Restoration of turbulence profile from scintillation indices

Abstract

An algorithm that permits one to measure atmospheric turbulence by statistical analysis of light flux fluctuations in four concentric‐ring apertures is described in detail. It consists of computing the scintillation indices for each aperture and pairwise aperture combination and in fitting the set of measured indices to a model with a small number of turbulent layers. The performance of this method is analysed by means of simulations and using the real data from a multi‐aperture scintillation sensor. It is shown that a turbulence profile with a vertical resolution of Δh/h∼ 0.5 can be reconstructed and that the errors of the measured intensities of turbulent layers are typically around 10 per cent of the integrated intensity. The integral parameters such as the seeing and the isoplanatic angle are measured with few per cent accuracy.

Study on the precision of the multiaperture scintillation sensor turbulence profiler (MASS) employed in the site testing campaign for the Thirty Meter Telescope

“…These parameters are the instrument magnification, which is required for obtaining the projected size of the MASS apertures in the telescope entrance pupil; the Poisson parameter of each PMT channel ðP A;B;C;D Þ, which is a quantitative measure of the deviation of the photocounting device from Poisson statistics and should be close to 1; and, finally, the nonlinearity parameter for each PMT (nL A;B;C;D ), which gives the detector dead time. An in-depth discussion of these parameters is given in [5].…”

“…For the development and planning of astronomical instrumentation in general, and in particular of adaptive optics, as well as supporting operations of the existing observing facilities, devices measuring the vertical turbulence distribution-the turbulence profiles-are needed. Several instruments have been developed to measure the turbulence profiles, for example SCIDAR [1,2], SLODAR [3], or the multiaperture scintillation sensor (MASS) [4,5].…”

“…From this, MASS computes the differential scintillation indices among circular apertures of different sizes, which then allows the reconstruction of the turbulence profile [5].…”

First on-sky results of the CO-SLIDAR C^2_n profiler

“…Other methods use correlations of scintillation. Among them SCIDAR (SCIntillation Detection And Ranging) [7], which works on a double star, and MASS (Multiple Aperture Scintillation Sensor) [8], which uses a single star but only measures six turbulent layers. These techniques work better at high altitude and do not allow the estimation of near-ground turbulence, because they employ scintillation, whose variance is proportional to the altitude raised to the power 5/6 th .…”

Retrieval of Cn2 profile from differential column image motion lidar using the regularization method

“…Several approaches have been proposed to measure the C 2 n profile. The commonly used methods are the radiosonde balloon method [7] , SCIDAR (scintillation detection and ranging) [8] , SLODAR (slope detection and ranging) [9] , MASS (multiple aperture scintillation sensor) [10] , and lidar methods including differential image motion (DIM) [11] and differential column image motion (DCIM) [12,13] . Compared with other methods, lidar can measure the turbulence profile in different paths (i.e., horizontal path and slant path) based on active light detection, which makes it enjoy better application prospects.…”