Measurements of Atmospheric Attenuation on an Earth Space Path at 230 GHz using a Sun Tracker

Measurements of attenuation at 230 GHz through the total atmosphere due to the presence of oxygen and water vapour molecules, clouds and rain are presented and discussed. The measurements were carried out using a specially designed superhetrodyne receiver mounted on a sun tracker. Simultaneous measurements were also carried out at 13 GHz. For a measuring site close to sea level the "clear-sky" zenith attenuation was found to be given by A(dB)=0.35+0.95W, where W is the precipitable water in cms. When the ground temperature was below about 7°C most cloud and overcast gave ¿ 0.5 dB attenuation whereas with a ground temperature greater than 13°C cloud attenuation was 8 to 10 times greater.