The paper deals with the problem of choosing proper wavelength or a wavefront sensor involving an internal laser source and a hologram on the surface of the primary mirror of a telescope Some results of dimensional calculations for the optical arrangement for recording the hologram structure are presentech As a result a conclusion is drawn on the possibility o reducing the size of an optical stand formaking this structure by increasing the operation wavelength o the control channel of a telescopes I . INTRODUCTION Development o large orbital telescopes requires, in turn, development of primary mirror (PM ) current or real t ime measuring sys tern which is an integral part of the modern adapt ive telescope The error oC measuring and control systemmust not surpass haU o tolerance orwave front defornation on exit of telescope during its operation. The wave front sensor (WPS ) is the most important instrument of measurement system during precise correction. One or possible implementations o such a system is based on usage of a WFS with an internal laser reference source and a hologram structure (HS) on the PM sui ace I 2 Such a WPS doesn' t requires a special star orientation system and is independent of properties of object observed. The main problems of such WPS development are: uS realization, design of effective laser source, designofheterodynemodulator, chotee of optimal 0-8194-1495-6/94/$6.00 SPIE Vol. 2200/581 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/19/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx