Government of the United States of America, As Represented by the Secretary of Commerce

Forskningscenter Ris.o Slashed.

Steen G Hanson

James H Churnside

Steven F Clifford

Method and apparatus for determining the rate of angular rotation of a

The disclosed invention is a measurement device for use in determining wind turbulence in the atmosphere, such as the cross-wind velocity and strength of refractive turbulence in a localized region. In the preferred embodiment, the device is comprised of: a telescope for collimating the light received from the light source, the telescope placed in front of a pair of spatially filtered optical receivers and focussed at infinity; a pair of gratings; a collecting lens, placed behind the gratings to collect the spatially filtered light; a photodetector to collect the light; an amplifier to amplify the signal received from the photodetector, and; a spectrum analyzer to analyze the interference pattern created by the gratings. The device uses the information contained in the light as it is scattered into its various Fourier components as the light passes through the atmosphere. This information, by means of the two filters, is processed to determine the turbulence, whose wavenumber is the difference of the spatial filter wavenumber of the first and the second spatial filters.

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Fakse, Denmark

Steen G Hanson