Advanced pointing systems for space astronomy

It is noted that the requirements on image stability are increasing, often at the same time that instrument external disturbances are increasing. A prime example of this is the pointing of large diameter optics from the Shuttle bay. To achieve cost-effective advanced pointing systems in the face of these problems, a system approach must be followed, one that encompasses a realistic assessment of requirements, the best possible detector technology, and a broad look at space vehicles and pointing systems that are available. By way of example, a rocket instrument for making measurements of the interstellar gas that uses a standard pointing system to achieve a spectral resolution of 2 x 10 to the 5th is described. It is noted that the use of a free-flying instrument avoids the high-frequency components that degrade the instrument resolution.