A multiwavelength line-of-sight experiment for remote atmospheric sensing

Simultaneous measurements have been made on a 3.57- km line-of-sight atmospheric path using a phase quadrature technique at 10.4 GHz, plus a combination of near-infrared and 23.8-GHz transmissometers operating in oxygen and water vapor absorption bands, respectively. The latter two systems provide the separate dry and wet terms of integrated radio refractivity for use in interpretation of the 10.4-GHz phase data. Direct measurement of the statistics of the phase quadrature components of the incoherent scattered field yields several incoherent field parameters not obtained before in line-of-sight experiments. The usefulness of these parameters for atmospheric characterization is being investigated. On this short path the incoherent field is primarily at phase quadrature to the coherent field, and this component is normally distributed, implying a predominantly near-field situation. The postulated decrease of the ratio of quadrature component variances, and of their cross correlation, with spectral frequency has been verified. The agreement noted between transmissometer data and 10.4-GHz phase data in the near field transfers to agreement with 10.4-GHz amplitude data in the far field. This difference, noted in a comparison of measurement spectra, is a helpful analytical tool in the characterization of the atmospheric turbulence wave number spectrum.

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