modest orbiting experiments, is required to prepare the way for such major programs in the next century.
Astronomers will uncover new phenomena with the Great Observatories throughout much of the 1990s and into the next decade. If the past is any guide, however, the problems we solve will lead to deeper questions and new directions. We must begin now the conceptual planning and technological development for the next generation of astronomy missions to follow the Great Observatories.
One example of a next-generation space observatory is a large space telescope, a 6-m telescope that would combine the light-gathering power of a large ground-based telescope with the excellent image quality, ultraviolet capability, and low-infrared background that are achievable in space. Other possible missions with great scientific potential include a large x-ray telescope equipped with detectors capable of simultaneous imaging and spectroscopy; a submillimeter observatory consisting of a deployable 10-m telescope or an orbiting array of smaller telescopes operating as an interferometer; a single large radio telescope many kilometers across; and five orbiting radio telescopes of 100-m diameter forming an array that surrounds the earth.
The committee recommends that NASA pursue the technology initiatives listed in Table 1.3 as a prerequisite for initial definition studies of the next-generation space astronomy missions to be initiated early in the second half of the 1990s.
The panel reports in the Working Papers (NRC, 1991) contain detailed discussions of technologies that require further study. The development of advanced projects should proceed in a step-by-step manner with frequent tests of technologies and the involvement of key personnel by means of scientific missions of increasing scope. These studies would provide the basis for the selection, by the turn of the century, of a new mission to follow the Great Observatories.
The scientific imperatives and the infrastructure available at the time of selection will influence which missions are chosen. Technical issues will include the construction and control of lightweight systems, the capabilities of launch vehicles, advances in robotic construction techniques, and the availability of facilities on the moon. The technology development programs listed in Table 1.3 will provide part of the factual basis required for decisions about future astronomical missions.