Elevation angle determination for SuperDARN HF radar layouts

The international scientific radars known as the Super Dual Auroral Radar Network (SuperDARN) are designed to primarily measure plasma convection at ionospheric altitudes over a large region of the Northern and Southern Hemispheres. SuperDARN radars are equipped with a secondary interferometry array that is used to measure the elevation angle ( α ) of signals. These values of α have been used in relatively few studies; however, they are important for estimating ionospheric quantities and for accurate geolocation of the ionospheric source region of backscattered signals. The majority of SuperDARN radars are constructed with interferometers that are separated from their main array in one or two dimensions, and a relatively straightforward algorithm gives reasonably accurate results. A solution to the more general case, where offsets in all three dimensions are present, is desirable for future designs and necessary for at least one operational radar. Details of such an algorithm are described here and applied to phase measurements from several radars. For radars with interferometers offset only along the radar boresight and vertical directions, small differences of up to ∼1.5° in α are observed and negative values of α , which are deemed unphysical, are no longer produced. For the radar interferometer that is offset in all three dimensions the resulting values of α are consistent with expected behavior. The algorithm presented here provides a technique for accurately determining α from SuperDARN radars with offsets in all three dimensions and significantly reduces constraints placed on the positioning of interferometers for future SuperDARN radars.