ABSTRACT
This chapter analyzes National Advisory Committee for Aeronautics (NASA) record of unmanned space science flight rates from 1960-1991. It assesses the degree to which NASA shifted from programs composed of multiple missions to programs composed of only a single mission. In the late 1960s and early 1970s, NASA launched a series of four spacecraft that shared the name Orbiting Astronomical Observatory (OAO). Although some of the scientific instruments aboard each spacecraft were unique, there was a substantial degree of commonality among the spacecraft support systems, instruments, and mission objectives. Anecdotal evidence about programs such as OAO described is often used to support the argument that a qualitative difference exists between NASA's approach to space science missions and the approach to missions and flight programs in NASA's "golden age". The data presented clearly demonstrate that the character of the US space-science flight program has undergone a substantial shift toward single-mission flight programs.
