waves on the solar surface. These measurements established the extent of the solar convective zone and the dependence of rotation speed on depth in the sun.

  • Experiments done with solar neutrinos hinted at new physics not included in standard textbooks.

  • The mass and radius of Pluto were determined from observations of its satellite, Charon. Other studies of Pluto revealed the surprising fact that this small, cold planet has an atmosphere.

  • Deuterium was discovered in the Martian atmosphere, and this isotope was used to measure the loss of water from Mars in the past.

The 1990s: The Decade of Discovery

The 1990s promise to be a decade of discovery. The first 10-m telescope, the Keck telescope in Hawaii, will come into operation early in the decade. This telescope and the others to follow will be the first very large optical and infrared telescopes constructed in this country since the epoch-making installation of the Hale 5-m telescope on Palomar Mountain over 40 years ago. The technological revolution in detectors at infrared wavelengths will increase the power of telescopes by factors of thousands. New radio telescopes will reveal previously invisible details at millimeter and submillimeter wavelengths. A technique called interferometry will combine optical or infrared light from different telescopes separated by hundreds of meters to make images thousands of times sharper than can be achieved with a single telescope. The four Great Observatories of the National Aeronautics and Space Administration (NASA) will view the cosmos across the infrared, visible, x-ray, ultraviolet, and gamma-ray portions of the electromagnetic spectrum. These instruments, orbiting above the earth's distorting atmosphere, will answer critical questions and may reveal objects not yet imagined.

PURPOSE AND SCOPE OF THIS STUDY

Charge to the Committee

The charge to the committee was as follows:

The committee will survey the field of space- and ground-based astronomy and astrophysics, recommending priorities for the most important new initiatives of the decade 1990–2000. The principal goal of the study will be an assessment of proposed activities in astronomy and astrophysics and the preparation of a concise report addressed to the agencies supporting the field, the Congressional committees with jurisdiction over these agencies, and the scientific community. The study will restrict its scope to experimental and theoretical aspects of subfields involving remote observation from the earth and earth orbit, and analysis of astronomical objects; earth and planetary



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