The primary objective of the LYMAN Mission is to provide an Observatory for the study of the waveband between 900 and 1250Å. Only one previous mission, Copernicus, has given us a glimpse into the very rich astrophysical return offered in this far-ultraviolet part of the electromagnetic spectrum. However, LYMAN will provide a sensitivity some ten thousand times greater than Copernicus.

It is the enormous richness of this part of the electromagnetic spectrum which is the prime justification of the mission. No other region offers such a density and variety of atomic, ionic and molecular absorption lines. Collectively, these represent a tool of great diagnostic power in determining physical conditions and chemical compositions of astrophysical plasmas. These plasmas may be cool, and seen in absorption against a hot continuum source, or else they may be hot and emitting in their own right. In either case, LYMAN is the ideal vehicle for their study, be they in solar system objects, near newly-forming stars, in photospheres, transition layers, or coronae of stars, in interstellar or intergalactic space, or close to the active cores of galaxies. For this reason, LYMAN will be a uniquely powerful tool for use in all branches of modern day astrophysics.