A REAL-TIME SKY TRACKING SYSTEM FOR BALLOON-BORNE EXPERIMENTS

A system to point and track a balloon-borne telescope with a pixel fie ld of view of about 1.5 arcmin and extendible to a more general use is described. The system receives star field images from a CCD camera an d generates error signals for the Telescope Control System, having as a reference a reduced star field database. Simulated tests show that r eal-time control of the telescope pointing is possible, depending on t he capability of the payload primary attitude control system. The syst em accuracy depends mainly on the CCD pixel field of view. Using stand ard devices (CCD/optics) a pointing error of < 1 arcmin, in both zenit h and azimuth, is achievable. The software architecture is designed to simplify the experiment interfaces and to make the system as much as possible hardware independent. Thus, balloon-borne telescopes substant ially different in scope such as infrared experiments, x-ray, and gamm a-ray telescopes would not experience difficulties whenever the utilit ies described in this paper are applied.