New method of precise correction for atmosphere refraction in low elevation

A new method of precise star back scanning for reducing the influence of atmosphere refraction on the measurement accuracy of optoelectronic instrument is presented. Atmosphere refraction changes with the variation of atmosphere density, temperature and pressure. The atmosphere refraction calculation based on theoretical standard atmosphere differs from that of the real situation. Accurate star library is used to guide the instrument to back scan the stars close to the observed target in realtime, and the correction factor for correcting the atmosphere refraction could be achieved from fitting back scattering data. The factors influencing correct precision are analyzed, such as shafting and encoder. Field experiments in low elevation under symmetrical changed atmosphere turbulence show that the correction precision can reach 1 arc second.