On-Line Computers for Telescope Control and Data Handling

Abstract

The use of small computers in almost every field of science and technology has been expanding rapidly for more than a decade. As applications and demand have increased, the technology has improved and prices have fallen dramatically, leading to even faster growth and more new applications. The applications are so varied and new developments are so numerous that formal up-to-date documentation is rare; new techniques usually are disseminated at conferences, by word of mouth, and in trade journal advertisements. Formal papers in the scientific journals often mention the,use of on-line computer equipment, but rarely describe it. The phenomenal speed of development of computer hardware, software, and methodology contributes to the difficulty experienced by those involved in decision­ making processes regarding data acquisition and control systems. The enormous range of possibilities offered by the programmability of the computer almost has turned the design of computer-aided control and data-acquisition systems into an art form, reflecting the personality and experience of the designer, as well as the limitations of economics and technology. The use of computers for on-line control and data acquisition adds complexity to the problem; computer functions must not only be carried out correctly but also be synchronized to operations outside the computer. Finally, the necessity that the finished system be unobtrusive, easy to operate, and even aestiletically pleasing adds to the intricacy of the design. This article is written with the hope that it will be interesting and helpful to some of the astronomers who will specify, design, and use on-line digital computing equipment for ground-based data acquisition, data reduction, and telescope control. Because only on-line applications are considered, the characteristics of small mini computing systems are emphasized.