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Prerequisites far New Research Initiatives In order to be effective, the recommended new research initiatives for the coming decade must be supported by a set of Prerequisites; these are essential for the success of all the major programs but are inexpensive by comparison. Although significant support already exists for each, the Committee strongly recommends substantial aug- mentations in the following areas, in which the order of listing carries no implication of priority: A. Instrumentation and detectors, B. Theory and data analysis, C. Computational facilities, D. Laboratory astrophysics, and E. Technical support at ground-based observatories. The present chapter discusses the importance of these support ac- tivities to the major research directions of the 1980's. A. INSTRUMENTATION AND DETECTORS The Astronomy Survey Committee recommends significantly ex- panded support for instrumentation and detectors during the coming decade as the most cost-effective way to increase the ca- pabilities of both new and existing telescopes. The past decade has seen spectacular advances in detector and 123

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124 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's instrumentation technology, resulting in two-dimensional array detectors for optical, ultraviolet, and x-ray wavelengths, and large gains in sensitivity in virtually all wavelength regions. Further development of this technology on all fronts is imperative for the efficient utilization of both ground-based telescopes and space facilities. Improvements in ancillary instrumentation, such as spectrometers, interferometers, and radio-frequency local oscilla- tors, will also be important. As in the past, support for all of these activities should come from a broad base, including the National Sciences Foundation (NSF) grants program, the National Aeronautics and Space Administration's (NASA'S) Research and Analysis program, and funding provided through the National Astronomy Centers. The potential gains are enormous, and the cost is small compared with that of major new facilities. A major detector-development program also exists in the mili- tary community, especially for infrared detectors. Rapid declassi- fication of the results of military research and development in this area would be of immense value to astronomy. An efficient means of transferring such declassified technology to the astro- nomical community is urgently needed. In many instances a technological breakthrough is only the first step-one must next ensure an adequate supply of new compo- nents to the astronomical community at reasonable cost. Com- mercially available devices may not be well suited to astronomi- cal needs, which usually include maximum sensitivity together with the lowest possible background noise. Often, however, commercial devices can be modified effectively and inexpen- sively. University laboratories and private industry can contrib- ute to these developments, and such initiatives should be en- couraged. The most critical needs for new detectors and instrumentation during the 1980's are highlighted below; a more complete dis- cussion of these and other projects can be found in the Panel Reports, to be published as a Volume 2 of this survey. 1. Infrared array detectors. Infrared imaging and spectroscopy from the ground and from space would be enormously ad- vanced by the introduction of array detectors in the 1-30-~m range, which are now being developed for military purposes but which have not yet become astronomical tools. They should be reviewed for timely declassification and adaptation to infrared v astronomy.

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Prerequisites for New Research Initiatives 125 2. Charge-coupled device (CCD) array detectors for the optical, ultraviolet (uv), and x-ray regions. With nearly 100 percent quantum efficiency, high geometric stability, and relatively low readout noise, CCD arrays can be nearly perfect detectors in the optical region; for optical-astronomy applications, however, the devices should have larger area, larger pixels, lower noise, im- proved blue response, and greater adaptability for large, close- packed mosaics than at present. The wavelength coverage of such detectors can be extended to the w region by the application of high-efficiency phosphor coatings, although this should be tested further. Two-dimensional solid-state array detectors are of special value in x-ray observations, since the amount of charge created in the detector is a measure of the energy of each incident photon, so that imaging and low-resolution spectroscopy can be carried out simultaneously. Further development should pursue the goal of detecting each individual photon with an energy resolution ap- proaching the theoretical limit. 3. Millimeter- and submillimeter-wavelength radio receivers. At high radio frequencies (including those sometimes considered to lie in the far-infrared region), the greatest need is for more sen- sitive coherent detectors. Cryogenic metal-semiconductor junc- tions (Schottky barriers), InSb mixers, and superconducting junc- tions will all require further development and increased funding during the 1980's. 4. Gamma-ray detectors. Particular needs include greatly in- creased flux sensitivity over the entire range, better energy reso- lution for emission-line spectroscopy, and higher angular resolu- tion to correlate gamma-ray sources more precisely with sources observed at other wavelengths. 5. Cosmic-ray detectors. High sensitivity and resolution are needed to investigate elemental and isotopic compositions throughout the entire periodic table, particularly for heavy ele- ments, whose abundances are extremely low. Devices of very large area are needed to measure the low fluxes expected at energies in the tera-election-volt range. 6. Optical and ultraviolet instrumentation. Greatly increased efficiency in multiobject optical spectroscopy of faint objects can be achieved using multichannel spectrometers. Increased atten- tion should also be given to the use and development of highly reflective optical coatings at all wavelengths, notably in the far w region.

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26 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's B. THEORY AND DATA ANALYSIS The Astronomy Survey Committee recommends support for an expanded program of theoretical astrophysics and data analysis during the coming decade in response to the rich accumulation of data expected from both ground-based and spacecraft obser- vatories. Astronomy is a field in which new observational discoveries are often unanticipated; their interpretation and eventual under- standing require the incorporation of an ever-increasing range of physical processes and concepts into astronomy. Theoretical modeling, usually with the aid of modern computers, is neces- sary to extrapolate the results of laboratory experiments into to- tally unfamiliar astrophysical environments. Without extensive and imaginative theoretical analysis, the observational data by them- selves are often without apparent pattern or meaning. Further- more, the new facilities to be put into operation during the 1980's promise to produce data of unparalleled richness and complex- ity, necessitating ever more sophisticated theoretical interpreta- tion. The Survey Committee thus shares the view of the Panel on Theoretical and Laboratory Astrophysics that the use of these new facilities will stimulate a correspondingly increased level of theo- retical activity. Funding agencies should therefore prepare to re- spond to an increased demand for the support of theoretical as- trophysics. Theoretical astronomical research of the broadest scope has been supported primarily by the NSF Astronomy Division. Such sup- port is critical to astronomy and should be increased. A level of funding 50 percent creaser than the present level, as a fraction 0 1 C} 1 Of NSF astronomy support, is a desirable goal. implementation could be strengthened by the establishment of a program direc- tor for theoretical astrophysics, as recommended by the Panel. It is inappropriate that the NSF Astronomy Division bear the burden of supporting the basic theory needed for a balanced program in space astronomy. We recommend that NASA estab- lish a strong, broad program in theoretical astrophysics compa- rable in scope with the NSF program, as NASA has already done in the area of theoretical solar-terrestrial physics. It is important that this support include a grants program for theory designed to further NASA'S overall mission for space-sci- ence research but that is funded independently of specific in- strumental programs. Such a grants program is necessary to en

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Prerequisites for New Research Initiatives 127 courage theoretical studies that relate results of different space- science missions to each other and to the results of ground-based astronomy, as well as to incorporate them fully into the concep- tual framework of astronomy and physics. At the same time, however, NASA should adequately support the analysis and interpretation of data obtained from specific missions; since this activity naturally includes theoretical interpretation, a significant fraction of NASA support for theory should continue to be funded through channels identified with specific instrumental programs. The Committee believes that the effectiveness of the National Astronomy Centers would be enhanced by the presence of strong in-house theoretical groups. These groups should support the activities of the Center user communities and should have a number of permanent staff theorists above the critical minimum, as do the Department of Energy national laboratories for re- search in high-energy physics; it is particularly important that the newly established Space Telescope Science Institute have a strong in-house theoretical staff. Such theoretical groups should be built up carefully in order to ensure appointments of the highest quality. C. COMPUTATIONAL FACILITIES The Astronomy Survey Committee recommends that the acquisi- tion of minicomputer and enhanced-minicomputer systems by the U.S. astronomical community be substantially accelerated. About 30 such systems, to be replaced by more advanced systems at intervals of approximately 6 years, are required for data reduc- tion, image processing, and theoretical calculations during the coming decade. However, as some forefront theoretical problems will still require the largest and fastest computers available, the Committee also recommends that federal agencies take steps to provide continued access of the U.S. astronomical community to such machines. The increasing use of digital imagery in astronomy is already producing a flood of valuable data requiring the extensive use of computers for reduction and analysis. By about 1985, most ma- jor telescopes will be equipped with CCD array detectors, the Very Large Array will be in full operation in both continuum and spectral-line modes, Space Telescope will be launched to carry out a rich observational program in optical and uv astronomy, and there will be increased use of microdensitometers to generate

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128 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's digital images from photographic plates. All together, as many as a million images may be generated each year. If the scientific content of these images is to be extracted efficiently, it is im- perative that astronomers improve their capabilities for image re- duction and analysis. Advances in computer technology now make it possible to exploit the scientific opportunities afforded by new imaging technologies at modest cost. We stress that image processing is only part of the total pic- ture: the inherent complexity of astrophysical phenomena to- gether with the greatly improved ability to measure these phe- nomena require increasingly sophisticated analytical techniques for the interpretation of observations. Astronomical phenomena typi- cally involve an intricate interplay of several strongly nonlinear effects. In such situations, theoretical modeling by digital com- putation often provides the only practical approach to under- standing. The demand for computational facilities for theoretical modeling will increase in parallel with the demand for ima~e processing facilities in the 198()'s. liere again, advances in com- puter technology allow the important scientific opportunities for detailed theoretical modeling to be exploited at a modest cost. Computational capability will continue to be provided through three main sources: university computer centers, large com- puters operated by national laboratories and observatories, and dedicated minicomputers and superminicomputers. Computers at national laboratories and observatories constitute a unique and vital resource for handling some theoretical problems, and their shared use by astronomers should be encouraged and ex- panded. In recent years, however, new computer technology has brought about a dramatic shift in the capability and cost-effec- tiveness of minicomputers in comparison with the large central computers operated by university computer centers. Minicompu- ters and superminicomputers are now able to handle almost all image processing, as well as many theoretical calculations. Their cost-effectiveness compares favorably with that of the computers operated by national laboratories and observatories and often exceeds by a large margin that of many university computer centers. Furthermore, they provide the flexibility and interactive capability necessary for creative interpretation of observational data and theoretical results. (These new computational opportunities have been recognized not only in the United States but also abroad; in 1979, for example, the United Kingdom's Science and Engineering Research Council established a network of six linked

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Prerequisites for New Research Initiatives 129 minicomputers to meet the image-processing requirements of U.K. astronomers during the 1980's.) In order for these facilities to operate effectively, attention and support must also be given to the standardization and sharing of software for the most com- monly encountered calculations. The Committee believes that the acquisition by the U.S. astro- nomical community of dedicated minicomputer- and supermini- computer-based computational systems should be substantially accelerated. However, the Committee also recognizes the exis- tence of computational problems of outstanding importance to astrophysics that can be attacked only with the most powerful computers. We urge NSF and NASA to help ensure that qualified astrophysicists continue to have access to the largest and most sophisticated computing equipment available. D. LABORATORY ASTROPHYSICS The Astronomy Survey Committee recommends expanded sup- port for the laboratory measurements of atomic, molecular, and nuclear properties needed for the interpretation of nearly all as- tronomical observations. Federal agencies should furthermore co- ordinate their efforts in providing such support and should take explicit account of the need for laboratory astrophysical data in the planning of future scientific activities and missions. The accuracy with which physical conditions can be inferred from spectroscopic observations depends directly on the breadth and precision of the data available for atomic, molecular, and nuclear processes. The laboratory research that yields these data has not been funded adequately during the past decade, with increasingly damaging consequences for astronomical investiga- tions. For example, uncertainties in solar opacities have hin- dered precise predictions of solar neutrino emission, thereby throwing doubt on an important scientific test of our under- standing of stellar structure and evolution; lack of accurate mo- lecular data is an obstacle to the quantitative understanding of physical and chemical processes in interstellar clouds and pre- vents confident use of remotely sensed spectra for an under- standing of planetary atmospheres. The funding of laboratory astrophysics has suffered from an erratic pattern of support for atomic and molecular physics gen- erally. This trend has resulted in a severe decline in the num- ber of atomic and molecular physicists responding to the grow

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130 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's ing needs of astronomy. A strong stimulus is needed to attract a greater fraction of existing laboratory talent to problems re- lated to astronomy. The 1980's will see the deployment of powerful new instru- ments for astronomical spectroscopy and a resulting unprece- dented growth in the quality and variety of astronomical spec- troscopic data. An allied growth in laboratory astrophysics will be required to utilize these new data fully. Expanded support by NSF will be needed in the years ahead. We also recommend that NASA make an increased effort in its mission-planning and Research and Analysis programs to fund the laboratory measurements in basic physics and chemistry that are needed for the interpretation of astronomical observations from space. Of particular importance to NASA missions are studies of highly ionized atoms relevant to w and x-ray spectroscopy, of molecular physics relevant to infrared and radio spectroscopy, and of heavy-nuclei interaction cross sections relevant to cosmic-ray isotope and element spectros- copy. The Committee believes that NSF, NASA, and the Depa.l~ent of Energy should develop coordinated programs for the support of research in atomic, molecular, and nuclear physics, which are of interest to astronomy and to other branches of science, and should also support interdisciplinary workshops and symposia. We furthermore urge NSF to increase its efforts to encourage labora- tory astrophysics by coordinating the relevant activities in the Astronomy and Physics Divisions. Finally, we urge the National Bureau of Standards (NBS) to in- crease its support of basic studies in atomic and molecular physics and of laboratory astrophysics. These NBS programs have con- tributed importantly to many fields of pure and applied physics as well as to astronomy, and they provide an environment in which vital cross-fertilization among these fields can occur. E. TECHNICAL SUPPORT AT GROUND-BASED OBSERVATORIES The Astronomy Survey Committee recommends expanded sup- port for the technical personnel needed to ensure the develop meet, maintenance, and enhancement of modern astronomical instrumentation at ground-based observatories. The efficient progress of optical, infrared, and radio astron- omy in the coming decade is dependent on improvements in the instrumental capability and continued productivity of ground-based

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Prerequisites for New Research Initiatives observatories. Recent advances in instrumental techniques and control systems, together with those foreseeable in the near fu- ture, represent a potential for greatly increasing the capability of both large and moderate-sized telescopes. These advances, how- ever, are worthless to astronomy unless observatories have the means to develop, implement, and maintain the working instru- ments that take advantage of them. The present shortage of technical personnel who are able to assist in the development of instrumentation, as well as in its maintainance and improvement, is a major difficulty. We urge that funds be allocated to support such personnel, with the strong proviso that the award of such funds should proceed through the normal peer-review channels and that the basis of the award be the excellence of the science proposed with the instrumentation in question. Small institutions and small telescopes should not be excluded from such awards but should be supported if the scientific pro- posals have merit. The modernization of small instruments at reasonably good sites can help alleviate the pressure on large telescopes in an extremely cost-effective way, and it provides a unique resource for small-scale but highly innovative research. 131

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The Multiple-Mirror Telescope of the Smithsonian Institution and the University of Arizona. (Photo courtesy of G. McLaughlin, Lunar and Planetary Laboratory)