Hans J. Liebe

Abstract: Atmospheric radio wave propagation in the 40 to 140 GHz band is influenced by microwave spectra of oxygen (02-MS) and water vapor. The report treats the complementary roles of controlled laboratory experiments and computer analysis for providing detailed molecular transfer characteristics. A pressure-scanning differential refractometer was operated at fixed frequencies between 58 and 61.5 GHz. The variability of 02 and H20 spectra with frequency, pressure, temperature, and magnetic field strength was studied under conditions which occur in the atmosphere. Results obtained (a) for oxygen and air on the 9+ line, the 7+/5- and 3+/9- doublets, and the continuum spectrum and (b) for water vapor on nonresonant effects are reported. The experimental O2-Ms data are used in theoretical analyses of attenuation and d1spersion rates which are extended to other lines, to frequencies identified for remote sensing applications, and to temperature and pressure sensitivities between 40 and 140 GHz.

Keywords: atmospheric propagation; attenuation profiles; dispersion profiles; EHF transfer characteristics; oxygen microwave spectrum; water vapor microwave spectrum

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