During the last decade the United States and others have orbited a variety of comparatively small exploratory instruments intended for limited use in astronomy. These instruments have demonstrated beyond any doubt the critical advantages of the space observatory working above the earth's atmos-phere they have the capability for much increased spectral range and angular resolution.
Daniel J. McCarthy,
"Design Considerations For Replaceable Instrumentation For LST", Proc. SPIE 0054, Effective Systems Integration and Optical Design I, (1 March 1974); doi: 10.1117/12.954229; https://doi.org/10.1117/12.954229