sizes. In order to achieve its scientific goals, NASA must carry out its plans to devote adequate resources to the Research and Analysis program and to Mission Operations and Data Analysis. This support is crucial for analyzing and interpreting data, for understanding the implications of the data through theory, and for developing new technologies for future space missions. The funding requirements for new instrumental initiatives within a balanced space program are listed in Table 1.1.

Before deciding on its final recommendations for new equipment initiatives, the committee considered the implications of the recently discovered problems with the Hubble Space Telescope.

Significance of Large Space Observatories

The operation of the first Great Observatory, the Hubble Space Telescope (HST), began disappointingly. Initial observations revealed that a flaw in its primary mirror would prevent HST from achieving its design resolution and sensitivity without corrective action. A failure in the testing and quality control of known technology apparently caused the flaw in the mirror. Investigatory committees have been appointed to identify precisely what happened, why it happened, and how to protect future programs from other major mistakes. In Chapter 7, the committee describes its view that a strong involvement by scientists is critical to the success of space projects of all sizes.

This committee has reexamined the justification for large-scale space astronomy programs, taking into account both the failure to meet specifications in the HST program and NASA's record of successes in carrying out other complex missions at the frontiers of science and technology. As will be clear from discussions later in this chapter and in Chapter 3 and Chapter 4, the committee has concluded that in some cases only large-scale programs can answer some of the most fundamental astronomical questions. The four Great Observatories currently planned by NASA for the 1990s cover a large fraction of the electromagnetic spectrum with the sensitivity and resolution required to make progress on frontier problems in astrophysics. The Great Observatories are the HST, the Gamma Ray Observatory (GRO), the Advanced X-ray Astrophysics Facility (AXAF), and the Space Infrared Telescope Facility (SIRTF).

The Great Observatories embody the ideal of “small science” made possible by large facilities; they allow individual investigators or small groups of investigators to carry out frontier research programs. The typical number of researchers is only four per proposal for the approved HST programs. Investigators at about 200 different institutions were awarded observing time for the first year of HST operations.

Nevertheless, the committee believes that a balanced space astronomy program would put increased emphasis on more frequent and less costly missions. Modest, cost-efficient missions can respond more rapidly to changing

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