Absorption, refraction, and scintillation measurements at 4700 Mc/s with a traveling-wave tube radiometer

Abstract By means of radio astronomy techniques, measurements of atmospheric absorption, refraction, and scintillation were made at C band (4700 Mc/s), with the sun as a source of radiofrequency energy. The equipment, a comparison-type radiometer, used traveling-wave tubes, a tuned radio frequency receiver, and an altazimuth antenna mount. The average solar temperatures recorded for the period varied from 22,000°K at zero elevation to 26,000°K at 60° of elevation. Individual readings ranged between 18,000° K and 30,000° K. The mean absorption, based on average solar temperatures at the various elevations for the period, was 0.00348 dB/km. Refractive errors were approximately the same as optical although deviations from the mean during any day were large. Atmospheric scintillation for periods ranging fom 0.5 sec to 90 sec were recorded. Scintillation amplitudes ranged from 2 per cent to 20 per cent of antenna signal temperature at low angles. At high elevation angles, scintillations rarely reached 10 per cent and were generally less than 1 per cent.