The Advanced X-ray Astrophysics Facility was a telescope using x-rays to see the “empty” space between stars and galaxies that is actually filled with superhot gas. The AXAF was proposed to produce sharp, magnified images in x-rays that complement those made by the Hubble Space Telescope in visible light. Renamed the Chandra X-ray Observatory CXO, the telescope was launched on the space shuttle Columbia in 1999. It is known as one of the Great Observatories.

In the early development of AXAF, NASA centers competed for where the mission should be established. The Marshall Space Flight Center (MSFC) teamed with the Smithsonian Astrophysical Observatory (SAO), the Jet Propulsion Laboratory teamed with the California Institute of Technology, and the Goddard Space Flight Center (GSFC) were all considered as locations for this mission. This subseries contains proposals from these NASA centers as well as Science Working Group meetings from the early development of AXAF. Arthur F. Davidsen was a member of the first Science Working Group assigned to work on AXAF.