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Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee (1982)

Chapter: 2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S

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Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
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Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
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Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
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Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
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Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 17
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 18
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 19
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 20
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
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Page 21
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 22
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 23
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 24
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 25
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 26
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 27
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 28
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 29
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 30
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 31
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 32
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 33
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 34
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
×
Page 35
Suggested Citation:"2 RECOMMENDED PRIORITIES FOR ASTRONOMY AND ASTROPHYSICS IN THE 1980S." National Research Council. 1982. Astronomy and Astrophysics for the 1980's, Volume 1: Report of the Astronomy Survey Committee. Washington, DC: The National Academies Press. doi: 10.17226/549.
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Page 36

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Recommended Priorities for Astronomy and Astrophysics in the ~ 980's The Astronomy Survey Committee takes note at the outset of the support provided to U.S. astronomy and astrophysics over the past decades through the scientific programs of the National Science Foundation (NSF), the National Aeronautics and Space Administra- tion (NASA), and other federal agencies. This support has enabled U.S. astronomical research to maintain an overall position of world leadership and has vastly widened our horizons for exploration of the Universe. The programs recommended in this report have been selected from research activities that were, at the beginning of the Survey, can- didates for implementation in fiscal year 1983 and beyond. Before presenting a summary of its recommendations, however, the Com- mittee wishes to emphasize the importance of approved, continuing, and previously recommended programs to the progress of astronom- ical research during the remainder of the decade. The present Com- mittee's recommendations take explicit account of such programs and build upon them. The Committee calls particular attention to the need for support of the following approved and continuing programs, for which the order of listing carries no implication of priority: Space Telescope and the associated Space Telescope Science Institute; second-gen- eration Space Telescope instrumentation; the Gamma Ray Observ- atory; NASA level-of-effort observational programs, including research with helloing aircraft. and sounding rockets, together with the Ex 13

4 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's plorer and Spacelab programs; the Solar Optical Telescope and the Shuttle Infrared Telescope Facility for Spacelab; facilities for the de- tection of neutrinos from the solar interior; federal grants in support of basic astronomical research at U.S. universities; and programs at the National Astronomy Centers. The 25-Meter Millimeter-Wave Ra- dio Telescope, which was recommended in an earlier form in the Greenstein report, has not yet been implemented. The present status of these approved, continuing, and previously recommended pro- grams is described later in this chapter; their importance for the health of U.S. astronomy in the 1980's is discussed in Chapter 4. SUMMARY OF THE RECOMMENDED PROGRAM The Astronomy Survey Committee recommendations for a pro- gram in astronomy and astrophysics for the 1980's fall into three general categories: Prerequisites for never research initiatives; New programs; and Programs for study and development. As noted in the Preface, the observational components of these recommendations are restricted to remote sensing from the Earth or its vicinity. A background and overview of the recommenda- tions follows later in this chapter. Prerequisites for 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 that apply to both the gathering and the analysis of the data pro- duced. These Prerequisites are essential for the success of major programs but are inexpensive by comparison. Although significant support already exists for each, the Committee strongly recommends substantial augmentations in the following areas, in which the order of listing carries no implication of priority: A. Instrumentation and defectors, to utilize the latest technology to enhance the efficiency of both new and existing telescopes in the most cost-effective manner; B. Theory and data analysis, to facilitate the rapid analysis and under- standing of observational data;

Recommended Priorities 15 C. Computational facilities, to promote data reduction, image pro- cessing, and theoretical calculations; D. Laboratory astrophysics, to furnish the atomic, molecular, and nuclear data essential to the interpretation of nearly all astronomical observations; and E. Technical support at ground-based observatories, to ensure that mod- ern astronomical instrumentation is maintained in the best condition permitted by the state of the art. A detailed consideration and justification of these Research Prereq- uisites appears in Chapter 5. New Programs The Astronomy Survey Committee recommends the approval and funding of new programs in astronomy and astrophysics for the 1980's. These have been arranged into three categories according to the scale of resources required. A. Major New Programs The Committee believes that four major programs are critically important for the rapid and effective progress of astronomical research in the 1980's and is unanimous in recom- mending the following order of priority: 1. An Advanced X-Ray Astrophysics Facility (AXAF) operated as a permanent national observatory in space, to provide x-ray pictures of the Universe comparable in depth and detail with those of the most advanced optical and radio telescopes. Continuing the remarkable development of x-ray technology applied to astronomy during the 1970's, this facility will combine greatly improved angular and spectral resolution with a sensitivity up to one hundred times greater than that of any previous x-ray mission. 2. A Very-Long-Baseline (Vile) Array of radio telescopes designed to produce radio images with an angular resolution of 0.3 milliarcsecond. Among many potential applications of pro- found importance, this instrument will probe the small-scale structure surrounding the enigmatic energy sources in the cores of quasars and active galactic nuclei and will directly determine the distance scale within our Galaxy with un- precedented accuracy. 3. A New Technology Telescope (NTT) of the 15-m class operating from the ground at wavelengths of 0.3 to 20 ~m, to provide a tenfold increase in light-gathering capacity at visual wave

16 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's lengths and a hundredfold increase in speed for spectros- copy at infrared wavelengths, with application to a very wide range of scientific problems. The Committee finds the scientific merit of this instrument to be as high as that of any other facility considered and emphasizes that its priority ranking does not reflect its scientific importance but rather its state of technological readiness. The design studies needed before NIT can be constructed are of the highest priority and should be undertaken immediately. A Large Deployable Reflector in space, to carry out spectro- scopic and imaging observations in the far-infrared and sub- millimeter wavelength regions of the spectrum that are in- accessible to study from the ground, thus extending the powerful capabilities of NIT to these longer wavelengths. Such an instrument, in the 10-m class, will present unprec- edented opportunities for studying molecular and atomic processes that accompany the formation of stars and plan- etary systems. B. Moderate New Programs In rough order of priority, these are: 1. An augmentation to the NASA Explorer program, which remains a flexible and highly cost-effective means to pursue impor- tant new space-science opportunities covering a wide range of objects and nearly every region of the electromagnetic spectrum. 2. A far-ultraviolet spectrograph in space, to carry out a thorough study of the 900-1200-A region of the spectrum, important for studies of stellar evolution, the interstellar medium, and planetary atmospheres. 3. A space VERB interferometer antenna in low-Earth orbit, to extend the powerful VERB! technique into space in parallel with the rapid completion of a ground-based VERB Array, in order to provide more detailed radio maps of complex sources, greater sky coverage, and higher time resolution than the Array can provide alone. 4. The construction of opticallinfrared telescopes in the 2-5-m class, to observe transient phenomena, conduct long-term survey and surveillance programs, provide crucially needed ground- based support to space astronomy, and permit the devel- opment of instrumentation under realistic observing con- ditions. The Committee particularly encourages federal as- sistance for those projects that will also receive significant nonfederal funding for construction and operation.

Recommended Priorities 17 5. An Advanced Solar Observatory in space, to provide observations of our Sun-the nearest star simultaneously at optical, ex- treme ultraviolet, gamma-ray, and x-ray wavelengths, to carry out long-term studies of large-scale circulation, internal dy- namics, high-energy transient phenomena, and coronal ev- olution. 6. A series of cosmic-ray experiments in space, to promote the study of solar and stellar activity, the interstellar medium, the origin of the elements, and violent solar and cosmic processes. 7. An astronomical Searchfor Extraterrestrial Intelligence (SETI), SUp- ported at a modest level, undertaken as a long-term effort rather than as a short-term project, and open to the partic- ipation of the general scientific community. C. Small New Programs The program of highest priority is: · An antenna approximately 10 m in diameter for submilli- meter-wave observations, at an excellent ground-based site. Other programs of outstanding scientific merit, in which the order of listing carries no implication of priority, are as follows: · A spatial interferometer for observations of high angular res- olution in the mid-infrared region of the spectrum; · A program of high-precision optical astrometry; and · A temporary program to maintain scientific expertise at U.S. universities during the 1980's through a series of competitive awards to young astronomers. Detailed discussion and justification of the New Programs appears in Chapter 6. Programs for Study and Development Planning and development are often time-consuming, especially for large projects. It is therefore important during the coming decade to begin study and development of programs that appear to have ex- ceptional promise for the 1990's and beyond. Projects and study areas recommended by the Committee in this category include the follow- ing, in which the order of listing carries no implication of priority: A. Future x-ray observatories in space; B. Instruments for the detection of gravitational waves from as- tronomical objects;

18 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's C. Long-duration spaceflights of infrared telescopes cooled to cry- ogenic temperatures; D. A very large telescope in space for optical, ultraviolet, and near- infrared observations; E. A program of advanced interferometry in the radio, infrared, and optical spectral regions; F. Advanced gamma-ray experiments; and G. Astronomical observatories on the Moon. Detailed discussion of the Programs for Study and Development appears in Chapter 7. ESTIMATED COST OF THE RECOMMENDATIONS In order to establish the overall scale of the recommended total program, the Committee gives in Table 2.1 its own approximate estimates of the requirements for new funding over the next 10 years in millions of 1980 dollars. Funds for projects to be sup- ported by NASA represent research-and-development funds within NASA'S Office of Space Science and Applications (OSSA); funds for projects to be supported by NSF represent total cost to NSF. Op- erating costs are included for those facilities expected to become operational in the 1980's. The funding entries for the Prerequisites for New Research Initi- atives represent augmentations to the present levels of support for these activities within NSF and NASA. As it is expected that the two agencies will work together to coordinate support for the Prerequi- sites, specific agency responsibility is not indicated in the following table. However, since the Prerequisites provide support to space- and ground-based research at comparable levels, the Committee an- ticipates that the funding augmentations to be provided by NASA and NSF will be roughly equal in magnitude. In the cases of the New Programs, the division between space- and ground-based projects is clear. Funds listed for the Explorer program represent an augmentation to NASA'S level-of-effort budget for that program; the operations costs listed for ground-based proj- ects, together with the temporary program to maintain scientific expertise at U.S. universities, represent further augmentations to the operations budget of NSF'S Astronomy Division. Remaining New Program costs represent new-funding requirements for either NASA (new starts within OSSA) or NSF (major construction Within the As- tronomy Division).

Recommended Priorities TABLE 2.1 Requirements for New Funding 19 PREREQu~s~TEs FOR NEW RESEARCH INITIATIVES A. Instrumentation and detectors (doubling of present $15 million/year level of effort by increments over 10 years) B. Theory and data analysis (augmentation by $5 million/ year) C. Computational facilities (30 minicomputer systems in stalled at a rate of 5 systems/year, including opera tions) D. Laboratory astrophysics (augmentation by $2.5 million/ year) E. Technical support at ground-based observatories, in cluding 40 new support positions DECADE TOTAL, PREREQUISITES NEW PROGRAMS A. Major New Programs In order of priority: 1. Advanced X-Ray Astrophysics Facility, (AXAF) 2. Very-Long-Baseline (vLs) Array (including $15 mil- lion for operations) 3. New Technology Telescope (NIT) 4. Large Deployable Reflector in space Decade Subtotal B. Moderate New Programs In rough order of priority: 1. Augmentation to Explorer satellite program 2. Far-ultraviolet spectrograph in space 3. Space VUB interferometry antenna 4. Optical/infrared telescopes in the 2-5-m class 5. Advanced Solar Observatory in space 6. Cosmic-ray experiments 7. An astronomical Search for Extraterrestrial Intelli- gence (SETI) Decade Subtotal C. Small New Programs Of highest priority: · 10-m submillimeter-wave radio antenna (including $2 million for operations) Other important programs: · Spatial interferometer for the mid-infrared (including $1 million for operations) · High-precision optical astrometry program · Temporary program to maintain scientific expertise at U.S. universities Decade Subtotal (Millions of 1980 Dollars) $ 75 50 20 25 20 $190 $500 50 100 300 $950 $200 150 60 20 200 100 20 $750 $ 4 10 $ 20 DECADE TOTAL, NEW PROGRAMS $1,720

20 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's The cost estimates for AXAF and the VUB Array were derived with the help of individual scientists participating in current studies and are based on reasonably complete rough designs. The actual cost of NTT, however, cannot be estimated until further studies indicate which of several alternative conceptual designs will be most cost- effective; the figure given in Table 2.1 is meant as a limit that the Committee recommends should not be substantially exceeded. The estimated cost of the Large Deployable Reflector in space is highly uncertain because instrumentation of this type has not yet been developed and launched. Most of the costs estimated for the Mod- erate New Programs should be reasonable approximations, as they are based on experience with previous instruments of a similar na- ture. The costs given for the augmentation to the NASA Explorer program and for SETI, however, should be regarded as target figures for the level of effort the Committee finds appropriate. The total cost in new funding estimated for the Prerequisites and New Programs together is about $1.9 billion in 1980 dollars. By comparison, the Greenstein report (1972) recommended new pro- grams with an estimated cost of $844 million in 1970 dollars, or approximately $1.7 billion in 1980 dollars, and most of those pro- grams were in fact implemented. The program recommended here for the 1980's is thus roughly comparable in scale with that actually carried out during the 1970's on the basis of the recommendations of the Greenstein report. The Committee wishes to emphasize, however, that the present recommendations will require substantial increases in the budget of the Astronomy Division of NSF, the agency primarily responsible for the support of ground-based astronomy. If, as anticipated, NSF will provide roughly half of the additional funds required for the Pre- requisites for New Research Initiatives, an increase of about 30 per- cent in the Astronomy Division's operations budget over the real level of expenditures during the 1970's will be required for NSF to carry out its share of the recommended program over the next dec- ade. Funds needed by NSF for major construction over the next 10 years will also be substantially higher than those expended during the 1970's, which saw the completion of only one major project, the Very Large Array, at a cost of $78 million. The Astronomy Survey Committee believes that these increases in the NSF budget for ground-based astronomy are essential to maintain an effective partnership with space as- tronomy during the 1980's.

Recommended Priorities BACKGROUND AND OVERVIEW The Greenstein Report 21 The publication of Astronomy and Astrophysics for the 1970's (the Green- stein report) by the National Academy of Sciences in 1972 had a powerful impact on the development of U.S. astronomy and astro- physics during 1972-1982. The federal government on the whole responded positively to its recommendations, with the result that the facilities available to U.S. astronomers have enabled them to remain at the frontiers of research. Here we review the responses to the recommendations of that report and their impact on the prog- ress of science. Radio Astronomy and the VLA The highest-priority recommendation of the Greenstein report was the construction of a Very Large Array (VLA) radio telescope, together with increased support for smaller facilities. Funded by NSF, the VLA was constructed in stages during the 1970's and was formally dedicated in 1980; by far the largest and most complex ground-based astronomical facility established to date, the VLA was completed on schedule and within budget. VLA studies of radio sources are already having a large impact on both Galactic and extragalactic astronomy (see, for example, the cover of this re- port). The recommended increase in funding for smaller radio-astronom- ical facilities did not materialize, however, nor has funding yet been provided for a recommended millimeter-wave radio telescope, then projected to have a diameter of 65 m and to be operable at wave- lengths down to 3 mm. Since the publication of the Greenstein report, the study of interstellar molecules at millimeter wavelengths has yielded insight into the process of star formation; as the science has progressively moved to shorter wavelengths, there has now evolved a need for a smaller, more precisely figured telescope of 25-m di- ameter, still offering high sensitivity and spatial resolution but op- erable at wavelengths down to 1 mm. The recommendation for a large centimeter-wave antenna was not implemented, although ex- isting facilities for observations at wavelengths longer than 1 cm have been maintained and in some cases upgraded. Optical Ground-Based Astronomy The second-priority recommendation was for a variety of steps to enhance the capability available to U.S.

22 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's optical astronomers. A key proposal was the development and con- struction of a multiple-mirror telescope (MMT) with aperture equiv- alent to that of a conventional telescope in the 3.~5.0-m range; this project was to be followed by the construction of a larger MMT, of 10-15-m aperture, if that proved feasible, or by a conventional tel- escope of 5-m aperture if it did not. A 4.5-m MMT has in fact been developed jointly by the Smithsonian Institution and the University of Arizona, becoming operational in 1979. However, neither a larger MMT nor a conventional 5-m telescope has been funded, with the result that the largest instrument available to U.S. optical astrono- mers is still the 5-m Hale telescope on Mt. Palomar, which went into operation 35 years ago. As a result, optical spectroscopy of the faint- est galaxies and quasars discovered by radio and x-ray astronomers has not kept pace with new discoveries, even though these extremely distant objects are of great interest because of their bearing on the nature of cosmic evolutionary processes early in the history of the Universe. The recommendation also called for equipping existing telescopes with advanced electronic detectors and controls. Although major progress was made in the development of such devices during the 1970's, they have so far been provided to only a few major observ- atories. The capability of instruments now available for use on most of the nation's optical telescopes still lags far behind state-of-the-art technology. The Greenstein report furthermore recommended that three tele- scopes in the 2.5-m class be constructed for a variety of purposes. As none of these has been funded, all the nation's major optical telescopes are heavily oversubscribed. Infrared Astronomy The third-priority recommendation called for an across-the-board increase in support for infrared astronomy, which at that time was beginning to demonstrate its great importance. Support has increased substantially, through the funding of two major ground-based infrared telescopes (the 2.3-m University of Wy- oming Infrared Observatory reflector and the 3-m Infrared Telescope Facility operated by NASA on Mauna Kea), the Kuiper Airborne Ob- servatory program, and a balloon program. An international Infrared Astronomy Satellite (IRAS), scheduled for launch in 1982, will carry out a comprehensive, far-infrared survey of the sky, as called for in the Greenstein report. X-Ray and Gamma-Ray Astronomy A series of four High Energy As- tronomical Observatories (HEAD'S) was the fourth-priority recom

Recommended Priorities 23 mendation. In 1973, however) the entire HEAO program was re- structured to reduce costs, and only three HEAD'S were actually flown. Although it had considerably smaller capability than originally planned, the Einstein (HEAo-2) Observatory obtained detailed images of cosmic x-ray sources for the first time, with dramatic implications for a broad range of astronomical research. In gamma-ray astronomy, an important survey was carried out by the Small Astronomical Satellite-B, and further results were obtained by HEAo-3, as well as by balloons and rockets. The most sensitive gamma-ray survey of the sky to date has been carried out by the European Space Agency's COS-B satellite. Other Programs The Greenstein report recommended five other pro- grams, in addition to the four primary recommendations and the two additional radio telescopes mentioned above. A recommended increase in support for aircraft, balloons, and rockets did not occur. The Orbiting Solar Observatory program was not continued as rec- ommended; however, major programs of solar observations were carried out on the Apollo Telescope Mount as part of the manned Skylab program and on the Solar Maximum Mission spacecraft, which carried instruments designed principally for the study of solar flares. Both programs provided important insights into the physical pro- cesses that occur in the solar atmosphere. Theoretical and laboratory astrophysics did not receive the recommended substantial increase, although summer institutes in theoretical astrophyics of the type suggested in the Greenstein report have been implemented at several locations at very low cost and with excellent results. The recom- mended new facilities for astrometry were not funded. Recommendation 9 of the Greenstein report called for an expanded program of optical space astronomy, leading to the launch of a 3.0- m, diffraction-limited Large Space Telescope in the early 1980's. NASA chose instead to develop a somewhat smaller 2.4-m Space Telescope (ST) for launch in 1985 and, in the interim, to extend the lifetime of the oAo-3 (\Copernicus) satellite through the 1970's and to launch the International Ultraviolet Explorer (lUE) in 1978. The high-resolution imaging proposed in Recommendation 9 remains to be realized with ST, although important ultraviolet data are currently being obtained with lUE. Perspective on the Present Survey The internal advisory committees of NSF and NASA including NSF'S Astronomy Advisory Committee and NASA'S Space Science Advisory

24 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's Committee provide effective channels of communication with the scientific community, and they therefore play a significant role in the year-to-year funding decisions faced by these agencies. In ad- dition, since the publication of the Greenstein report, the extent of guidance to NASA on long-range planning for space astronomy has been expanded through the activities of the National Research Coun- cil's (NRC) Space Science Board (SSB), particularly through the sci- entific strategies recommended by SSB'S Committee on Space As- tronomy and Astrophysics (CSAA) and Committee on Solar and Space Physics (cssP). The recommendations of these bodies have increas- ingly helped to shape the course of U.S. space astronomy. Their most recent reports, to which reference will be made below, are the CSAA document, A Strategy for Space Astronomy and Astrophysics for the 1980's (National Academy of Science, Washington, D.C., 1979), and the cssP document, Solar-System Space Physics in the 1980's: A Research Strategy (National Academy of Sciences, Washington, D.C., 1980~. It is therefore not appropriate for a "decade review" such as the Astronomy Survey to prescribe rigidly all agency funding decisions for the next decade. To do so would be to ignore, on the one hand, the guidance available to NSF and NASA from their own internal advisory bodies, particularly in reaction to year-by-year changes in scientific opportunities or in the funding climate; and, on the other, the guidance for space-science strategy already available (and in some cases already in the course of implementation) from the National Academy of Sciences. The present Committee concluded that it could best help to ad- vance astronomical research by focusing its attention on a coordi- nated program of ground- and space-based astronomy that would respond to long-run scientific opportunities. With this in mind, the Committee has limited its recommendations to programs originally proposed for funding in fiscal year 1983 or later, taking account of the earliest time that the publication of the present report could influence the budgets of federal agencies. Projects that were, at the beginning of the survey in 1979, candidates for implementation in fiscal year 1982 or earlier were therefore not considered for inclusion in the Committee's recommendations. A number of important ap- proved and continuing programs are also not explicitly recommended by the Committee, although they form the programmatic base from which the present recommendations proceed. The present status of such projects and programs is as follows: · Space Telescope (ST) and the Space Telescope Science Institute (STSCI). Recommended in the Greenstein report, ST iS now under

Recommended Priorities 25 development and is scheduled for launch in 1985. As recommended in the Space Science Board study, Institutional Arrangements for the Space Telescope (National Academy of Sciences, Washington, D.C., 1976), NASA has established STSC! to direct the ST scientific programs and to support ST users. · Second-generation instrumentation for ST. In its 1979 report, CSAA recommended that ST focal-plane instruments be periodically upgraded in order to fulfill the great scientific potential of ST. · The Gamma Ray Observatory. The 1979 CSAA report listed this facility as one of the five major space-astronomy missions of highest priority for the 1980's. The Gamma Ray Observatory is now an ap- proved NASA program and is projected for launch in 1987-1988. · NASA level-of-effort observational programs, including balloons, aircraft, and sounding rockets, together with the Explorer and Spacelab programs. Strong support for each of these programs was recommended by CSAA in its 1979 report, and other NRC committees have also recommended support for one or more component pro- grams within this group. · The Shuttle Infrared Telescope Facility (SIRTF) and the Solar Op- tical Telescope (SOT) for Spacelab. The 1979 CSAA report recom- mended these projects as the first two major astrophysics facilities for Spacelab; the 1980 cssP report also supported SOT as a facility of high importance for solar physics. SOT, now under development within the Spacelab program, is projected for launch in 1987-1988, while STRTF iS under study by NASA. · Facilities for the detection of neutrinos from the solar interior. An experiment described in the Greenstein report, employing chlo- rine detectors at underground sites, can now be supplemented by investigations employing alternative detector materials, particularly gallium. · Federal grants in support of basic astronomical research at U.S. universities. Such funds, provided primarily through NASA'S Re- search and Analysis program and the grants program of NSF'S As- tronomy Division, are vital to the health of U.S. astronomy. · Programs at the National Astronomy Centers. Adequate support of these programs will permit the Centers to continue to provide an extensive range of observational facilities to a wide and diverse user community. · The 25-Meter Millimeter-Wave Radio Telescope. Recommended in an earlier form in the Greenstein report but not yet funded, this facility has been proposed for the past 4 years as the new program of highest priority in the NSF Astronomy Division's long-range plan. Chapter 4 presents a detailed discussion of the importance of these

:1 26 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's approved, continuing, and previously recommended programs to the health of U.S. astronomy during the 1980's. Assignment of Priorities to Research Needs There is a subtle interplay between science and technology in the pursuit of astronomical research. In more mature areas, such as optical astronomy, the addressing of specific scientific questions re- quires enhanced instrumental capability. In less mature fields, such as gamma-ray astronomy, instruments made possible for the first time by new technology will open up new fields of knowledge, even though the questions we can now ask are less specific. The Com- mittee considered both the scientific questions and the emergence of new technological capabilities as part of the process of assigning . . . priorities. Chapter 3, "Frontiers of Astrophysics," is based on the findings of the Working Groups, which were asked to review the scientific opportunities in a number of subfields of astronomy. With this ma- terial as background, the Committee considered recommendations that had come to it from the Panels, which had been asked to review possibilities for new programs and facilities for the 1980's. The Com- mittee considered the contributions that each proposed program could make in response to the scientific opportunities identified. The final priorities reflect primarily the scientific importance of each program, which is discussed in Chapter 5 (in the case of the Prerequisites for the New Research Initiatives) or in Chapter 6 (in the case of New Programs). In addition, however, the Committee took into account the technological readiness of each program, its ability to complement other programs (either present, planned, or recommended in this report), and its cost. The recommendations identify those activities and facilities that the Committee believes will yield the maximum scientific return for the resources invested. The Committee identified a number of Prerequisites for New Re- search Initiatives, components of the general astronomical research enterprise that are essential to the success of major programs but that are inexpensive in comparison. Each of the Prerequisites should receive a substantial augmentation of funding. The proposed New Programs vary widely in cost. As it is difficult to compare projects of widely differing costs, the Committee grouped the New Programs into three categories-major, moderate, and small, depending on the fraction of agency resources estimated to be re

Recommended Priorities 27 quired and compared projects only with others in the same cate- gory. Assignment of priorities to the four major new programs required intensive discussion, which resulted in unanimous agreement. De- spite its relatively high cost, an instrument having the capability of the Advanced X-Ray Astrophysics Facility (AXAF) iS the highest prior- ity for the 1980's. With the results furnished by the Einstein (HEAo-2) Observatory, x-ray astronomy became a vital part of astronomical research across a broad front. AXAF Will provide astronomers with the capability to carry out a new generation of x-ray observations for a decade or more into the future, complementing the powerful ca- pability of ST in the optical-ultraviolet region and the capability of the VLA and the VERB Array in the radio region. Both the VERB Array (priority 2) and the New Technology Telescope (NTT, priority 3) are extremely important ground-based facilities, but for different reasons. The VERB Array will be able to make observations with extraordinarily high angular resolution of the enigmatic central regions of quasars and will make it possible to determine the size of our Galaxy by entirely new methods. NTT, on the other hand, will make measurements of a more conventional type in the optical- infrared region but with a major advance in speed and penetrating power by comparison with telescopes now available. There is a press- ing need to pursue the implications of data from other wavelength regions, such as radio and x-ray observations, with optical and in- frared spectra of planets, stars, galaxies, and quasars. With double the collecting area now provided by all 20 of the largest telescopes in the world, NTT will greatly accelerate such work and will also make it possible to study spectra of objects whose great distance has so far made it impossible to do so. In the view of the Committee, the construction of the NUB Array and NTT are both of high priority. It will be necessary to complete further, extensive design studies before NTT is initiated, however, whereas the VERB Array utilizes proven technology. For this reason it is recommended that the construction of the Array proceed imme- diately on completion of the overall Array design, while the con- struction of NTT should begin as soon as the more substantial design and cost-estimate studies required for this facility have been com- pleted. The Committee believes that a Large Deployable Reflector (LDR) in space would provide a powerful new capability for sensitive spec- troscopy and accurate imaging at wavelengths between the far-in- frared and millimeter regions of the electromagnetic spectrum. The

28 ASTRONOMY AND ASTROPHYSICS FOR THE 1980's LDR represents the culmination of a coherent, evolutionary program of infrared astronomy proceeding from the capabilities of the ERAS Explorer satellite, the Shuttle Infrared Telescope Facility, and NTT. The priority assigned by the Committee (number 4) reflects the fact that the technology to build such a facility in space is not yet mature; however, it could become so in the second half of the 1980's. The major new programs taken as a whole together with the completed VLA, ST (to be launched in 1985), and Gamma Ray Ob- servatory (projected for launch in 1987-1988) will permit impressive advances to be recorded in astronomical capability across the entire electromagnetic spectrum, from gamma rays to radio waves, includ- ing x-ray, ultraviolet, optical, infrared, and submillimeter radiation. The capability to observe individual objects at various wavelengths greatly increases the scientific value of the data obtained. The recommended moderate new programs address a variety of opportunities in astronomy. One of them, an astronomical Search for Extraterrestrial Intelligence (SETI), was given special consideration by the Committee following the presentation of the report of the Working Group requested to study the possibilities in this area. While the Committee recognized that this endeavor has a character different from that normally associated with astronomical research, intelligent organisms are as much a part of the Universe as stars and galaxies; investigating whether some of the electromagnetic radiation now arriving at Earth was generated by intelligent beings in space may thus be considered a legitimate part of astronomy. Moreover, the techniques that can now be most effectively brought to bear on a SETI program for the 1980's are those of astronomy. In considering implementation of the moderate programs, the Committee did not believe it necessary to assign priorities as precisely as it did for the major projects. The four small new programs recommended were selected from a much larger list of small-scale projects that came to the attention of the Committee. Although there is no implication that other programs of this scale should not also receive serious consideration, the Com- mittee believes that the programs listed are particularly noteworthy. In connection with the last of these a temporary program to main- tain scientific expertise at U.S. universities the Committee benefited from the report of the National Research Council's Commission on Human Resources (Research Excellence Through the Year 2000, National Academy of Sciences, Washington, D.C., 1979), which recommends a more broadly based program of support to young faculty members engaged in scientific research generally. While sympathetic to the

Recommended Priorities 29 Commission's findings, the Committee believed it more appropriate in the present context to recommend a program restricted to astro- nomical research activity, to be funded by the Astronomy Division of NSF. Decisions as to whether to pursue large, medium, or small-scale projects within a given time frame should be made on the basis of current availability of funds, in consultation with the appropriate advisory committees. At the same time, it is recognized that the available funding may not reach the level requested, in which case some modifications may be required. It is recommended that any required stretch-outs or changes in priorities be carried out in such a way as to maximize the scientific return of the overall program. This requires a careful assessment of various factors, including the personnel available in the relevant subdisciplines of astronomy, the balance of effort among subdisciplines, and the need for comple- mentary observations from different wavelength regions and of dif- ferent targets. Such assessments are best carried out by the appro- priate advisory committees on a continuing basis. SUPPLEMENTARY TABULATION OF PROGRAM CHARACTERISTICS Table 2.2 presents the status, specifications, and scientific objec- tives of a selection of the programs discussed earlier in this chapter. It should be emphasized that this listing is intended to supplement such discussions, rather than to provide summaries of all of them. Such a listing will facilitate comparisons among most of the major programs discussed earlier.

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Angular distribution of galaxies brighter than blue magnitude 19, from the Lick Catalog of Galaxies. (Photo courtesy of M. Seldner, B. Siebers, E. J. Groth, and P. J. E. Peebles, Princeton University) -. . I. N~:.~.'~,~ ~:~:'~'\,~'~'~:~ ~ : : ~ He'd I've ~ ~ I: : ~. ~ ~ ~ ~ ~ ~ . ~ ~ .~.~:"~,~'.:~:~'~'~ ~,~ '~"~'~\,~ ~:~ ~':~ ~'~'~.~ :': ~:~

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