A summary of propagation studies undertaken by the 1981 expedition of the USNS Hayes

Between 1 January and 15 April 1981, investigators at the Naval Research Laboratory participated in comprehensive radiowave propagation studies in the American longitude zone using radio receivers installed aboard the US Naval Research Ship USNS Hayes (T-AGOR-16). Both UHF and L-band data were obtained using the transmissions from the Atlantic FLTSATCOM and from the existing complement of NAVSTAR/GPS satellites respectively. This report primarily describes the UHF scintillation data obtained during the Hayes expedition which covered geographic latitudes between 35 degrees N and 50 degrees S with considerable concentration in the Southern hemisphere. Preliminary study of the L-band data is underway. Strong scintillation at 250 MHz was observed (> or = 20 dB) in the vast majority of nocturnal periods for which the magnetic dip angle (I) between 0 deg and + or - 40 deg. This corresponds to roughly + or - 30 deg in geomagnetic (centered dipole) latitude and about + or 1 - 23 deg dip latitude. This represents an expansion in the equatorial scintillation zone currently thought to apply to UHF scintillation and is thought to be circumstantially related to the enhanced solar activity during the period of observation.