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Astronomy occupies a special place in the research portfolio of this country. Understanding the stars and the cosmos is one of the oldest and noblest intellectual goals of humanity. The compelling justification for astronomy research is immediately clear and its results, in particular the beautiful images obtained in the optical and infrared, excite the imagination of the public at large, as witnessed by the wide coverage of astronomy research in the media. Starting in the first years of primary school, astronomy offers numerous opportunities to improve the scientific literacy of our population, and many astronomers are becoming actively involved in K-12 education. From planetarium shows to the use of computers in the classroom, exciting approaches are being tried. Moreover, for many undergraduates of our universities, the only contact with modern science is established through an introductory course in astronomy. The recent increase in the number of astronomers may be less a consequence of federal funding than the response by universities to student demand for these highly popular courses.
Although astronomy represents the essence of basic research, it is also intimately engaged in the applied field of instrumentation in its increasingly closer interaction with industry. Astronomy's research activities depend on the development of sophisticated sensors, and the availability of low-noise and large-format CCDs and infrared arrays has produced in the last decade a revolution in our observing power. Adaptive optics and interferometric methods promise to have the same effect in the coming years. Inversely, the demanding needs of astronomy and the efforts of brilliant instrumentalists contribute to advancing the state of the art in technologies applicable to many other scientific fields and to the commercial, medical, and defense sectors. The current trend of instrument development in a university setting offers the additional advantage of involving undergraduate and graduate students, and therefore training scientists and engineers who become familiar with essential enabling technologies. Similar comments could be made about the high-performance computing increasingly necessary for data reduction, simulation of complex phenomena like galaxy formation and supernovae explosions, and archiving.
Before the advent of radio astronomy in the 1940s, most of the great discoveries in astronomy were made with large reflecting telescopes in which the light was detected by photographic film. A new technological revolution in OIR astronomy began in the 1970s, when astronomers started to replace photographic film with electronic detectors such as CCDs, effectively increasing the light-gathering power of the telescopes by factors of 10 to 30. This revolution continues today, with major advances arising from:
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The AASC report identified the outstanding scientific opportunities in astronomy and astrophysics for the 1990s and laid out a prioritized strategy for realizing those opportunities. The AASC strategy for OIR astronomy is part of a larger strategy for research in astronomy and astrophysics that includes facilities on the ground and in space. The current revolution in our understanding of the cosmos comes largely from our new-found ability to observe the sky at every wavelength of the electromagnetic spectrum, ranging from radio to gamma rays. In this strategy, OIR astronomy plays a central role. Almost every new astronomical source, whether discovered by radio telescopes on the ground or by infrared, ultraviolet, X-ray, or gamma-ray telescopes in space, must be observed by ground-based OIR telescopes to understand its physical nature and significance.
Conversely, observations with ground-based OIR telescopes are essential for the efficient use of far more costly telescopes in space. For example, the Hubble Space Telescope (HST) has a very narrow field of view and can observe only a tiny fraction of the sky. We can realize the full benefits of the HST's superior image quality and unique ultraviolet spectroscopic capability only if we identify its targets on the basis of extensive studies with ground-based OIR telescopes. Moreover, the HST will image distant sources so faint that their spectra can be measured only by ground-based OIR telescopes of far greater aperture. The same considerations apply to other NASA programs under development, such as the NICMOS infrared instrument on HST, the Space Infrared Telescope Facility (SIRTF) and the Stratospheric Observatory for Infrared Astronomy (SOFIA) infrared telescopes, and the Advanced X-ray Astrophysics Facility (AXAF) X-ray telescope. Even ignoring the scientific discoveries enabled by OIR telescopes alone, NSF's $40 M annual expenditure to support ground-based OIR astronomy can be justified easily on the basis of the enhanced scientific yield from NASA's $800 M annual funding of space astrophysics.
The AASC report pointed out that major opportunities to address fundamental cosmic questions will be enabled by new technologies and instrumentation for ground-based OIR telescopes. For example:
The AASC report recognized that the most dramatic advances in these and other areas would probably come from observations in the infrared band, where many of these phenomena are most easily observed. Great advances in our ability to obtain infrared images and spectra are now being achieved with new large-scale array detectors with high quantum efficiency and very low noise and dark current. Moreover, the opportunity to obtain much sharper images from ground-based telescopes will be realized first at infrared bands, for which the effects of atmospheric distortion are most easily compensated. For these reasons, as well as the scientific promise of proposed NASA observatories such as SOFIA and SIRTF, the AASC report called the 1990s "the decade of the infrared."
Dramatic confirmation of the prescience of that remark comes from the impact of comet Shoemaker-Levy 9 with Jupiter. The effects are most clearly evident in infrared images taken with telescopes equipped with adaptive optics correctors and wide-format infrared array detectors that were not available five years ago. Even as this report is written, these images are appearing on the front pages of the world's newspapers, magazine covers, and television news broadcasts. This remarkable event, the likes of which may not recur for millennia, will tell us much about the nature of comets, the atmosphere of Jupiter, and the mechanisms for mass extinctions that occur on Earth on time scales of tens of millions of years.
The sky contains literally billions of sources visible to OIR telescopes, representing an amazing variety of phenomena. A partial list includes:
Even using all the telescopes available, only a tiny fraction of these sources can be observed in a human lifetime. A strategy to optimize progress in understanding such a sky will not be highly focused--it will require great diversity of facilities, observing strategies, and ideas.
The commissioning of the two powerful Gemini telescopes in 2000 and 2003 will open new opportunities for research by the U.S. astronomical community. The 8-meter Gemini North telescope on Mauna Kea was the AASC report's highest-priority recommendation for a ground-based facility. It will be optimized for diffraction-limited operation at infrared wavelengths and will be a unique facility using revolutionary infrared array detectors to make the high-spatial- and high-time-resolution observations needed to study phenomena ranging from protoplanetary disks around young nearby stars to the most distant galaxies in the early universe. The 8-meter Gemini South telescope, located in Chile (see back cover), will provide U.S. astronomers with a vital window to the Magellanic clouds, the center of the Milky Way, and other southern sky objects.
The estimated annual cost for the IGP to operate the two Gemini telescopes will be about $11 M, of which the United States is obliged to provide half. In addition, NOAO estimates an annual cost of $2.5 M to support access by the U.S. community to the Gemini telescopes, including partial support for continued instrument development, observer support, and analysis and archiving of data. The net cost, $8 M, is well within the normal guidelines for the operation of any major astronomical facility, which is about 10% per year of the construction costs.
Modern OIR astronomy involves a mix of telescope sizes and types. The largest and most expensive telescopes, such as the 8-meter Gemini telescopes (see Plate 1) and the 10- meter Keck telescopes (see Plate 2), will have unique power to record images and spectra of the faintest and most distant sources in the sky. But it would be extremely wasteful to use these great telescopes to observe systems that can be observed equally well, and often far more efficiently, by smaller telescopes. For example, these great telescopes have relatively narrow fields of view, whereas modern 2- to 4- meter-class telescopes can observe a far greater number of sources at once because they have larger fields of view. Thus, a strategy for efficient use of the large telescopes requires smaller telescopes to select the most promising targets from the myriad of sources. Moreover, there are many projects of great scientific merit, such as redshift surveys and mapping of extended sources, that can be done more efficiently with smaller telescopes.
In addition to large and moderate general-purpose telescopes, an efficient infrastructure for OIR astronomy will include telescopes designed for special purposes. Some important programs can be accomplished at great savings in telescope construction and operation by sacrificing versatility. For example, the Hobby-Eberly Telescope (HET; see Table 2) has a 10- meter fixed spherical primary mirror and a movable secondary mirror--the optical equivalent of the Arecibo radio telescope. By sacrificing pointing and steering capability, the HET can measure spectra of faint objects at a small fraction of the cost of doing so with a general-purpose telescope of comparable effective aperture (6 to 8 meters). Other very important projects, such as the Two Micron All Sky Survey (2MASS) of millions of infrared sources and the Sloan Digital Sky Survey (SDSS) to measure the colors and spectra of millions of galaxies and quasars, can be carried out only with dedicated special-purpose telescopes.
An efficient strategy for OIR astronomy will also accommodate a diversity of observing modes. Programs to develop new instrument technology will require substantial amounts of dedicated telescope time. Some observations, which push the performance limits of telescopes and instruments, can be carried out successfully only by astronomers intimately familiar with the facilities. Uniform surveys of large numbers of sources may require tens or hundreds of nights of telescope time but can be carried out according to an established routine. Some such programs may now be accomplished most efficiently by remote observing. At the other extreme, a new discovery at radio or X-ray wavelengths may require a snapshot taking only a few minutes of telescope time or, as is frequently the case, it may lead to an extensive campaign for coordinated ground- and space-based OIR observations. Much important science can be achieved most efficiently by creating a large uniform data set and analyzing the results later, as was the case with the Infrared Astronomy Satellite and will likely be so for the SDSS. These various observing modes will complement, but not replace, the traditional observing run of a few nights, which will still be needed for experienced astronomers to carry out many kinds of programs and to provide hands-on training of new astronomers.
Some observations might be done best if scheduled in a queue and executed by staff astronomers instead of the investigator, much as most observations with space observatories are carried out. Queue scheduling can be efficient because it permits (1) observations that require rare conditions such as exceptional seeing; (2) greater efficiency in executing short observations; (3) greater flexibility in ensuring that observations of highest scientific priority are executed; (4) ease of scheduling time-critical observations such as targets of opportunity and synoptic studies; and (5) optimal scheduling of observations to ensure observations at minimum air mass and correct lunar phase.
Most of the major OIR telescopes in the United States are located at independent observatories, owned and managed by state and private institutions (see Section II). This situation, in which the majority of the capital assets were provided by private and state sources, is a unique and enormous asset to U.S. physical science. Because these independent observatories operate more than two-thirds of the major U.S. telescopes and are used primarily by about half of the OIR astronomers in the United States (Section II), they can support scientific programs of great merit that are beyond the resources of the NOAO. In particular, the independent observatories can devote greater fractions of their telescope time to testing of innovative instrumentation and to extensive observing projects requiring tens or hundreds of nights of telescope time. The independent observatories also make a major contribution to the research of astronomers not affiliated with their own institutions, through informal collaborations, guest observer programs, and the data that they disseminate to the community.
NOAO adds a vital dimension to OIR astronomy (and solar astronomy) in the United States. Since KPNO began operations in 1960, NOAO has provided world-class telescopes, particularly the 4-meter telescopes at KPNO and CTIO. The CTIO has been especially important to U.S. astronomers because its facilities have provided vital access to the southern sky (the only other major U.S.-owned Southern Hemisphere telescope is the 2.5-meter Dupont telescope of the Las Campanas Observatory). NOAO enables many astronomers at universities without major telescopes to carry out frontier research on the basis of open peer-reviewed competition. NOAO also provides crucial observing options not otherwise available to astronomers at independent observatories. Likewise, NOAO provides vital access to OIR telescopes for radio and space astronomers.
The NOAO includes the National Solar Observatories (NSO), which provide the U.S. solar physics community with access to observing capabilities not available elsewhere in the United States. These include the infrared capabilities of NSO facilities on Kitt Peak and the high-angular-resolution facilities in the optical at Sacramento Peak.
Recently, NOAO has entered into a number of successful partnerships with university instrument groups and independent observatories, such as the deployment at CTIO of the OSIRIS infrared spectrometer that was developed by Ohio State University, and the construction and joint operation at KPNO of the WIYN telescope, a partnership of the University of Wisconsin, Indiana University, Yale University, and NOAO. NOAO has exerted leadership in some areas of instrumentation development. Outstanding recent examples are the Hydra multifiber spectrograph (see Plate 5) and the deployment of large-format optical and infrared detector arrays. NOAO has acted as a national resource for instrumentalists by providing advice and technical information freely. NOAO has also developed and supported standards for data archiving and analysis, including the IRAF data-reduction software that is used by astronomers worldwide.
OIR astronomy in the United States gains strength not only from the infrastructure of the independent observatories and the NOAO, but also from a growing variety of international collaborations. The State of Hawaii has the good luck to have, on Mauna Kea, the best site in the world for many kinds of OIR astronomy (see front cover); as a result, the University of Hawaii is a partner in the operations of several international telescopes, notably the 3.6-meter CFHT, the 3.8-meter United Kingdom Infrared Telescope, and the 8-meter Japanese Subaru Telescope, currently under construction. International cooperation will become a much greater part of the U.S. OIR astronomy infrastructure with the completion of the two 8- meter telescopes of the international Gemini project, a collaboration between the United States (50% share), the United Kingdom (25%), Canada (15%), Chile (5%), Brazil (2.5%), and Argentina (2.5%). In addition, a number of independent observatories have undertaken to build major OIR telescopes in partnership with other countries, notably the Large Binocular Telescope (LBT), the HET, and the SDSS (see "The Independent Observatories" in Section II).
Given the diversity of scientific challenges for OIR astronomy, it is no easy task to suggest mechanisms to optimize the productivity of the complex infrastructure that is required to meet them. Indeed, this panel cannot dictate how this infrastructure will develop or foresee the scientific and technical problems and opportunities that will arise. The best that it can do is to identify some general principles to increase the scientific yield of the enterprise, and suggest mechanisms for making ongoing decisions that are likely to lead to a more optimum infrastructure. The principles are as follows:
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