Fluctuations in direction and amplitude of 136 MHz signals from a geostationary satellite

Results are described which illustrate the use that can be made of directional measurements on VHF signals from a geostationary satellite in the study of ionospheric irregularities. Two different types of directional fluctuation, slow and fast, have been observed, which are respectively attributed to large and small scale irregularities. The former produce random variations of refraction which, during the six months of observation, had daytime amplitudes of a few tenths of a milliradian, but were not detectable at night. The fast directional changes were always accompanied by amplitude scintillation and, being associated with ionospheric spread-F, were probably caused by irregularities in the F-region. Scale sizes of a few kilometers have been deduced for these.