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Determination of the profile of atmospheric optical turbulence strength from SLODAR data

Butterley, T.; Wilson, R.W.; Sarazin, M.


T. Butterley

M. Sarazin


Slope Detection and Ranging (SLODAR) is a technique for the measurement of the vertical profile of atmospheric optical turbulence strength. Its main applications are astronomical site characterization and real-time optimization of imaging with adaptive optical correction. The turbulence profile is recovered from the cross-covariance of the slope of the optical phase aberration for a double star source, measured at the telescope with a wavefront sensor (WFS). Here, we determine the theoretical response of a SLODAR system based on a Shack–Hartmann WFS to a thin turbulent layer at a given altitude, and also as a function of the spatial power spectral index of the optical phase aberrations. Recovery of the turbulence profile via fitting of these theoretical response functions is explored. The limiting resolution in altitude of the instrument and the statistical uncertainty of the measured profiles are discussed. We examine the measurement of the total integrated turbulence strength (the seeing) from the WFS data and, by subtraction, the fractional contribution from all turbulence above the maximum altitude for direct sensing of the instrument. We take into account the effects of noise in the measurement of wavefront slopes from centroids and the form of the spatial structure function of the atmospheric optical aberrations.


Butterley, T., Wilson, R., & Sarazin, M. (2006). Determination of the profile of atmospheric optical turbulence strength from SLODAR data. Monthly Notices of the Royal Astronomical Society, 369(2), 835-845.

Journal Article Type Article
Publication Date 2006-06
Deposit Date Apr 16, 2008
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 369
Issue 2
Pages 835-845
Keywords Atmospheric effects, Instrumentation, Adaptive optics, Site testing.