new result may be circumstantially related to the enhanced solar activity during the period of observation.