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

A system to point and track a balloon-borne telescope with a pixel field 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 and generates error signals for the Telescope Control System, having as a reference a reduced star field database. Simulated tests show that real-time control of the telescope pointing is possible, depending on the capability of the payload primary attitude control system. The system accuracy depends mainly on the CCD pixel field of view. Using standard devices (CCD/optics) a pointing error of < 1 arcmin, in both zenith 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 substantially different in scope such as infrared experiments, x-ray, and gamma-ray telescopes would not experience difficulties whenever the utilities described in this paper are applied.