The IGY Three-Frequency Backscatter Sounder

Design criteria and operating characteristics of the IGY Fixed-Frequency Backscatter Sounder are outlined. This three-frequency (12, 18, and 30 mc) rotating-antenna pulse sounder was designed at Stanford University for oblique-incidence ionosphere studies. During the IGY a network of these sounders has been operated at thirteen stations in polar, temperate, and equatorial regions. Data reduction and publication of data summaries have been carried out at Stanford using semiautomatic punch card methods. Preliminary analysis of data has yielded new information on sporadic-E, magnetic field aligned irregularities, large-scale traveling disturbances in the F region, and the effects of ionospheric tilts on long-distance propagation.