Numerous studies have demonstrated the importance of obtaining the vertical distribution of turbulence in a time efficient way for evaluating FSO systems and related laser applications, making it necessary to specify the profile of turbulence along the atmospheric propagation path. This paper presents a method for the rapid measurement of near ground turbulence profiles. This method is capable of providing a real-time evaluation of an optical propagation link, making it a useful tool for remote sensing of atmospheric turbulence. Based on this method, a turbulence profile LiDAR has been built in Hefei (31.8°N, 117.3°E) and long-term continuous measurements of the vertical distribution of turbulence were performed from October 2021 to November 2021. The retrieved results of turbulence profiles show that the LiDAR can describe spatiotemporal distributions of turbulence intensity along the measurement path corresponding to the weather and daily time changes.
Long term observation of stellar photometer in daytime and night needs to calibrate several stars. Langley calibration observation for numerous stars is a time-consuming job and some stars’ elevation angle suitable for calibration often occurs in daytime, which is not suitable for calibration due to sky background and turbulence. In this paper, a transfer calibration method of different star was realized by the combination of Astronomical Langley observation, stellar apparent magnitude and effective temperature, which is based on the calibration constant of one reference star that would be calibrated by Langley observation. A field campaign was carried out to check the transfer calibration results against two-star method calibration observation by a stellar photometer. Experimental result shows that the transfer method described in this paper is preliminarily feasible, and the method described can be used for stellar photometer real time calibrating.
Sampling and attenuation of the laser beam to be measured is the first step for detector array target to measure temporal and spatial distribution of laser intensity. Existing sampling attenuation technology is more sensitive to the incident angle of laser beam. In practical applications, sampling angle response characteristics of laser beam can be measured experimentally, and get the coefficient to be corrected. Among them, scattering sampling method is based on scattering parameters of selected sampling material, which can effectively correct sampling angle response in theoretical or simulation stage. In this paper, focusing on angular characteristics of scattering sampling for detector array target, based on bidirectional transmission distribution function, the correlation between the scattering sampling angular characteristics and scattering distribution is derived. Experiments have proved that scattering sampling angle characteristic for detector array target can be expressed in the form of ratio of material scattering distribution function. This characteristic provides a certain guidance for design of scattering sampling angle tolerance for detector array target.
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