In the fall of 1957, with the launch of Sputnik I. scientists began to explore a new universe outside the Earth's atmosphere, a universe previously invisible to astronomers and beyond the reach of physicists. Scientists and the media promptly nicknamed this universe "space" and began to call the people who explored it "space scientists." In the spring of 1958, the United States created the National Aeronautics and Space Administration (NASA) and directed it to maintain US leadership in space science and technology. At the same time, the National Academy of Sciences created a Space Science Board to interest scientists in space research and to advise NASA and the other federal agencies the Academy expected to be engaged in space research. As scientists recognized the potential for major scientific discoveries in space, they began to fight for the limited opportunities to place their instruments on board NASA spacecraft. As a result of this intense competition, a quiet but equally intense struggle developed between NASA Headquarters and the Space Science Board. Each wanted to control the process to select space scientists. Inside NASA a similar struggle evolved between NASA Headquarters and the Jet Propulsion Laboratory It took NASA three hectic years to hammer out a selection process that was acceptable to the scientists, administrators, lawyers, procurement specialists, and the institutions involved. Three decades later, NASA continues to use that same basic process: the associate administrator for the NASA Office of Space Science and Applications selects the space scientists for all NASA's missions. It is not a trivial responsibility. A major space science mission, such as Viking or the Space Telescope, may involve 100 scientists, require twenty years to complete, and cost more than a billion dollars. The current associate administrator recently (1989) selected the space scientists for what may become one of the most complex and costly of all NASA's scientific missions. In January 1988, he issued an Announcement of Opportunity inviting scientists to propose investigations for an Earth Observing System (EOS) to be launched in the mid 1990s. NASA plans to operate two of these systems for the next two decades. A year later, in NASA Press Release 89-15, he announced his selections. The opening paragraph of the "fact sheet" that accompanied the press release illustrates the magnitude, complexity, and nature of the NASA process for selecting space scientists: NASA received 455 proposals in response to the Announcement of Opportunity. Each was evaluated by scientific peers including representatives from government, academia, industry and the international Earth observation community. NASA management then selected from the ones viewed as acceptable by the peer evaluators those needed to accomplish the EOS objectives. The selection breakdown is as follows: 24 instrument investigations: 6 research facility instrument investigation team leaders and 87 team members: and 28 interdisciplinary investigators (20 U.S. 8 foreign). The various teams selected comprise 551 different individuals from 168 different institutions, universities or laboratories in 32 different states and 13 different countries. Although not mentioned in the press release, it may cost over $30 billion to build and operate the two EOS platforms for two decades and to support the research of the 55 I EOS space scientists. Not only is the selection of space scientists for such a mission a formidable technical and management challenge but it commits a substantial amount of government funds to a scientific mission. In this book the author describes the origin and evolution of the NASA selection process. Where necessary, the author touches on the concurrent political and technical forces that helped shape the process.