Optical model and calibration of a sun tracker

•We present an optimal optical sun tracker model for atmospheric spectroscopy.•The problem of loss of stability of tracker pointing at the Sun has been solved.•We propose an optimal method for tracker calibration at a measurement site.•Test results demonstrate the efficiency of the proposed optimization methods.

Sun trackers are widely used to investigate scattering and absorption of solar radiation in the Earth׳s atmosphere. We present a method for optimization of the optical altazimuth sun tracker model with output radiation direction aligned with the axis of a stationary spectrometer. The method solves the problem of stability loss in tracker pointing at the Sun near the zenith. An optimal method for tracker calibration at the measurement site is proposed in the present work. A method of moving calibration is suggested for mobile applications in the presence of large temperature differences and errors in the alignment of the optical system of the tracker.