LASER METROLOGY SYSTEM FOR RADIO TELESCOPES

A HIGHLY PRECISE REMOTE MEASUREMENT SYSTEM FOR THE PURPOSE OF DYNAMICALLY MAINTAINING THE FIGURE OF SUBMILLIMETER-WAVE RADIO TELESCOPE REFLECTORS IS BEING DEVELOPED. SUCH STRUCTURES ARE NORMALLY DISTORTED BY THE COMBINED EFFECTS OF WIND FORCES AND DIFFERENTIAL THERMAL EXPANSION. THE RESULT OF SUCH DISTORTIONS IS THAT THE TELESCOPES ARE UNABLE TO ACHIEVE DIFFRACTION-LIMITED ANGULAR RESOLUTION. THE IMPLEMENTATION OF A SERVO SYSTEM IN SUCH TELESCOPES WOULD, AT VERY SMALL INCREMENTAL COST, IMPROVE THEIR PERFORMANCE (ANGULAR RESOLUTION) BY AS MUCH AS AN ORDER OF MAGNITUDE. SUCH A SERVO SYSTEM NEEDS ACTUATORS TO CONTROL THE FIGURE, AND A METROLOGY SYSTEM TO GENERATE THE ERROR SIGNALS WHICH DRIVE THE ACTUATORS. THIS PROJECT IS AIMED AT CREATING THE NECESSARY METROLOGY SYSTEM. IT SHOULD BE NOTED THAT MODERN SUBMILLIMETER-WAVE ANTENNAE (OR REFLECTOR DISHES) ARE ALREADY EQUIPPED WITH MECHANICAL ACTUATORS, WHICH ARE USED TO BRING THE REFLECTOR TO ITS OPTIMUM SHAPE FOLLOWING INSTALLATION. IT IS A RELATIVELY STRAIGHTFORWARD MATTER TO PROVIDE THESE ACTUATORS WITH ELECTRONIC CONTROLS TO COMPLETE THE SERVO LOOP. THE TECHNOLOGY IS APPLICABLE NOT ONLY TO FUTURE TELESCOPES AND TELESCOPES UNDER CONSTRUCTION, BUT ALSO AS A RETROFIT TO EXISTING SUBMILLIMETER-WAVE TELESCOPES, AND TO PROVIDE PRECISION METROLOGY FOR MEASURING OTHER LARGE STRUCTURES SUCH AS AIRCRAFT, SPACE STATIONS, BUILDINGS, BRIDGES, ETC.