Design considerations for the Upper Atmosphere Observatory incoherent scatter radar

A new large incoherent scatter radar system has been proposed as the principal element in a binational center for studies of the upper atmosphere. The radar has been designed to yield a sensitivity comparable to the best now available and yet provide a latitude coverage of the F region of ±13°. The radar shall comprise a 100-m diameter parabolic reflector antenna that can be tilted in the magnetic meridian plane by ±85° from the zenith. This antenna will be coupled to a UHF pulse transmitter with a peak power of 10 Mw, and will serve for both transmitting and receiving. Two auxiliary fully steerable antennas will be located northeast and northwest of the main antenna and will also receive the signals. This will enable the velocity of the ion drift to be studied, permitting measurements of neutral winds, electric fields, and fluxes of ions into or from the magnetosphere. The auxiliary antennas will form 10 coplanar pencil beams, so that these drift measurements may be made at 10 heights simultaneously. The paper describes how the above concept was developed and the work of selecting a site for the radar. By locating the main station near L = 4, and the auxiliary stations about 550 km distant, it will be possible to measure the electric fields in the F region over the range 3 ≤ L ≤ 8 to an accuracy of ±2 mv m⁻¹. Thus, the radar should be able to map the electric fields produced by substorms at auroral and subauroral latitudes. In addition, the properties of the ionosphere and many parameters of the atmosphere will be determined over the altitude range 100 to 1000 km.