The record of achievements during the first 5 years of scientific activity aboard the Shuttle/Spacelab is remarkable. Reams of data, scores of samples, and dozens of discoveries are the fruits of exploratory investigations in these versatile facilities. Scientists will be occupied for years analyzing and interpreting the vast amount of new information gained during these forays into space and planning the follow-up studies. The Shuttle and Spacelab are demonstrably successful research facilities for disciplines as different in aims and techniques as life sciences and astronomy, materials science and Earth observations. Scientists working in these fields, as well as solar-terrestrial physics, fluid physics, and behavioral science, have found the Shuttle/ Spacelab to be a hospitable, productive environment for pioneering research.
Despite these successes, the first missions have only begun to demonstrate the science potential of the Shuttle/Spacelab. We have not yet begun to exhaust the capabilities of the instruments for doing research in space. In many cases, the first round of investigations opened our eyes to new lines of inquiry, unexpected results, and intriguing problems that require further experiments and observations.
The impressive inventory of instruments and facilities flown to date remains available for reflight and refurbishment to carry on the investigations already initiated. Promising experiments in every science discipline are being pursued, and lessons learned on previous missions are being applied in planning future missions on the Shuttle and the Space Station.
For concentrated research pro grams, NASA is developing complementary instrument groups that will fly on missions devoted to a single science discipline. The trend of future missions will be dedicated observatories and laboratories rather than multidisciplinary payloads. Series of dedicated missions already on the Shuttle schedule include the Spacelab Life Sciences laboratory, Materials Science Laboratory, International Microgravity Laboratory, Spacelab J, Space Plasma Laboratory, Atmospheric Laboratory for Applications and Science, Shuttle Radar Laboratory, Astro, and the Shuttle High Energy Astrophysics Laboratory. Each of these specialized facilities has evolved from the first generation of Shuttle/Spacelab flights. Instruments are being modified, procedures refined, and objectives focused in response to the results obtained during previous missions.
This evolution will continue into the Space Station era, when instruments originally developed for Shuttle/ Spacelab missions will be adapted for permanent operation on the manned Station or its companion platforms. Shuttle/Spacelab missions have...
 ...provided not only the opportunity for immediate science but also the testbed for instruments and research concepts to be incorporated in the Space Station several years hence.
Some Spacelab investigations will lead to more intense investigations for longer periods aboard the Space Station. Although the scientific payload complement is not yet selected, it is expected that Spacelab experiment facilities will be adapted to the Space Station or serve as models for new apparatus. The laboratory module, for example, may include materials and life science facilities first flown aboard Spacelab. The Spacelab solar and astronomical telescopes may form a core observatory that can be mounted on the Space Station or a co-orbiting platform Instruments that scan the Earth's surface and atmosphere will be combined to form the Earth Observation System (EOS), mounted on unmanned platforms in polar orbits, to make detailed observations based the results from Spacelab missions. Plasma physics instruments and the Tethered Satellite System will form the nucleus of a Solar-Terrestrial Observatory manned module and polar platform to define how the sun and space affect our environment.
Rarely is a theory confirmed or rejected by a single observation or experiment; rather, theories and models are successively refined through a course of investigations. The Shuttle and Spacelab make such a series of investigations possible through repeated reflights and evolution of the instruments or techniques. Thus, if a first flight is not as successful as hoped or if the outcome is different than expected, scientists have the opportunity to try again or reverify unusual results. This ability to build on experience and improve investigations is directly analogous to the incremental progress of science in laboratories and observatories on the ground.
With Spacelab, we are extending our knowledge in the space sciences and learning the best ways to formulate investigations. Continued Shuttle missions spanning the development of the Space Station, and even complementing the Station as it matures, will assure the nation of a vigorous space science program as we move into the next century.
Curiosity led us into space and continues to be the impetus for space science. The Shuttle and Spacelab are well suited to satisfy the urge for discovery and knowledge.