multiobject and high-resolution optical spectrometers. Such a telescope would complement its Northern Hemisphere counterpart through its ability to carry out essential scientific programs for which an infrared-optimized telescope would be less suitable. The telescope should have a monolithic mirror of optical quality sufficient to take full advantage of developments in adaptive optics techniques.

The Southern Hemisphere 8-m telescope would provide U.S. astronomers with a vital window on objects that are uniquely or best observed from the Southern Hemisphere, such as the Magellanic Clouds, the galactic center, and some of the most prominent globular clusters and radio galaxies. Without national access to a Southern Hemisphere 8-m telescope, U.S. astronomers will be at a disadvantage in understanding new objects and phenomena discovered by NASA's orbiting observatories.

Construction and Support of 4-m Telescopes

At present, only a small fraction of the first-rate investigations proposed for the 4-m telescopes of the National Optical Astronomy Observatories can be granted time, and often the time available is so minimal as to preclude ideas and programs with high risk but potentially great return, or the assembly of databases adequate to ensure proper interpretation. This pressure will increase as discoveries made with 8-m telescopes and the space observatories place insuperable demands on existing facilities for supporting observations.

Examples of the range of important scientific programs requiring extensive time on 4-m-class telescopes include characterizing, through imaging and spectroscopy, the physical properties of sources discovered at nonvisible wavelengths; determining the interior structures of stars through long-term programs of spectroscopic monitoring of stellar oscillations; searching for planetary systems and subsolar mass objects by means of long-term radial velocity studies of large samples of stars; carrying out statistically complete spectroscopic and photometric studies of supernovae in galaxies and in active galactic nuclei; determining the mix of stellar populations in galaxies of a wide variety of ages and morphologies; mapping the large-scale structure of the universe out to a distance of 1 billion light-years (corresponding to redshifts of z ~ 0.1) by determining the redshifts of a million galaxies; and mapping the large-scale structure of the universe far beyond a billion light-years (corresponding to redshifts of z ~ 1) by determining redshifts of galaxies in carefully selected areas.

Fortunately, the technological advances that enable the construction of 8-m-class telescopes have also greatly reduced the expected size, weight, and cost of 4-m telescopes, while enhancing their image quality and operational efficiency. The superb image quality obtained with the New Technology Telescope of the European Southern Observatory attests to the potential of these new facilities. As a result of these advances, powerful telescopes can be built by individual universities or small consortia of institutions. The committee points out that

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