6
Report of the Panel on Electromagnetic Observations from Space

SUMMARY

NASA’s support of astrophysics research is an essential element in the world-class accomplishments of U.S. astronomers in their exploration of the cosmos. In addition, as was aptly expressed in the first finding of the congressionally requested National Research Council (NRC) study An Enabling Foundation for NASA’s Earth and Space Science Missions, “The mission-enabling activities in SMD [NASA’s Science Mission Directorate]—including support for scientific research and research infrastructure, advanced technology development, and scientific and technical workforce development—are fundamentally important to NASA and to the nation.”1

The Astro2010 Program Prioritization Panel on Electromagnetic Observations from Space (the EOS Panel) reviewed current astrophysics activities supported primarily by NASA’s Science Mission Directorate—specifically, those activities requiring electromagnetic observations from space as distinct from observations of particles or gravitational waves. The charge of the panel was to study possible future activities and to recommend to the Astro2010 Survey Committee a scientifically compelling, balanced, affordable, and relatively low-risk program for the 2010-2020 decade.

1

National Research Council, An Enabling Foundation for NASA’s Earth and Space Science Missions, The National Academies Press, Washington, D.C., 2010, p. 2.



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6 Report of the Panel on Electromagnetic Observations from Space SUMMARY NASA’s support of astrophysics research is an essential element in the world- class accomplishments of U.S. astronomers in their exploration of the cosmos. In addition, as was aptly expressed in the first finding of the congressionally requested National Research Council (NRC) study An Enabling Foundation for NASA’s Earth and Space Science Missions, “The mission-enabling activities in SMD [NASA’s Science Mission Directorate]—including support for scientific research and research infrastructure, advanced technology development, and scientific and technical workforce development—are fundamentally important to NASA and to the nation.”1 The Astro2010 Program Prioritization Panel on Electromagnetic Observations from Space (the EOS Panel) reviewed current astrophysics activities supported primarily by NASA’s Science Mission Directorate—specifically, those activities requiring electromagnetic observations from space as distinct from observations of particles or gravitational waves. The charge of the panel was to study possible future activities and to recommend to the Astro2010 Survey Committee a scien- tifically compelling, balanced, affordable, and relatively low-risk program for the 2010-2020 decade. 1 NationalResearch Council, An Enabling Foundation for NASA’s Earth and Space Science Missions, The National Academies Press, Washington, D.C., 2010, p. 2. 251

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Panel rePorts—new worlds, new HorIzons 252 Guided by the science opportunities identified in the reports of the decadal survey’s five Science Frontiers Panels (Chapters 1 through 5 in this volume) and within the framework of current and in-process facilities and programs available to the astrophysics community, the panel formulated the program described below for electromagnetic space missions for the 2010-2020 decade. In the process of formulating this program, the panel reviewed nearly 100 written submissions from the astronomy and astrophysics community describing a broad range of potential facilities, required tools, and needed technology development, as well as thought- provoking manifestos on process and principles. The program recommended by the panel reflects its judgment that, in the 2010-2020 decade—with many scientifically compelling space missions to choose from but with a tightly constrained budget—the highest priority is for programs that will have a major impact on many of the most important scientific questions, engaging a broad segment of the research community. The panel’s recommended program is divided into large activities and moder- ate/small activities. The panel expresses emphatic support for a balanced program that includes both. The three large initiatives—the Wide-Field Infrared Survey Telescope (WFIRST) Observatory mission, the International X-ray Observatory (IXO) mission, and an exoplanet mission—are presented in prioritized order. The four moderate/small activates are not prioritized. The panel’s recom- mended program calls for strong support of all four activities, although one—the Space Infrared Telescope for Cosmology and Astrophysics and the Background- Limited Infrared-Submillimeter Spectrograph (SPICA/BLISS)—has de facto prior- ity because of its time-critical nature. The moderate/small initiatives are the SPICA/ BLISS initiative, augmentation of NASA’s Explorer program for astrophysics, tech- nology development for a Hubble Space Telescope (HST) successor, and augmenta- tion of NASA research and analysis (R&A) programs in technology development and suborbital science. The relative levels of support for these activities would depend on factors that cannot be forecast in detail, such as (1) the future funding level of NASA’s Astrophysics Division base budget and (2) science opportunities and cost-benefit trade-offs. In the final section (“Funding a Balanced Program”) of this report the panel recommends funding levels across the program that address these issues for three different budget projections for the Astrophysics Division. Large Initiatives Wide-Field Infrared Survey Telescope The WFIRST Observatory is a 1.5-m telescope for near-infrared (IR) imaging and low-resolution spectroscopy. The panel adopted the spacecraft hardware of

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rePort Panel e l e c t r o M a G n e t I c o b s e r vat I o n s sPace 253 of tHe on froM the Joint Dark Energy Mission (JDEM)/Omega mission as proposed to NASA and the Department of Energy (DOE) and substantially broadened the program for this facility. In addition to two dedicated core programs—cosmic acceleration and microlensing planet finding—WFIRST would make large-area surveys of distant galaxies and the Milky Way galaxy, study stellar populations in nearby galaxies, and offer a guest observer program advancing a broad range of astrophysical research topics. International X-ray Observatory The IXO mission, a proposed collaboration of NASA, the European Space Agency (ESA), and the Japan Aerospace Exploration Agency (JAXA), will revo- lutionize X-ray astronomy with its large-aperture and energy-resolving imager. IXO will explore the role of feedback in galaxy evolution by connecting energetic processes within galaxies with the physical state and chemical composition of hot gas around and between galaxies and within galaxy clusters and groups. Time- resolved, high-resolution spectroscopy with IXO will probe the physics of neutron stars and black holes. IXO will measure the evolution of large-scale structure with a dynamic range and detail never before possible. Exoplanet Mission One of the fastest-growing fields in astrophysics is the study of planets beyond our solar system. NASA’s current Kepler and this panel’s recommended WFIRST mission will advance knowedge of the demographics of other planetary systems, but further steps will have to be taken to investigate the properties of individual planets around nearby stars. A micro-arcsecond astrometry mission such as the Space Interferometry Mission (SIM) Lite could detect nearby systems of planets and measure their masses. SIM Lite could even detect Earth-like planets, which are particularly difficult to find, that would be near enough to allow detailed study in more ambitious, future spectroscopic missions. Alternatively, rapid advances in starlight-suppression techniques could enable a moderate-size facility that could image and characterize giant planets (and perhaps some smaller ones) and in- vestigate the debris and dust disks that are stages in the planet-forming process. Discovering even smaller planets and studying their atmospheres with transit photometry and spectroscopy employ another powerful, rapidly improving tech- nique. The panel urges increased technology development for these techniques and recommends that one of these missions, or a yet-to-be-developed approach, be competitively selected around mid-decade and, if the budget permits, started before the end of the decade.

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Panel rePorts—new worlds, new HorIzons 254 Moderate/Small Initiatives Background-Limited Infrared-Submillimeter Spectrograph—U.S. Collaboration on the JAXA-ESA SPICA Mission The tremendous success of the Spitzer Space Telescope has spurred the devel- opment of a yet-more-powerful far-IR mission, the Japanese-led Space Infrared Telescope for Cosmology and Astrophysics. The U.S. community should join this project by making the crucial contribution of a high-sensitivity spectrograph covering far-IR to submillimeter wavelengths, capitalizing on U.S. expertise and experience in detectors and instruments of this kind. Joining SPICA is time-critical and needs to be a priority. Such participation would provide cost-effective access to this advanced facility for the U.S. research community. Because JAXA and ESA are currently moving ahead with SPICA, the panel recommends that NASA commit to participation and begin to fund this activity now. Augmenting the Explorer Program for Astrophysics NASA’s Explorer program is arguably the best value in the space astrophys- ics program. After years of reduced funding, increased support for astrophysics Explorers is essential to a balanced program of research and development (R&D). The panel recommends a substantial augmentation of funding dedicated to astro- physics Explorers with the goal of returning to a flight rate of one Explorer per year by the end of the decade. Technology Development for a Hubble Successor The imperative of understanding the history of the “missing baryons,” as well as the evolution of stars and galaxies, requires ultraviolet (UV) spectroscopic ob- servations that are more sensitive, and at shorter wavelengths, than are possible with the new Cosmic Origins Spectrograph (COS) on the HST. Key advances could be made with a telescope no larger than Hubble but equipped with high-efficiency UV and optical cameras having greater areal coverage than Hubble’s. These would support a very broad range of studies. Achieving these same capabilities with a 4-m or larger aperture, in combination with an exoplanet mission capable of finding and characterizing Earth-like worlds, is a compelling vision that requires further technology development. The panel recommends a dedicated program of major investments in several essential technologies to prepare for what could be the top priority in astrophysics for the 2021-2030 decade.

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rePort Panel e l e c t r o M a G n e t I c o b s e r vat I o n s sPace 255 of tHe on froM Augmenting Research and Analysis Programs in Technology Development and Suborbital Science The NASA Research and Analysis (R&A) programs support diverse activities that are crucial to the astrophysics program. This includes research grants in both observation and theory, as well as for laboratory astrophysics, technology devel- opment, and the Suborbital program. The panel, recognizing that these are core activities that underlie the NASA astrophysics program, recommends as urgent the augmentation of R&A funding that targets technology development and the Suborbital program. The panel calls for (1) a new initiative of focused technology development for projects that are likely to move ahead in the 2021-2030 decade, (2) a more aggressive program of technology development for missions in their conceptual phase, and (3) greater support for the most promising, possibly trans- formational, ideas that are not necessarily tied to a particular mission. The panel also recommends an augmentation of the Suborbital program, which also plays a critical role in developing and testing new technologies while providing a nearly space-like environment for low-cost science and—crucially—the training of new instrumentalists. CONTEXT FOR ELECTROMAGNETIC OBSERVATIONS FROM SPACE IN THE 2010-2020 DECADE An Impressive Suite of Current Missions The remarkable advances in astronomy, astrophysics, cosmology, and funda- mental physics during the past few decades have been achieved to a considerable extent through a broad array of space facilities that cover much of the electromag- netic spectrum. Scientists currently have access to 15 operating space missions (Fig- ure 6.1). Most are NASA-led missions, but some—for example, Planck, Herschel, and Astro-H—are international collaborations in which NASA is a partner. The crucial roles that these facilities play in advancing the field are discussed in Part I of this volume, the reports of the Science Frontiers Panels of the Astro2010 survey. Although a review of that material is beyond the scope of this panel’s report, their contributions, through the scientific priorities identified in the SFP reports, have guided the thinking and the recommendations of the EOS Panel. This broad and powerful suite of capabilities will not continue: most of these missions will reach the ends of their planned lifetimes early in this decade. An important issue early in the decade will be the choice to extend some of these mis- sions that will be made in the NASA Astrophysics Division’s senior review process. The astrophysics community can and should play a role in weighing the scientific

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256 FIGURE 6.1 Astrophysics missions continuing into the 2010-2020 decade. The WISE mission, shown as under development, was launched in Decem- ber 2009 and is now in operation. The termination dates shown are planned at this time and are not a recommendation of this panel. SOURCE: NASA.

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rePort Panel e l e c t r o M a G n e t I c o b s e r vat I o n s sPace 257 of tHe on froM productivity of each mission against the potential of the initiatives recommended in this panel’s report. New and Developing Missions for the Next Decade The Next Generation of Broadly Capable Observatories NASA’s four Great Observatories—Compton, Hubble, Chandra, and Spitzer— are becoming legends in the history of science. Covering the majority of the electro- magnetic spectrum—from gamma rays to the far-IR—these space telescopes have greatly increased our ability to learn what happens in the universe as well as how and why it happens. Not only by providing windows to light that does not reach the ground, but also by offering exquisite spatial resolution and a dark sky, these facilities have been our guides for astronomy’s greatest adventures. A second generation of highly capable, broad-purpose observatories is emerg- ing. They are Fermi, the James Webb Space Telescope (JWST), a proposed new X-ray Observatory, and future large-aperture, UV-optical and far-IR telescopes. To realize all will take decades, but the first—the Fermi Gamma-ray Space Telescope (formerly GLAST)—is already up, surveying the full sky every 3 hours since Au- gust 2008. Fermi’s Large Area Telescope (LAT) covers 20 MeV to ~300 GeV, and its gamma-ray-burst monitor is sensitive over the range 8 keV to 40 MeV. Fermi has already detected active galaxies, pulsars, supernova remnants, compact bina- ries, globular clusters, and gamma-ray bursts (GRBs). New classes of gamma-ray sources have also been discovered: starburst galaxies, high-mass X-ray binaries, and new varieties of gamma-ray-emitting pulsars. Fermi has also made important measurements of the galactic diffuse radiation and precise measurements of the high-energy spectrum of cosmic-ray electrons and positrons. Fermi is a highly successful example of interagency cooperation—NASA and DOE—that includes international partners as well, a matter of relevance to the panel’s first-priority recommendation. The next such observatory will be JWST, the top priority of the previous decadal survey, Astronomy and Astrophysics in the New Millennium (AANM).2 Without a doubt, JWST will be the big space mission of the next decade, indepen- dent of the program advanced by the Astro2010 survey. JWST is a broadly capable observatory in the mold of Hubble, a collaborative project led by NASA, with major participation by the European Space Agency (ESA) and the Canadian Space Agency. JWST will cover a broad range of visible-to-mid-IR wavelengths, 0.6 mm to 28 mm, and will provide orders-of-magnitude greater sensitivity than previous IR space 2 National Research Council, Astronomy and Astrophysics in the New Millennium, National Academy Press, Washington, D.C., 2001.

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Panel rePorts—new worlds, new HorIzons 258 telescopes and with 10 times better angular resolution—comparable to Hubble’s resolution in visible light. Its large 6.5-m segmented primary mirror will view deep space from the Earth-Sun L2 Lagrange point—a million miles from Earth—where the telescope will cool to a frigid 50 K, key for high sensitivity at long wavelengths. JWST’s prime mission is to open the last frontier in galaxy evolution—the earliest generations of stars and the birth of galaxies in the first billion years of cosmic history—and to follow the growth and maturation of galaxies through to the modern era. It will also be a powerful platform for studying how stars and their systems of planets are born in the Milky Way galaxy, taking crucial steps to probe the origin of life itself. The U.S./German Stratospheric Observatory for Infrared Astronomy (SOFIA), a 2.4-m telescope peering into space from the side door of a Boeing 747 aircraft, began science operations in 2010. SOFIA’s near- to far-IR high-resolution spectro- scopic observations are likely to have the greatest scientific impact, but its imaging instruments have unique capabilities as well. SOFIA offers 20 years of operations above the absorbing effects of Earth’s atmosphere, flexible operations from differ- ent locations over the globe to access both sky hemispheres, and the capability of updating and replacing instruments as technologies improve. Not all of this panel’s recommended missions fit into the “broadly capable ob- servatory” category—for example, WFIRST (which will devote most of its lifetime on two dedicated programs and surveys with broad application) and an evolving exoplanet mission do not—but one that certainly does is IXO, a revolutionary X-ray telescope proposed as a collaboration of NASA, ESA, and JAXA. The panel also recommends U.S. participation in the Japanese-led SPICA mission, a large, cold telescope for sensitive far-IR observations of primeval galaxies and of disks where planets form. As a successor to the Spitzer Space Telescope, SPICA is another example of a space observatory that will have substantial impact on a wide range of astrophysics questions. The panel also recommends a dedicated technology- development program that could lead to a large UV-optical telescope—a successor to Hubble—in the 2021-2030 decade. The panel views the 2010-2020 decade as a time of great opportunity to capitalize on the Great Observatories program and leverage its success to this next generation. Smaller Missions in Development for the Next Decade Much astrophysical research requires ambitious, technologically sophisticated, and complex missions like Hubble and JWST. However, progress depends equally on the ingenuity of scientists and the success of parts of the program that em- phasize specific objectives, specialized capabilities, and more flexible and rapidly evolving science programs. The jewel of this approach is the Explorer program. Two decades of astrophys-

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rePort Panel e l e c t r o M a G n e t I c o b s e r vat I o n s sPace 259 of tHe on froM ics Explorers have compiled a stunning record of achievement. In this tradition, the Wide-field Infrared Survey Explorer (WISE), launched successfully in December 2009, has already begun an all-sky survey from 3 to 25 mm that will be hundreds of times more sensitive than that of the Infrared Astronomical Satellite (IRAS) and nearly two orders of magnitude deeper than the JAXA mission Akari. The WISE survey will help search for the origins of planets, stars, and galaxies and create an infrared atlas whose legacy will endure for decades. The Nuclear Spectroscopic Telescope Array (NuSTAR), now in development, will be the first mission to focus high-energy X-rays, pioneering sensitive studies of the “hard” X-ray sky. Scheduled for launch in 2011, NuSTAR will search for black holes, map supernova explosions, and study the most extreme active galactic nuclei (AGN). NASA recently selected for a formulation-phase study the Gravity and Extreme Magnetism Small Explorer (GEMS), a mission that could measure polarization of cosmic X-ray sources and provide unique evidence of a black hole and data on its spin. The United States is also a major participant in the Japanese Astro-H mission, a moderate-aperture X-ray telescope, the novel feature of which will be its rela- tively high sensitivity to moderately hard X-rays, E >10 keV. Among its important instruments will be an imaging array of microcalorimeter spectrometers, built by a U.S. team. Astro-H is expected to give a preview of the revolutionary capabilities of the more ambitious IXO mission. Table 6.1 links this discussion of new and developing missions to recommenda- tions of the two preceeding National Research Council decadal surveys: Astronomy and Astrophysics in the New Millennium (AANM; Taylor-McKee)3 and The Decade of Discovery in Astronomy and Astrophysics (Bahcall).4 SCIENCE DRIVERS FOR KEY NEW FACILITIES The Science Frontiers Panels (SFPs) of the Astro2010 survey have posed key questions that will require new observational capabilities. In Table 6.2 the panel lists these questions and correlates them with the program of activities recommended by the EOS Panel. The Cosmology and Fundamental Physics (CFP) and the Planetary Systems and Star Formation (PSF) SFPs shine their spotlights on what are arguably the most exciting two areas in astrophysics: the study of the extraordinary acceleration of our expanding universe, and exoplanets—expanding the search for and study of the rapidly growing population of planets known to orbit stars other than the Sun. 3 National Research Council, Astronomy and Astrophysics in the New Millennium, National Academy Press, Washington, D.C., 2001. 4 National Research Council, The Decade of Discovery in Astronomy and Astrophysics, National Academy Press, Washington, D.C., 1991.

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Panel rePorts—new worlds, new HorIzons 260 TABLE 6.1 Status of Previously Recommended Space Astrophysics Programs Program Current Status and EOS Panel’s Recommendation 2001 AANMa Recommended Major Next Generation Space Renamed James Webb Space Telescope (JWST), in development for a scheduled Telescope (NGST) launch in 2014. Constellation-X Observatory Reconfigured as International X-ray Observatory (IXO). EOS Panel recommends for this decade (pending ESA selection). Terrestrial Planet Finder (TPF) Several concepts studied and considerable technology development, but not ready for this decade. EOS Panel recommends further technology development. Single Aperture Far-Infrared Not ready. EOS Panel recommends further technology development and Telescope (SAFIR) contribution of far-infrared/submillimeter spectrometer to JAXA-led SPICA mission for this decade. Moderate Gamma-ray Large Area Space Developed jointly by NASA, DOE, and foreign partners. Renamed Fermi. Began Telescope (GLAST) operations in August 2008. Laser Interferometer Space Not reviewed by EOS Panel. Reviewed by Astro2010 Panel on Particle Antenna (LISA) Astrophysics and Gravitation Energetic X-ray Imaging Expanded mission proposed to Astro2010 survey in “Major Category.” EOS Panel Survey Telescope (EXIST) judged the science of insufficient priority to justify high cost and schedule risk as determined by the Astro2010 independent cost appraisal and technical evaluation process. Not recommended by EOS Panel. Small R&A program R&A budgets cut over past decade. EOS Panel recommends budget augmentation for R&A programs, including technology development, theory, laboratory astrophysics, and the Suborbital program. Ultralong-Duration Balloon EOS Panel acknowledges great scientific potential of these longer-duration program and Sounding programs beyond the present Suborbital program and suggests possible payload Rocket to Orbit program support from Missions of Opportunity or Explorer lines. 1991 Bahcall Surveyb Recommended Stratospheric Observatory for Under development by NASA and German Aerospace Center, DLR Telescope Infrared Astronomy (SOFIA) installed and first door-fully-open flight successful. First science in 2010. Space Interferometry Mission Re-endorsed by AANM. Reconfigured and proposed as SIM Lite Astrometric (SIM) Observatory to Astro2010. EOS Panel recommends as a candidate for exoplanet mission with possible start late in the decade. aNational Research Council, Astronomy and Astrophysics in the New Millennium, National Academy Press, Washington, D.C., 2001. bNational Research Council, T he Decade of Discovery in Astronomy and Astrophysics , National Academy Press, Washington, D.C., 1991.

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rePort Panel e l e c t r o M a G n e t I c o b s e r vat I o n s sPace 261 of tHe on froM TABLE 6.2 The Questions Posed by the Astro2010 Science Frontiers Panels, Correlated with the Activities Recommended by the EOS Panel UV- EXO- BLISS Optical Science Frontiers Panel Question/Discovery Area WFIRST IXO PLANET SPICA Telescope PSF-1 How do stars form? PSF-2 How do circumstellar disks evolve and form planetary systems? PSF-3 How diverse are planetary systems? PSF-4 Do habitable worlds exist around other stars, and can we identify the telltale signs of life on an exoplanet? PSF-D Identification and characterization of nearby habitable exoplanets SSE-1 How do rotation and magnetic fields affect stars? SSE-2 What are the progenitors of Type Ia supernovae and how do they explode? SSE-3 How do the lives of massive stars end? SSE-4 What controls the mass, radius, and spin of compact stellar remnants? SSE-D Time-domain surveys GAN-1 What are the flows of matter and energy in the circumgalactic medium? GAN-2 What controls the mass-energy-chemical cycles within galaxies? GAN-3 What is the fossil record of galaxy assembly from the first stars to the present? GAN-4 What are the connections between dark and luminous matter? GAN-D1 Time-domain astronomy GAN-D2 Astrometry GCT-1 How do cosmic structures form and evolve? GCT-2 How do baryons cycle in and out of galaxies, and what do they do while they are there? GCT-3 How do black holes grow, radiate, and influence their surroundings? GCT-4 What were the first objects to light up the universe, and when did they do it? GCT-D The epoch of reionization continued

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Panel rePorts—new worlds, new HorIzons 300 structure lines that signal AGN will fall within the BLISS operating range even at moderate redshifts (z > 0.5), and so BLISS will have unique power to identify AGN from very early times (z ~ 6) to the epoch when they were most common (z ~ 2), and nearly to the present. The high sensitivity and angular resolution of BLISS/ SPICA will let astronomers use far-IR fine-structure lines to probe conditions in star-forming regions within the Milky Way galaxy, for a range of different density and metallicity environments distributed over the galactic disk. It will also be pos- sible to explore protoplanetary disks at the time of formation of gas- and ice-giant planets; giant planets appear to be common, but our current understanding of how they form is very incomplete. The Necessity of a Healthy Explorer Program The Explorer program has been a key component of the NASA portfolio since the earliest days of the space program. The relatively low-cost astrophysics Explor- ers have been highly productive and have provided much of the transformational science of the past 50 years, for example: (1) UHURU, the first X-ray sky survey; (2) IRAS, the first all-sky infrared survey, which discovered protoplanetary dust disks around nearby stars; (3) COBE, finding compelling evidence for the big bang by demonstrating the exact blackbody spectrum of the CMB, detecting the primordial density fluctuations that have led to stars and galaxies, and discovering a cosmic infrared background of starlight absorbed by dust over cosmic time and re-radiated in the IR; and (4) WMAP, mapping the CMB with sufficient precision to measure accurately long-sought cosmological parameters. There are many others. The Explorer program is also an essential programmatic element of the space- science program: (1) it allows focused investigation of key questions not readily addressable with general-purpose missions; (2) it enables relatively rapid response to changing scientific knowledge; and (3) it permits the use of highly innovative technologies at lower risk than would be the case for large missions. The Explorer program was very active between 1995 and 2003, with six MIDEX and five SMEX missions selected for flight (although two were subsequently can- celed) at an average program cost per year of about $200 million (real-year dollars). However, since 2003 there has been a steep drop in the frequency of Explorers: only one astrophysics Explorer has been selected since 2003—the recently chosen Gravity and Extreme Magnetism Small Explorer (GEMS), which is currently in the formulation phase. WISE was launched in December 2009 and NuSTAR is in development, with a launch planned for 2011. Projected budgets for the combined Astrophysics and Heliophysics Explorer programs are projected to increase $170 million per year (real-year dollars) for the next 5 years, significantly below the 1995-2003 level in real terms. Further compounding the problem is the lack of a reliable, affordable launcher for MIDEX-scale missions since the shutdown of the

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rePort Panel e l e c t r o M a G n e t I c o b s e r vat I o n s sPace 301 of tHe on froM Delta II program. The panel strongly recommends that NASA encourage initiatives in private industry to find a robust replacement. Re-establishing a higher launch rate for Explorers would be an important incentive toward that end. The 2000 decadal survey endorsed “a vigorous Explorer program” (AANM, p. 28). The panel endorses that objective as well, reiterating the goal of the astrophys- ics community, and NASA, of an annual astrophysics Explorer launch. The 2006 NRC report Principal-Investigator-Led Missions in the Space Sciences (The National Academies Press, Washington, D.C., 2006) offers extensive advice for strengthening the Explorer program, together with insights from the community that should help to improve its effectiveness as it is re-invigorated. The EOS Panel’s endorsement includes a recommended augmentation of the present support level for astrophys- ics Explorers that would restore a launch rate of one Explorer per year by the end of the decade (see below the section “Funding a Balanced Program”). The Suborbital Program The Suborbital program is a small but essential part of NASA’s overall program of science and technology development. Over the past decade it has had multiple successes across broad areas of science, including measurements of the CMB, IR studies of the early universe, and detection of cosmic rays and even neutrinos. Along the way, suborbital experiments have tested technologies and techniques that enable future missions. Because of the relatively low cost, the program also offers an excellent environment in which to train graduate students and young post- doctoral scientists. Many leading astrophysicists, including many leaders within NASA, gained invaluable early experience in the program. The generic utility of the Suborbital program is widely recognized by the community. Of the programs submitted to the EOS Panel by the community, ~25 percent of them incorporated suborbital work (the bulk of which were for the balloon program), ranging from simple checks of technology, to crucial pathfinders, to full suborbital-based science programs. Easy, cost-effective access to near space is essential. The study of the CMB is a case in point. Our remarkable progress in cosmology is due primarily to innovation in detectors and instruments that continue to push measurements of CMB anisotropies to astonishingly small levels. The CMB com- munity informed the panel that it is working toward a next-generation satellite (a Planck successor named CMBPol) to tackle the exceedingly difficult measurements of CMB B-mode polarization that probe cosmic inflation and gravitational radia- tion from the big bang. The community stated that informing the design of this next mission requires continuation of a combination of technology development, ground-based, and balloon-borne experiments for the next few years. Support is currently at an adequate level, but it is essential that this support, and flight op- portunities, continue. The contingency of the detailed characteristics of CMBPol

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Panel rePorts—new worlds, new HorIzons 302 made it difficult for the panel to prioritize this mission; nevertheless, the panel recognizes how vitally important this research is to astrophysics: the panel gives unqualified, vigorous endorsement to this program. More generally, the Suborbital program has come under increasing stress in recent years by being tapped to subsidize the technology-development program, particularly in the area of new detectors. At the same time, in the case of the bal- loon program, the payloads have become ever more capable and consequently more costly. The net result has been a drastic reduction in the number of payloads that can be supported, and a corresponding reduction in the number of flights. In the coming decade, when budgetary constraints will limit the number of much-more-expensive satellite programs, increasing support for the Suborbital program is a priority. By doubling the access to near space, multiple areas of study will remain vibrant at relatively low cost. This will naturally require a correspond- ing investment in the program offices. In addition to addressing many of the key science objectives of the current decadal survey, it will help to ensure that NASA will enter the following decade in a strong position in terms of technology and expertise. As the capabilities of the Suborbital program increase, the sophistication of the proposed instruments also increases. For example, groups are now proposing coronagraphs from balloon platforms. This bold initiative could provide unique measurements while obtaining invaluable experience with the technology. New ini- tiatives in the ballooning and sounding-rocket programs also have the potential to increase greatly the amount of time available to payloads. The ultralong-duration balloon (ULDB) program will provide 100-day, mid-latitude flights. With suf- ficient support, this relatively mature program could be returning science early in this decade. Over the last decade, the balloon program has dominated the science return from the Suborbital program for astrophysics missions. It seems unlikely that this situation will change without a significant advance in capabilities, for example, with multiorbit sounding rockets with vastly increased integration times. While still only a concept, this could transform the scientific and technological value of the sounding-rocket program. Implementing a program of multiorbit sounding rockets is estimated at $25 million, with subsequent missions costing approximately $15 million. Similarly, while the cost of ULDB missions will be incrementally larger than that of previous ballooning programs, the sophistication of their payloads will require funding levels beyond the program’s current budget. Given the scope of these initiatives, the panel recommends that they should be funded outside the cur- rent program, perhaps competed within the Mission of Opportunity or Explorer lines. This will help to ensure that the low-cost management style of traditional suborbital missions is retained. In the meantime, the EOS Panel recommends that the return on science and technology development be taken as a significant

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rePort Panel e l e c t r o M a G n e t I c o b s e r vat I o n s sPace 303 of tHe on froM consideration when determining the balance of funding between the rocket and balloon programs in the next decade. THE R&A PROGRAM: INCREASING SUPPORT FOR TECHNOLOGY DEVELOPMENT AND THE SUBORBITAL PROGRAM NASA’s R&A program funds a wide variety of essential activities. A $70 million investment in 2008 supported the processing and archiving of data from NASA missions and provided research grants to guest observers to produce science. Of a further $68 million, half was allocated to development programs, including research-grant support for theory and fundamental physics, data analysis tools, and laboratory astrophysics, and half to technology development and the Suborbital program. In this section the panel focuses on the vital contribution of these latter activities and provides a rationale for their increased funding, a step that will, in fact, raise the level of support for all R&A activities. Three Types of Technology Development Activities NASA has built its successes of the last five decades on a foundation of new technology. Continued progress depends on fully developing the technology for high-priority missions, supporting development for future missions, and providing for new enabling technologies for yet-to-be-conceived missions. Missions selected for development support their individual technology needs from the mission line. However, prior to starting formal development, a thorough understanding of the technology is necessary for accurate budgeting and schedul- ing. For this reason, the viability of the high-priority missions recommended in this panel report depends on investments made early in the decade for specific and targeted technologies to bring them to appropriate technology readiness levels (TRLs).11 Examples of the technologies that could be developed under this pro- gram are described below. The missions recommended by the panel will not address some key science goals described in the reports of the Astro2010 Science Frontiers Panels; therefore, some specific areas of technology effort are necessary to develop future missions that will. The longer time-horizon argues against highly targeted development—a more general approach is better at achieving the required advances. Specific exam- ples, such as detector and optics development, are called out in the sections below. Finally, imaginative and innovative approaches to solving problems have al- ways prepared the way for significant leaps in capability. Support of novel ideas is 11 TRL levels range from TRL 1, a basic concept, to TRL 9, proven through a successful mission. TRL 6 is desirable for a technology to be selected for a mission.

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Panel rePorts—new worlds, new HorIzons 304 crucial to the future vitality of NASA, even when some approaches are not directly applicable to planned missions. Indeed, it would have been impossible to predict a decade ago today’s advances in areas such as detector technologies and optics. Technology Development for Recommended Missions Most of the high-priority missions for the next decade already have well- developed programs and technology (Figure 6.17). For example, the WFIRST mission has direct technology heritage from the WFC-3 on Hubble and NIRCam on JWST. While a substantial number of detectors is required, the HgCdTe near-IR detectors for JWST meet all the current requirements for WFIRST. As described above, IXO has been in development in one form or another for more than a decade. Techniques for building efficient large-area mirrors, X-ray microcalorimeters, and gratings are advancing at a pace to allow IXO to enter Phase B by mid-decade. A micro-arcsecond astrometry mission is considered a strong candidate for the next exoplanet mission. At present, SIM Lite is the most thoroughly studied mission, with more than 13 years of design studies. It is ready to enter Phase C and would therefore require minimal technology development. In the EOS Panel’s recommended program, however, an exoplanet mission cannot start until late in the decade. In particular, NASA should ensure that the sophisticated technolo- gies already developed in the SIM program are not lost. However, by later in the decade—when an exoplanet mission might be selected—SIM Lite may not be the best way forward. NASA should continue to respond to new technologies in this area to provide a broad range of options when the time comes. HST WFC WFIRST JWST Optics/gratings, IXO x-ray detectors UV detectors, UV-optical telescope large focal plane arrays Bolometer detectors, BLISS readout electronics, Far-IR missions cryogenics FIGURE 6.17 Near-term technology development for missions recommended by the EOS Panel. 6-17.eps

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rePort Panel e l e c t r o M a G n e t I c o b s e r vat I o n s sPace 305 of tHe on froM A new UV-optical observatory requires significant progress in detector manu- facturing and testing to build large focal plane arrays. These types of detectors might also benefit from suborbital testing. Along the same lines, the BLISS-like instrument for SPICA requires early investment in bolometer detectors, readout electronics, and cryogenics in 2010-2012 to maintain the JAXA/ESA schedule. It is also important to note that such development could feed directly into a U.S.-led far-IR mission in the 2021-2030 timeframe. Technology Development in Support of Future High-Priority Science Increased investment in technologies for missions with possible starts late in the coming decade serves several critical needs for NASA. While WFIRST, IXO, and BLISS for SPICA are well along their technology development paths, there remain key technologies for exoplanet and other possible future missions that will require substantially more work. Attention must also be paid to maintaining expertise: in- sufficiency of resources risks the loss of significant advances already made—many of which would be irretrievable. Finally, testing new technologies on ground-based and suborbital platforms can raise TRLs while returning high-quality science and supporting the field as a whole. Technology for millimeter to far-IR bands has made considerable advancement, fueled early in the decade by work on missions such as Planck and Herschel—and more recently by ground-based and suborbital CMB experiments—and with facil- ity instruments such as SCUBA2 on the JCMT. However, to prepare for future mis- sions like the proposed CMBPol, CALISTO/SAFIRE, and SPIRIT, several key areas need to be addressed. These include large multiplexed arrays of detectors and their associated electronics, cryogenic coolers, and optical designs that address specific systematic effects (Figure 6.18). This field, in particular, benefits substantially from suborbital testing of technology. A number of future planet-finding missions will require significant invest- ments in technology in the coming decade to determine feasibility, risk, and cost. Missions for direct detection of planets in visible light require suppression of starlight to better than 1 part in 1010. Although this level of suppression is deemed a tractable technological problem, significant investments in traditional and non- traditional coronographs, coatings, and deformable mirrors will have to be made. Technology for the Future The directed program outlined above is meant to close technology gaps in order to move ahead with high-priority missions in key science areas. However, new ideas have the potential to revolutionize the field, and so it is important to maintain the current level of support in the R&A program for advanced technolo-

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Panel rePorts—new worlds, new HorIzons 306 Multiplexed arrays of detectors, cryogenic coolers, CMBPol, Far-IR telescope, optics, Far-IR interferometer suborbital flights Starlight suppression High-contrast planet-finding coronagraphy development, UV mission coatings, deformable mirrors UV and optical detectors, wavefront Larger 4+ meter UV optical sensing and control, telescope coatings, occulters, deployable mirrors Gamma-ray detectors Gamma-ray missions FIGURE 6.18 Technology development in support of future high-priority science. gies, particularly ones with the 6-18.epsfor paradigm shifts. Which programs to potential support will, as always, be determined through the peer-review process. Potential areas of advancement include new mirror and optical technologies, star shades, and new types of nulling interferomety (Figure 6.19). To pick one example, external star shades may allow enhanced planet searches with telescopes that are also well suited for ultraviolet observations, thus serving two high-priority science programs and a wide array of science investigations. However, to make star shades feasible it may be necessary to invent new approaches to manufacturing, testing, deployment, and formation flying. These initial explora- tions are appropriate under the current R&A approach, where new ideas are funded based solely on peer review and not on specific development goals. If these issues can be resolved and star shades can approach TRL 3 or 4, a program focused on their application in future missions would become a high priority. This example Mirror and optical technologies UV coatings Future missions Nulling interferometry (e.g., coherent fibers, etc.) FIGURE 6.19 Technology development for the future. 6-19.eps

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rePort Panel e l e c t r o M a G n e t I c o b s e r vat I o n s sPace 307 of tHe on froM illustrates both the importance of an open, peer-reviewed technology program and the necessity of a mechanism to transfer a successful paradigm-shifting technology development to the more focused efforts needed for applications in future missions. An advanced UV-optical telescope would address many of the key questions identified by the Astro2010 Science Frontiers Panels. However, achieving a viable program by the end of the decade will require advances in detector technology, wave-front sensing and control, and UV-optical mirror coatings. Most importantly, new approaches to very lightweight yet highly accurate monolithic or segmented mirrors may be needed. Increased Funding for Technology Development and the Suborbital Program Funding levels largely determine whether required technologies are developed successfully—closing the technology-readiness level gap has always been chal- lenging. Seed money has in the past come from the R&A program. However, the program budget has dropped from $79 million in 2004 to a projected $65 million in 2010 (real-year dollars, based on an annual inflation index of 1.03). Because the R&A program supports a wide variety of research, including technology develop- ment, the Suborbital program, laboratory astrophysics, and theory, all of this re- search has been adversely affected by declining funding levels. While the discussion here focuses on the technology and suborbital programs, all areas will benefit from the recommended budget increases. The panel believes that the R&A program has been strained beyond its ability to meet the needs of NASA: the panel thus recommends a significant increase to correct for declining funding in the 2001-2010 decade. Specifically, $20 million per year inside the current budget should be targeted to technologies that address high-priority science questions not covered by the EOS Panel’s recommendations for new starts in this decade. Based on the documents submitted to the panel by the community, an additional $20 million per year should be distributed more broadly to foster new ideas, with the aim of bringing them to TRL 3 to 5. The panel’s evaluation of the needs for suborbital efforts, based again on documents submitted to the panel, shows that at least an additional $15 million per year is required. For the Suborbital program, the expectation is that $15 million per year in new funding combined with part of the $20 million in recommended new- technology funding will greatly enhance the number of missions. In recognition of the dual role of many suborbital missions, those that have a significant technology component should have access to both lines of resources through a single proposal. There are also some ideas for new, more costly suborbital initiatives (ULDB and sounding-rockets-to-orbit) that would need funding outside the traditional Sub- orbital program, possibly through the Mission of Opportunity or Explorer lines. In summary, the panel recommends an annual augmentation of $35 million to

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Panel rePorts—new worlds, new HorIzons 308 the existing R&A program: $20 million for new technologies, and $15 million for demonstration of technologies and science programs in the Suborbital program. FUNDING A BALANCED PROGRAM Projected NASA budgets provided to the panel show little or no funding for new initiatives before 2014. Thereafter, the completion of JWST leads to substantial, increasing resources in excess of the “base budget,” which includes mission opera- tions, R&A, Missions of Opportunity, and program management. The integral of the funds available for new initiatives from 2014 through 2020 could be as large as $4.0 billion (real-year dollars) with present projections. However, although this figure includes operating funds for JWST and SOFIA, it has no allowance for pos- sible cost growth to complete them, and it does not include continued operations of existing missions such as HST and Chandra after 2015. The panel was also shown a projected budget that included assumptions about these possible added expentitures that arrived at a much lower figure of $2.3 billion for new initiatives in this decade. Conversion of these figures to FY2009 dollars would mean even less money for new initiatives by ~15 percent, unless adjustments for inflation occur. In this final section, the panel attempts to describe the execution of the panel’s recommended program bracketed by these estimates of available funds for new initiatives in the 2010-2020 decade. In Table 6.3 the panel shows funding levels and priorities for the recommended program. The panel takes as a nominal budget the middle ground, the center (green) allocations, $3.1 billion FY2009 dollars, which it considers the minimum balanced program. Sufficient funds are identified to build WFIRST, to augment the Explorer program for astrophysics by $500 million over the period, to start IXO,12 and to fund a small exoplanet mission or start a larger one. The Explorer program, in fact, is part of the base budget, but the panel includes the augmentation it is recommending in the “new initiatives” category because the amount it recommends is too large to be accommodated by changing priori- ties within the base budget. When combined with the present level of funding for astrophysics Explorers, this is a sufficient allocation to raise the launch rate to one per year after 2015. The R&A augmentation (shown in green), which encompasses the additional investments discussed in this section, is intended to be phased in by rearranging priorities of the base budget and as such is not counted here as a new initiative. The U.S. contribution of a BLISS-like spectrometer to SPICA is also as- 12 LISA, the Laser Interferometer Space Antenna, was reviewed and prioritized by the Astro2010’s Particle Astrophysics and Gravity Program Prioritization Panel, and was not subject to EOS Panel review. However, since both LISA and IXO are collaborations with ESA and part of its competition for an L-class mission start, it is unlikely that both will move forward. For purposes of exploring budget profiles and program elements, the IXO slot could therefore be considered to represent either IXO or LISA.

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rePort Panel e l e c t r o M a G n e t I c o b s e r vat I o n s sPace 309 of tHe on froM TABLE 6.3 Funding the EOS Panel’s Recommended Program at Different Levels $3.8 Billion Level $3.1 Billion Level $2.4 Billion Level WFIRST 1.6 1.6 1.6 IXO (start) 1.0 0.7 0.3 Exoplanet 0.7 0.3 — Explorer 0.5 0.5 0.5 R&A 0.3 0.3 0.3 sumed to be within the base budget (a NASA solicitation for science-investigation concept studies for SPICA has already been issued); approximately half of the esti- mated $200 million cost of SPICA participation is projected to occur before 2014. An enhanced budget (blue) would increase the amount spent on IXO through 2020 to $1.0 billion, and allocate $700 million for an exoplanet mission. The exo- planet mission could be a SIM Lite start, a fully funded probe-class mission, or an investment in a more ambitious mission for the following decade. As described above, this choice would be made later in the decade by selective competition between SIM Lite and one of the alternatives discussed in the section “Missions to Search for and Study Exoplanets.” In Table 6.3, the budget below “nominal”—in yellow—would provide a bare start for IXO, but no funding for an exoplanet mission. In this scenario, it is crucial to maintain a healthy Explorer program so that some diverse science goals can still be pursued, albeit at a much more modest level. However, the panel does not consider this level of funding sufficient for a balanced program. In any scenario, the panel gives highest priority to building WFIRST as expedi- tiously as possible, with the goal of launching it within the decade, and then to aug- ment the funding for astrophyscis Explorers as rapidly as possible. Any additional funding should next go to IXO, and then to the Exoplanet mission—consistent with the priorities of this panel’s report. Even in the best case, building IXO will require substantial further investment in the 2021-2030 decade. In the minimal budget case, funding is only sufficient to ensure that IXO would have enough support for technology development to qualify for a new start, a recommendation that would likely defer IXO to the 2020 decadal survey.

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