SuperDARN Iceland Interferometer Calibration Measurements

Super Dual Auroral Radar Network (SuperDARN) radars are equipped with
secondary antenna arrays in order to measure the angle of arrival
or elevation angle of transmitted signals that are backscattered
from the ionosphere or the ground/sea [Shepherd, 2017]. Numerous
techniques have been developed in order to calibrate the elevation
angle measurements of particular radars [Chisham et al., 2021]. One
technique involves comparison of geolocated SuperDARN measurements
to a known scattering source; in this case, ionospheric density
irregularities produced by a high power, high frequency ground
transmitter, or so-called heater [Burrel et al., 2016]. Observations
of backscatter from heater-induced irregularities have been used
in several studies to calibrate SuperDARN radars located in
Pykkvibaer, Iceland (PYK) and in Hankasalmi, Finland (HAN)
[Yeoman et al., 2001, 2008]. We use this technique on recent
observations from a SuperDARN radar located in Iceland (ICE) of
backscatter from ionospheric irregularities generated from the
EISCAT heater located in Tromso, Norway. In addition, we show
observations from a nearly identical radar located in Oregon (CVW)
which measured backscatter from irregularities generated by
the High-frequency Active Auroral Research Program (HAARP) heater
located in Gakona, AK. In both cases, comparisons are made with
ray tracing through model ionospheres. In both cases we show
that geolocation is significantly improved for long-range (multi-hop)
measurements when using calibrated elevation angle measurements.