Abstract

Because of the opacity of the atmosphere, x-ray astronomy must be conducted from space. Twenty-five years ago, the first detections of nonsolar x rays were made with simple proportional counters from sounding rockets. Collimated counters aboard rockets and satellites were used to follow up these discoveries, and more recently true x-ray telescopes have been used for the study of x rays from the cosmos. There are now thousands of cataloged x-ray sources ranging from nearby stars to distant quasars. The primary advantages afforded by telescopes for x-ray astronomy are twofold: direct imagery allows finer angular resolution than otherwise possible, and it also betters the sensitivity of the x-ray detectors via the minimization of nonsource background. The primary disadvantages are associated with the necessary grazing-incidence geometry: the effective focal length is limited by the actual telescope length, and the short-wavelength response is, therefore, sharply limited by the shallowness of the grazing angle. Examples are presented of important astronomical results that have been obtained from x-ray telescopes in space. Also presented are conceptual designs (and prototypical test results) from three different types of next-generation telescope for x-ray astronomy.

© 1987 Optical Society of America