Laser optical communication systems with space transmitters

摘要

Since 2001 Institute of Astronomy of Russian Academy of Sciences is working out space astrometric mission devoted to the basic problems of modern astronomy - establishment of inertial space co-ordinates frame and measurement of parallaxes of any bright star inside our Galaxy. To do this it was necessary to make astrometric instrument with un-precedent precision of few microseconds of arc. We managed to design such instrument, and now we are ready to move up to the Stage "B" of the project and plan the launch of the mission at 2012-2014. Designed device allows measuring directions to the astronomical sources, and it can also be used for telescope pointing to target objects in the space as well as on the Earth. If optical receiver/transmitter telescope is paced on the geostationary orbit, the laser beam from 1-meter telescope will illuminate a patch on the Earth's surface about 30 meters. To provide stable connection between space and Earth's telescopes it is necessary to have pointing accuracy for both telescopes not worse then 0,015". It is obvious that propagation of light beam through Earth's atmosphere must be very carefully pre-calculated. Besides refraction that changes beam direction, the transmitted from Earth laser beam will be widened by atmosphere turbulence. Widened to diameter 5" beam has to be 500 times more powerful then undistorted one, so study of possible ways of fine handling of the passed through atmosphere beams is valuable for creation of laser communications systems.