Aperture Averaging Effects on Scintillation and the Temporal-Frequency Power Spectrum

Aperture averaging effects on the measurement of scintillation and on the temporal-frequency power spectrum have been examined in the marine boundary surface layer using a He-Ne 6328 A laser beam propagating over various path lengths and under varying turbulence conditions. Two significant results have been obtained 1 For scintillation measurements, a vanishingly small receiver can best be approximated by using an aperture of diameter Dmin Zk sup 12 . 2 The aperture averaging correction factor for an aperture diameter D Dmin decreases as the level of turbulence increases. Data have also been obtained supporting the theoretical prediction that an increase in aperture diameter reduces the high frequency power content of the temporal-frequency power spectrum.