Gravity Probe A (GP-A) was a NASA project conducted by the Marshall Space Flight Center (MSFC) and by the project Principal Investigator at the Astrophysical Observatory of the Smithsonian Institution (SAO). MSFC was responsible for overall management of the project and for provision of the launch vehicle and required logistics, and SAO was responsible for the hydrogen maser payload. The probe was launched successfully on June 18, 1976 into a nearly vertical trajectory to an apex of about 10,000 kilometers (or about 6,214 miles).

At the time of the project execution, and arguably until Gravity Probe B in 2004, GP-A was the most fundamental experiment undertaken by NASA. It was a measurement of the gravitational red shift of an electromagnetic signal as dictated by the equivalence principle, a fundamental premise of Einstein's theories of relativity; thus, GP-A was an investigation at the very foundation of physical theory. The final scientific results of this historic project were published in the “Physical Review Letters,” Vol. 45, pp 2081-2084, 29 Dec. 1980 (Item GA1014 in this collection).

The GP-A project was also a remarkable demonstration of a complex and demanding collaboration between diverse personnel in several NASA organizations and the scientists, engineers, and administrators at the Smithsonian Astrophysical Observatory. The detailed project documentation that has been archived, abstracted, and cataloged captures this interplay between organizations and personnel. Although GP-A was a relatively small project compared to many NASA projects, GP-A was managed in a standard NASA manner; this archive collection can be considered as a detailed illustration of NASA project management practice at the time of its performance.