The federal government should spend $4.7 billion on advanced optical telescopes and other astronomical projects during the next decade, a committee of the National Academy of Sciences National Research Council recommended in May. "In the first decade of the new millennium, humanity is poised to take a giant step forward in understanding the universe and our place within it," says the committee report.
The committee's top recommendation is to proceed with the Next Generation Space Telescope (NGST), which would replace the Hubble Space Telescope in space and would cost the United States $1 billion, with other funds to come from international partners. However, unlike the Hubble, the NGST would not orbit Earth. Rather, it would orbit the Sun, about 1 million miles from Earth. Its mirror also will be much larger than the Hubble's—8 m in diameter—which will make the NGST "far more capable than the Hubble," the committee says. Indeed, the NGST will be 100 to 600 times more sensitive to light from astronomical objects than existing telescopes, according to the committee.
The telescope is planned to be sensitive to radiation from 0.6 to 10 µm, but some instruments under study could expand the upper limit to as much as 30 µm. The committee also endorsed NASA's plan to continue operating the Hubble Space Telescope through the end of the decade "to maintain the capability for critical space-based ultraviolet and optical observations."
The second-highest priority among major projects is the Giant Segmented-Mirror Telescope (GMST), which is estimated to cost $350 million. That telescope would be ground-based, with a 30-m mirror and adaptive optics to compensate for atmospheric turbulence. "Together, the NGST and GMST will trace the formation and evolution of galaxies from the end of the "dark ages" when the first stars formed until the present," the committee says.
But, the committee warned that technical challenges face the segmented-mirror telescope. "The large size of the GMST means that substantial advances in telescope design and adaptive optics will be required if it is to be built for a reasonable cost. The committee recommends that this work commence soon so that construction of the telescope can begin in the coming decade."
Still, committee members are optimistic. Joseph H. Taylor Jr., a professor of physics at Princeton University and cochairman of the committee, says that adaptive optics has made major strides in the 10 years since the last major review of astronomical instrumentation. "It makes it possible to contemplate doing things from ground-based telescopes that couldn't be done before," he says.
The committee's other endorsements include a large synoptic survey telescope, with a 6.5-m mirror that could produce a new digital map of the visible sky once each week. By looking for changes in the map over time, astronomers could pinpoint new comets, asteroids, and supernovae and could compile detailed maps of galaxies.
The Terrestrial Planet Finder, a set of four 3.5-m telescopes flying in a precise formation in space as much as 1 km apart, is also of interest. Working together, the four telescopes would try to separate the light emitted by Earth-sized planets from the light emitted by their stars. Spectrometers will analyze the light for signs of molecules such as ozone and methane, which could be evidence of life. The project "will be a significant early step in our efforts to learn more about Earth-like planets and whether they harbor life," says the committee.
The top recommendation in the area of solar astronomy is the Advanced Solar Telescope, a 4-m telescope with adaptive optics that could allow astronomers to study the Sun's magnetic fields to unravel how they function. The solar telescope would cost about $60 million. In addition, a variety of x-ray and radio telescope projects as well as a National Virtual Observatory that would combine observations of the cosmos from a variety of instruments are planned.
Justify expenditures
In its report, the committee justifies the expenditures for astronomy not only on the grounds of the scientific discoveries that they will produce, but on benefits the projects offer for the nation. For example, the committee argues that major astronomical projects foster interest in science and therefore encourage students to consider careers in science and technology. On a more practical level, the report says that astronomical projects produce advances in technology with economic or military value.
"Techniques developed by astronomers for adaptive optics are being developed to produce ophthalmic instruments that can image the retina of an eye and measure an individual's eye aberrations in unprecedented detail," which would give physicians new tools for early diagnosis of eye disease, the report says.
The report is expected to carry great weight with federal agencies and with Congress. US astronomers have developed a tradition of surveys by the National Academy of Sciences to guide spending on major projects. But for that to happen, astronomers and others will have to encourage lawmakers to follow its recommendations. Says Taylor, "We need to sell this."