The successful development of any complex control system requires a blend of good software management, an appropriate computer architecture and good software engineering. Due to the large number of controlled parts, high performance goals and required operational efficiency, the control systems for large telescopes are particularly challenging to develop and maintain.
In this paper the authors highlight some of the specific challenges that need to be met by control system developers to meet the requirements within a limited budget and schedule. They share some of the practices applied during the development of the Southern African Large Telescope (SALT) and describe specific aspects of the design that contribute to meeting these challenges. The topics discussed include: development methodology, defining the level of system integration, computer architecture, interface management, software standards, language selection, user interface design and personnel selection.
Time will reveal the full truth, but the authors believe that the significant progress achieved in commissioning SALT (now 6 months from telescope completion), can largely be attributed to the combined application of these practices and design concepts.
The modern day computing power to cost ratio has allowed flexible yet complex mathematical models to be implemented in various arenas. A current example is the Southern African Large Telescope and the Hobby-Eberly Telescope, Arecibo-type large optical telescopes, which have a moving prime focus confined to a spherical surface. The complexity of the moving tracking mechanism, a stationary self-aligning mirror and the scales of the structures involved in such telescopes have led to the requirement of more flexible telescope mount models. In this way the combination of low cost and a requirement for flexibility has led to the design of new mathematical models for telescopes of this type.
A case in point is the Southern African Large Telescope, due to the specific design and calibration requirements during the design and commissioning of the telescope, an adaptable mathematical model is required. Such a model should have multiple easily accessible entry points and flexibility of conversion paths between the various coordinate systems involved. In this paper the authors present an overview of the special requirements for the Southern African Large Telescope and the eventual design and implementation of a mathematical model to cope with these requirements. Some of the topics that will be discussed include: tracking challenges on SALT; layering of complexity of the mathematical model; software design and access to mathematical parameters; analytical and statistical tools for model design; and design consistency between coordinate conversions.