M.I.T. Lincoln Laboratory is supporting the Electronic Systems Division (ESD) of the Air Force Systems Command (AFSC) in the development of the Ground-based Electro-Optical Deep Space Surveillance (GEODSS) system. As part of this program, an Experimental Test Site (ETS) has been established in the White Sands Missile Range, New Mexico, to serve as a test-bed for the system. After a brief description of the GEODSS network, the ETS and its role are defined and illustrated. Next, the matter of sensor selection for the ETS is discussed. This is followed by the consideration of the general problem of point-source detection. Experimental data are discussed which indicate the point-source response of the ETS sensors. Then, a semi-empirical model for the point-source detection capabilities of these background-limited sensors is presented. Short dicussions of the satellite population and the peculiar problems associated with the passive detection of space objects by reflected sunlight are followed by conclusions based upon brightness measurements made at the ETS during approximately two years of operation.