Angle-of-arrival anemometry by means of a large-aperture Schmidt-Cassegrain telescope equipped with a CCD camera

Abstract

The frequency spectrum of angle-of-arrival (AOA) fluctuations of optical waves propagating through atmospheric turbulence carries information of wind speed transverse to the propagation path. We present the retrievals of the transverse wind speed, upsilon b, from the AOA spectra measured with a Schmidt-Cassegrain telescope equipped with a CCD camera by estimating the "knee frequency," the intersection of two power laws of the AOA spectrum. The rms difference between 30 s estimates of upsilon b retrieved from the measured AOA spectra and 30s averages of the transverse horizontal wind speed measured with an ultrasonic anemometer was 11 cm s(-1) for a 1 h period, during which the transverse horizontal wind speed varied between 0 and 80 cm s(-1). Potential and limitations of angle-of-arrival anemometry are discussed.