Use of a moire deflectometer on a telescope for atmospheric turbulence measurements

• Published in: Optics letters 2010-05, Vol.35 (9), p.1470-1472
• Main Author: RASOULI, Saifollah
• Format: Article
• Language: English
• Subjects: Astronomy; Convection, turbulence, diffusion. Boundary layer structure and dynamics; Earth, ocean, space; Exact sciences and technology; External geophysics; Fundamental astronomy and astrophysics. Instrumentation, techniques, and astronomical observations; Historical astronomy and archaeoastronomy; and other topics in fundamental astronomy and astrophysics; instrumentation, techniques, and astronomical observations; Meteorology
• ISSN: 0146-9592; 1539-4794
• DOI: 10.1364/OL.35.001470

An instrument has been built for the study of the atmospheric turbulence by measuring the fluctuation of the angle of arrival across a telescope aperture using moiré deflectometry. A slightly divergent laser beam passes through a turbulent ground level atmosphere and enters the telescope aperture. The laser beam is recollimated behind the telescope's focal point by means of a collimator. The collimated beam passes through a moiré deflectometer. The fluctuating self-image of the first grating is formed on the second grating of the moiré deflectometer and fluctuating moiré fringes are formed. Using moiré fringe fluctuations we have calculated the fluctuations of the angle of arrival, the Fried's parameter r(0), and the atmospheric refractive index structure constant. Because of the magnifications of the telescope and moiré deflectometry, the precision of the technique can potentially be 1 order of magnitude more precise than previous methods.