Riccardo Giacconi worked at the Harvard-Smithsonian Center for Astrophysics from 1973 to 1981. During that period, he led the development of the Einstein X-ray Observatory, which was launched in 1978. The Einstein Observatory was the first fully imaging non-solar X-ray telescope put into space. It provided, for the first time, the capability to image extended objects, diffuse emission, and to detect faint sources. It was also the first NASA X-ray mission to have a Guest Observer program. In 1976, Giacconi and Harvey Tananbaum from the Smithsonian Astrophysical Observatory (SAO) submitted a proposal letter to NASA to initiate the study and design of a large X-ray telescope. This proposal led to the construction and launch of the very successful Chandra X-ray Observatory, which is operated from a control center at SAO. For his contributions to the field of X-ray astronomy, Giacconi was a co-winner of the 2002 Nobel Prize in Physics.