Remote sensing of atmospheric turbulence and transverse winds from wave-front slope measurements from crossed optical paths

Abstract

In the theory of atmospheric turbulence, the strength of the spatial variations of the index of refraction n is proportional to a parameter known as the atmospheric-structure constant. The atmosphericstructure constant is denoted C(2)(n)(z) and is a function of position along the optical path z. The characteristics of the temporal variations of the index of refraction are related to both C(2)(n)(z) and to the transverse wind velocity V(z). Current optical techniques for remotely sensing C(2)(n)(z) and V(z) rely primarily on the spatial or temporal cross-correlation properties of the intensity of the optical field. In the remote-sensing technique proposed here, we exploit the correlation properties of the wave-front slope measured from two point sources to obtain profiles of C(2)(n)(z) and V(z). The two sources are arranged to give crossed optical paths. The geometry of the crossed paths and the characteristics of the wave-front slope sensor determine the achievable resolution. The signal-to-noise ratio calculationsindicate the need for multiple measurements to obtain useful estimates of the desired quantities.

Turbulent Structure Function Analysis Using Wireless Micro-Thermometer

“…The strength of optical turbulence is usually described by the refractive index structure coefficient ( 2 n C , 2/3 m  ) [16], [17]. Bufton et al [18] measured turbulence in the troposphere by thermal sensor, then reduced its weight to less than 3 kg, and operated in only two scale ranges from a temperature difference noise level of 0.004 to a maximum temperature difference of 0.676 K [19], [20]. Azout et al [21] presented in situ technique to measure the microstructure of the temperature field in atmosphere, which gained the structure function of refractive index along with atmospheric pressure, temperature, humidity, and wind speed.…”

Laser beam wander in the atmosphere: implications for optical turbulence vertical profile sensing with imaging LIDAR

“…In recent years another technique, referred to as SLODAR (SLOpe Detection And Ranging), has been developed to monitor the vertical profile of atmospheric phase distortions and to retrieve C n 2 profile [11][12][13]. In this method a Shack-Hartmann wavefront sensor is used to observe bright binary stars, and the turbulence profile is recovered from a cross-correlation of the measured wavefront slopes (the spatial cross-correlation of angle-of-arrival fluctuations at the telescope aperture).…”