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The frequent opportunity to deploy small (SMEX, currently $160 million) and medium-size (MIDEX, currently $300 million) experiments on timescales significantly less than a decade has enabled the United States to seize scientific opportunities, exploit new technologies and techniques, and involve university groups, including students and postdoctoral scholars, in significant development roles. As described in Chapter 5, this capability is essential to training the next generation of scientists and engineers. However, the program’s original intent to deploy an astrophysics SMEX and a MIDEX mission every other year is not being met, given that the launch rate has fallen dramatically to just two per decade. The Announcements of Opportunity (AO) have been so infrequent that the ability to partner with foreign missions has been compromised, and resources have been insufficient to select suborbital platforms, which can be critical to advancing key science goals. The committee therefore recommends, as its second priority in the large category of space-bsed projects, that NASA should support the selection of two new astrophysics MIDEX missions, two new astrophysics SMEX missions, and at least four astrophysics MoOs over the coming decade. AOs should be released on a predictable basis as close to annually as possible, to facilitate missions of opportunity. Further, the committee encourages inclusion of suborbital payload selections, if they offer compelling scientific returns. To accommodate this plan, an annual budget increase would be required for the astrophysics portion of the program from its current average value of about $40 million per year to a steady value of roughly $100 million by 2015. The placement of this recommendation in the large category reflects the decade’s total cost of the augmentation and the committee’s view that expanding the Explorer program is essential to maintaining the breadth and vitality of NASA’s astrophysics program. This is especially true in an era where budgetary constraints limit the number of flagship mission that can be started. Priority 3 (Large, Space). Laser Interferometer Space Antenna (LISA) LISA is a gravity wave observatory that would open an entirely new window in the universe (Figure 7.5). Using ripples in the fabric of space-time caused by the motion of the densest objects in the universe, LISA will detect the mergers of black holes with masses ranging from 10,000 to 10 million solar masses at cosmological distances, and will make a census of compact binary systems throughout the Milky Way. LISA's measurements of black hole mass and spin will be important for understanding the FIGURE 7.5 LISA comprises three spacecraft in an Earth‐trailing orbit. It will be sensitive to waves with periods in the range of 10 seconds to 10 hours. The strain sensitivity is designed to be about 10 ‐20 Hz ‐1/2 . The laser system is a 40‐mW Nd:YAG operating at a wavelength of 1 micron. Credit: NASA. PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION 7-20
significance of mergers in the building of galaxies. LISA also is expected to detect signals from stellarmass compact stellar remnants as they orbit and fall into massive black holes. Detection of such objects would provide exquisitely precise tests of Einstein’s theory of gravity. There may also be waves from unanticipated or exotic sources, such as backgrounds produced during the earliest moments of the universe or cusps associated with cosmic strings. Using three “drag-free” spacecraft launched into an equilateral triangular configuration in an Earth-trailing orbit, LISA would explore the low-frequency (0.1- to 100-mHz) portion of the gravitational wave spectrum, observable only in space, to achieve its scientific objectives. The sides of the triangle are 5 million km, and the “laser-connected” spacecraft would measure their separations to an accuracy enabling detection of tens of picometers relative motions induced by passing gravitational waves. The mission lifetime is planned as 5 years. LISA has been studied for more than 20 years and was recommended by the 2001 astronomy and astrophysics decadal survey and also by two NRC reports. 15 It is a partnership between ESA and NASA that relies on the expertise of both agencies and scientific communities. The ESA portion of the mission is competing for the L-class slot of the Cosmic Vision program; the down-select process is beginning now (the other competitors in this class are IXO, see below, and Laplace, an outer-planets mission), with launch currently scheduled for the end of the decade. In the committee’s independent cost and readiness analysis, the NASA 50 percent portion of the project cost is estimated to be $1.5 billion (at 70 percent confidence), with time to completion of about 9.5 years. The remaining technical risk was rated as medium if the currently identified main technical risks—involving micro-Newton thrusters, drag-free control, and a gravitational reference system—are all retired by a successful LISA Pathfinder (LPF) mission, now scheduled for launch in 2012. The largest remaining technical challenge for the mission is identified as the successful deployment and operation of all three antennas. In recommending LISA, the committee identified two key decision points. First, the LPF mission must be successful. Second, ESA must assign LISA it highest priority as an L-class mission. If either of these conditions is not satisfied, the committee recommends that a decadal survey independent advice committee (DSIAC) be tasked to review the status of LISA mid-decade, in consultation with ESA, and to reconsider LISA’s prioritization relative to other opportunities. Overall the recommendation and prioritization for LISA reflect its compelling science case and the relative level of technical readiness. Assuming a successful Pathfinder, a 2016 new start should enable launch in the middle of the next decade. Priority 4 (Large, Space). International X-ray Observatory (IXO) IXO is a versatile large-area, high-spectral-resolution X-ray observatory (Figure 7.6). X-ray observations probe the hottest regions of the universe, where temperatures reach tens of millions Kelvin. Studying the hot component of the universe is central to understanding how galaxies and larger-scale structures form and how energy and matter cycle through galaxies and the circumgalactic medium, and to probing the observable matter closest to black holes and neutron stars. Hot gas constitutes the majority of ordinary matter in clusters of galaxies. Large-aperture, time-resolved, high-resolution X-ray spectroscopy is required for future progress on all of these fronts, and this is what IXO can deliver. 15 National Research Council, Connecting Quarks with the Cosmos (2003) and NASA’s Beyond Einstein Program: An Architecture for Implementation (2007), The National Academies Press, Washington, D.C. PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION 7-21
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THE NATIONAL ACADEMIES PRESS 500 Fi
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COMMITTEE FOR A DECADAL SURVEY OF A
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Panel on Stars and Stellar Evolutio
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DOUGLAS FINKBEINER, Harvard Univers
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SPACE STUDIES BOARD CHARLES F. KENN
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activities 2 that have emerged from
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In addition to the 27 panel meeting
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Acknowledgment of Reviewers This re
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The Accelerating Universe 2-26 The
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APPENDIXES A Summary of Science Fro
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light up the universe, marking the
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RECOMMENDED PROGRAM Maintaining a b
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TABLE ES.4 Space: Recommended Activ
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Cosmic Dawn: Searching for the Firs
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this imprint would both probe funda
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important outcome will be to open u
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estimated to be on the order of $20
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observatories. For NASA an annual b
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surveys of large fields, enabling s
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RECOMMENDATION: U.S. investors in a
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departments and the community as a
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dominate spending; (2) private-publ
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us was certainly evident during the
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BOX 2-1 Other Worlds Around Other S
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FIGURE 2‐2 The source 3C 75, show
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FIGURE 2‐3 Numerical simulation o
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FIGURE 2‐4 Left panel: Image of t
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FIGURE 2‐6 Top: Schematic of the
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Most stars with masses smaller than
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BOX 2-2 The Origin of Planets After
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send material raining into the cent
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BOX 2-4 Lifecycles in Galaxies One
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Stars Stars are the most observable
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ubiquitous high-energy charged-part
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The Nature of Inflation As describe
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FIGURE 2‐11 Pie chart showing the
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An important clue to the nature of
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Studying the properties of neutron
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FIGURE 2‐14 A possible pathway is
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partners and makes recommendations
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As astronomy research has blossomed
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are increasingly relevant. The Euro
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TABLE 3-1 Currently Operating OIR F
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29% 1990 44% US Priv US Fed Other E
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CONCLUSION: Complex and high-cost f
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Space Observatories The Laser Inter
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Physics Division (PHY); the Mathema
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4 Astronomy in Society Astronomy of
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FIGURE 4‐2 The dust sculptures of
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FIGURE 4‐5 President Obama takes
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Astronomy Inspires in the Classroom
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teaching the scientific method. The
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where the fraction of astronomers h
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Percentage of AAS Membership by Fie
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0.4 0.3 0.2 0.1 PL SO IM AG SF IN S
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FIGURE 4‐12 Number (top panel) an
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Professional training needs to acco
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assistant and associate professor p
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fluctuating level of funding for as
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THEORY Emerging Trends in Theoretic
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Central to the Galaxies across Cosm
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Page 167 and 168: Box 7.1 Implementing a Cosmic Dawn
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Page 225 and 226: NRC NSB NSF NSF-AGS NSF-ARC NSF-AST
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