3 Summaries of Major Reports

3.1 Report of the Workshop on Biology-based Technology to Enhance Human Well-being and Function in Extended Space Exploration

A Report of the Steering Group for the Workshop on Biology-based Technology for Enhanced Space Exploration1

EXECUTIVE SUMMARY

Biological systems are regenerative, energy and size efficient, and adaptable to changing environments. As humans venture further into space and spend longer periods of time there, these attributes may provide the basis for technologies that can sustain life in deep space and on other planets.

This concept was explored at the Workshop on Biology-based Technology to Enhance the Human Presence in Extended Space Exploration, held on October 21-22, 1997, by the Space Studies Board (SSB) of the National Research Council at the Center for Advanced Space Studies in Houston, Texas. The objective was to identify areas in biology-based technology research that appear to hold special promise for carrying biological science into technology directly applicable to space exploration.

Workshop participants sought to identify how biological concepts and principles might contribute to enabling technologies for long-duration missions involving the actual presence of humans (as opposed to robots only) at exploration sites on other planets, such as Mars (see Chapter 1). In the 2010 to 2020 time frame and beyond, NASA proposes to carry out international human missions to planetary bodies such as Mars (a mission of at least 600 days) with no crew rotation or resupply available. Such a mission is beyond today's technical capabilities. Advances are needed in a variety of technical areas to reduce risk, equipment weight, power requirements, and costs as well as to increase reliability.

The workshop's two discussion sessions focused on biology-based research areas with a potential for (1) enhancing human well-being in space exploration and (2) enhancing human presence and function in space exploration. Because the workshop was intended as an initial effort and not a detailed scientific investigation, participants dealt with the discussion topics in a somewhat conceptual manner and did not attempt to assess their merits.

Based on discussions in the two sessions and on their quantitative judgments, participants identified six topics that seem promising enough in the near term to warrant further examination in follow-on workshops: closed-loop

1  

“Executive Summary” reprinted from Report of the Workshop on Biology-based Technology to Enhance Human Well-being and Function in Extended Space Exploration, National Academy Press, Washington, D.C., 1998, pp. 1-6.



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Space Studies Board 3 Summaries of Major Reports 3.1 Report of the Workshop on Biology-based Technology to Enhance Human Well-being and Function in Extended Space Exploration A Report of the Steering Group for the Workshop on Biology-based Technology for Enhanced Space Exploration1 EXECUTIVE SUMMARY Biological systems are regenerative, energy and size efficient, and adaptable to changing environments. As humans venture further into space and spend longer periods of time there, these attributes may provide the basis for technologies that can sustain life in deep space and on other planets. This concept was explored at the Workshop on Biology-based Technology to Enhance the Human Presence in Extended Space Exploration, held on October 21-22, 1997, by the Space Studies Board (SSB) of the National Research Council at the Center for Advanced Space Studies in Houston, Texas. The objective was to identify areas in biology-based technology research that appear to hold special promise for carrying biological science into technology directly applicable to space exploration. Workshop participants sought to identify how biological concepts and principles might contribute to enabling technologies for long-duration missions involving the actual presence of humans (as opposed to robots only) at exploration sites on other planets, such as Mars (see Chapter 1). In the 2010 to 2020 time frame and beyond, NASA proposes to carry out international human missions to planetary bodies such as Mars (a mission of at least 600 days) with no crew rotation or resupply available. Such a mission is beyond today's technical capabilities. Advances are needed in a variety of technical areas to reduce risk, equipment weight, power requirements, and costs as well as to increase reliability. The workshop's two discussion sessions focused on biology-based research areas with a potential for (1) enhancing human well-being in space exploration and (2) enhancing human presence and function in space exploration. Because the workshop was intended as an initial effort and not a detailed scientific investigation, participants dealt with the discussion topics in a somewhat conceptual manner and did not attempt to assess their merits. Based on discussions in the two sessions and on their quantitative judgments, participants identified six topics that seem promising enough in the near term to warrant further examination in follow-on workshops: closed-loop 1   “Executive Summary” reprinted from Report of the Workshop on Biology-based Technology to Enhance Human Well-being and Function in Extended Space Exploration, National Academy Press, Washington, D.C., 1998, pp. 1-6.

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Space Studies Board aquaculture systems as a model for advanced life support (ALS) water processing and waste management systems; biosensors for detecting pollutants and pathogens in air and water; biomaterials for spacecraft and habitats; space suit design incorporating biological concepts; use of magnetoencephalography to monitor astronauts' cognitive states; and synergistic human-robot systems. Also identified in each session were additional areas in which R&D advances by NASA or others may benefit the space program either in the near term or over the longer term. The concepts discussed in sessions 1 and 2 are described in Chapters 2 and 3, respectively. Chapter 4 touches briefly on workshop participants' observations regarding points for considerations in any follow-on activities—including the importance of defining specific technical requirements for long-duration human exploration of space and the usefulness of tracking developments in fields other than aeronautics and space science that may contribute to the application of biology-based systems and principles in Human Exploration and Development of Space (HEDS) Enterprise missions. OPPORTUNITIES FOR APPLYING BIOLOGICAL CONCEPTS AND PRINCIPLES Enhancing Human Well-Being Session 1 participants sought to identify biological concepts and principles that might be further explored to address needs related to regenerative advanced life support (ALS) systems, spacecraft and habitats, and the health of humans and useful biological organisms. A central theme was the value of reducing, reusing, recycling, and recovering materials so as to reduce size, mass, and power requirements (and thus cost) as well as increase reliability for long-term human exploration of space. Session 1 participants identified three topics that seem promising for exploration in follow-on workshops, as well as two research areas that might offer NASA short-term payoffs and two that might offer longer-term payoffs. Topics for Follow-on Workshops Closed-loop Aquaculture Systems as a Model for ALS Water Processing and Waste Management Systems. Provision of clean water is a basic requirement for extended space exploration missions. A workshop on current technologies in the maturing field of closed-loop aquaculture and innovative fermentation processes used in waste treatment might assist in the development of highly efficient closed-loop regenerative ALS systems for extended space missions. Biosensors for Detecting Pollutants and Pathogens in Air and Water. To maintain human health and comfort as well as functioning plant and microbial populations, rapid and reliable detection and monitoring systems are needed to ensure that air and water in spacecraft and in habitats do not contain disease-causing pathogens or discomfort-causing levels of pollutants. Potential applications of biosensors could be explored in a workshop that would also have to define the research required to identify which microorganisms and pollutants should be detected on spacecraft and habitats and to establish sensitivity requirements relevant to NASA's needs. The use of biosensors in the skin of planetary habitats that could alert the crew to radiation levels and/or level of radiation-induced damage could also be addressed as part of this follow-on workshop. Biomaterials for Spacecraft and Habitats. Biomaterials and biologically inspired materials might incorporate capabilities ranging from self-diagnosis and self-repair of certain system components to protection of astronauts and other biological organisms from the effects of radiation. Furthermore, such materials could also help make missions to other planets possible by virtue of their being lightweight and renewable, offering opportunities to reduce transportation cost and mass. These and other potential attributes as well as trade-offs in labor, space, and energy should be examined in a focused workshop before specific biomaterials are used in space applications. Research Areas Offering Short-Term Payoffs Cultivation of Algae as Food. Algae and cyanobacteria are used as nutritional supplements on Earth and might be cultivated for that purpose on spacecraft, as well as for waste treatment, CO2 recycling, and O2 generation. In addition to identifying edible species that could be grown in the space environment, it may also be worth exploring

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Space Studies Board the genetic engineering of algae and/or cyanobacteria to enhance their value and palatability as food, or the development of suitable food processing methods to either remove or degrade undesirable components (such as nucleic acids). Because cyanobacteria are more easily cultured and genetically engineered than eukaryotic algae or higher plants, they may hold greater promise in the short run for use in air recycling, wastewater treatment, and food production. The significant base of information on algae and cyanobacteria needs to be reexamined to identify their potential for use in such applications. Development of Plants with Enhanced Disease Resistance. The types of diseases likely to occur in space horticulture must be identified so that plants resistant to specific diseases can be developed. Research is also needed to enable identification and management of the relevant disease-causing organisms. Enzymatic Catalysts for Housekeeping. Humidity control is probably key to preventing overgrowth of microorganisms, which can also become resistant to the biocides used to wipe down bulkheads. When cleaning is necessary, enzymes (e.g., proteases, lipases) can be used as alternatives to chemical cleaning agents, an approach that has emerged for industrial cleaning applications. Enzymes, which are naturally occurring proteins, can be designed to target the compounds that enable microorganisms to adhere to surfaces. Furthermore, enzymes are highly suitable for spaceflight because they are lightweight, biodegradable, and have a long shelf life. However, some enzymes may cause allergies. Research is needed to examine the feasibility of using enzymes for housekeeping in spacecraft and planetary habitats, and to evaluate risks of exposing crew members to these potentially potent allergens. Research Areas Offering Long-Term Payoffs Genetic Engineering of Plants. Plants, a fundamental biological system, will be essential to human well-being in long-duration space exploration. Plants can be used not only as food but also as sources of useful materials and chemicals and for the recycling of carbon dioxide and other inorganic and organic wastes. To meet defined requirements for spaceflight, plants might be engineered, for example, to produce miniature roots or leaves, grow under low-light conditions, exhibit increased resistance to disease or radiation, and produce structural materials such as biodegradable plastics or specific nutrients needed by humans. Radiation Protection and Monitoring. Certain plants and microorganisms have effective DNA-repair mechanisms that confer some measure of radiation resistance or tolerance. Research aimed at understanding such mechanisms might provide a basis for transferring these capabilities to plants and organisms cultivated on spacecraft. It may also be possible to design a biological dosimeter for radiation monitoring through the use of specific microorganisms or designed DNA integrated into biochips for monitoring purposes. The applicability of advanced biological dosimeters for space exploration could be addressed as part of the workshop on biosensors suggested above. Enhancing Human Presence and Function Session 2 participants sought to identify biological concepts and principles that might enhance human function in four areas: perception, manipulation and locomotion, cognition, and systems and computation. The group discussions reflected a number of themes, including similarities between deep space and the deep ocean that suggest a potential for transferring diving technologies and concepts to the space program; the merits of biological concepts as models for processes that are inherently simple and evolutionary, as opposed to complex and excessively mechanical; and the need to strike an appropriate balance between the tasks assigned to machines versus those assigned to humans. The group identified three topics that seem promising enough in the short term to be addressed at follow-on workshops. Topics for Follow-on Workshops Space Suit Design Incorporating Biological Concepts. As part of the effort to design lightweight space suits suitable for use on Mars, biological concepts and principles could be applied to enhance astronauts' comfort and function. A future workshop could explore, for example, the application of biomechanical concepts such as 40-degree-angle wrist settings to provide maximum dexterity and grip, biomolecular materials modeled on strong yet dexterous sharkskin, technologies such as actuators and microelectrical mechanical systems (MEMS) that could

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Space Studies Board assist with movement or self-repair, external sensors that produce haptic and other sensory feedback to the astronaut, and galvanic stimulation to provide cues about spatial orientation in microgravity. Use of Magnetoencephalography to Monitor Astronauts' Cognitive States. Physiological monitoring of brain waves could provide confidential biofeedback on astronauts' cognitive states for the purpose of enhancing functional effectiveness and promoting relaxation. Magnetoencephalography, which is based on the use of superconducting quantum interference devices (SQUIDs) to detect very small magnetic fields, offers a number of advantages, including rapid response and ease of use. A SQUID cryogenic cap or helmet for recording brain waves may be particularly appropriate in the space environment, where temperatures are theoretically cold enough to make the SQUIDs superconducting. A future workshop could explore the benefits and feasibility of designing such a system. Synergistic Human-Robot Systems. A future workshop could explore the design of synergistic human-robot systems that would meet needs for system reliability and configurability, effective human-machine collaboration, improved situational awareness, and optimal decision making. Three biology-based concepts seem particularly promising: (1) collaborative multirobot systems modeled on the task sharing of the insect kingdom. Advantages include rapid adaptation to the loss of individual robots, robust communication among all robotic or biological elements, system reconfigurability, and the capability to deploy specialized individuals. (2) Robotics systems that exhibit emergent system behavior mediated by emotion and anxiety, as well as a learning process augmented by emotion. Such systems would “think” more like humans, whose decision-making and problem-solving abilities are improved by access to their emotions. (3) Interfaces that enable human comprehension of system data without information overload, and the communication of human affect and intentions to robots. Research Areas Offering Short-Term Payoffs Artificial Vision Systems. Technologies being actively investigated in many sectors offer the possibility of enhancing human vision and providing new modalities, such as over-the-horizon sight. However, existing devices tend to be bulky, primitive, and, in most cases, far less sensitive, precise, or adaptive than their biological counterparts. The state of the art needs to be improved. Of particular interest is using very large-scale integration (VLSI) and MEMS technology to integrate sensing, processing, and possibly display elements into small, light-weight, low-power units. Biological principles and biology-inspired designs could provide critical guidance in such efforts. For instance, visual computational sensors or artificial retinas that provide spatio-temporal processing at the place of sensing could enable task-oriented, rapidly adaptable processing of visual information. Exercise Based on Biological Concepts. As an alternative or supplement to the treadmill currently used for exercise during spaceflight, it might be useful to explore an exercise concept that mimics the activities of an embryo during its time in the womb. A “bungee suit” with elastic properties might be designed that would enable gymnastics regimens that could maintain or restore an astronaut's physical state. Research Areas Offering Long-Term Payoffs Adaptation to Different Gravitational States. Astronauts' adaptation to microgravity and subsequent readaptation to Earth's gravity might be accelerated by understanding and manipulating the fragile transition between the two states. Evidence from everyday life and biomedical research—including a rapid increase in understanding of the central nervous system and its plasticity—points to an inherent biological capability for dual adaptation. A combination of pharmacological intervention and appropriate training and exercise might effectively prepare astronauts for adaptation to alternating gravitational states. Software for Emotion-Mediated Learning. In humans, emotional states mediate decision making and learning. Software for robotics systems could be designed to exhibit emergent system behavior mediated by emotion and anxiety, and a learning process augmented by emotion. Such systems might meet needs for software reliability and configurability, effective human-machine collaboration, improved situational awareness, and optimal decision making.

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Space Studies Board “Principal Investigator (PI) in a Box.” Given the complexity and new challenges associated with long-term human exploration of space, astronauts might benefit from having instant access to a database of the accumulated experience of previous astronauts. The database could support dynamic mission planning and execution strategies and improved problem solving and could be self-organizing to respond to immediate needs. Biology-based concepts could also be applied to the presentation of data. For example, algorithms based on the survival instinct might present data on the most life-threatening situation first.

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Space Studies Board 3.2 The Exploration of Near-Earth Objects A Report of the Committee on Planetary and Lunar Exploration1 EXECUTIVE SUMMARY Near-Earth objects (NEOs) are asteroids and comets with orbits that intersect or pass near that of our planet. About 400 NEOs are currently known, but the entire population contains perhaps 3000 objects with diameters larger than 1 km. These objects, thought to be similar in many ways to the ancient planetesimal swarms that accreted to form the planets, are interesting and highly accessible targets for scientific research. They carry records of the solar system's birth and the geologic evolution of small bodies in the interplanetary region. Because collisions of NEOs with Earth pose a finite hazard to life, the exploration of these objects is particularly urgent. Devising appropriate risk-avoidance strategies requires quantitative characterization of NEOs. They may also serve as resources for use by future human exploration missions. The scientific goals of a focused NEO exploration program are to determine their orbital distribution, physical characteristics, composition, and origin. Physical characteristics, such as size, shape, and spin properties, have been measured for approximately 80 NEOs using observations at infrared, radar, and visible wavelengths. Mineralogical compositions of a comparable number of NEOs have been inferred from visible and near-infrared spectroscopy. The formation and geologic histories of NEOs and related main-belt asteroids are currently inferred from studies of meteorites and from Galileo and Near-Earth Asteroid Rendezvous spacecraft flybys of three main-belt asteroids. Some progress has also been made in associating specific types of meteorites with main-belt asteroids, which probably are the parent bodies of most NEOs. The levels of discovery of NEOs in the future will certainly increase because of the application of new detection systems. The rate of discovery may increase by an order of magnitude, allowing the majority of Earth-crossing asteroids and comets with diameters greater than 1 km to be discovered in the next decade. A small fraction of NEOs are particularly accessible for exploration by spacecraft. To identify the exploration targets of highest scientific interest, the orbits and classification of a large number of NEOs should be determined by telescopic observations. Desired characterization would also include measurements of size, mass, shape, surface composition and heterogeneity, gas and dust emission, and rotation. Laboratory studies of meteorites can focus NEO exploration objectives and quantify the information obtained from telescopes. Once high-priority targets have been identified, various kinds of spacecraft missions (flyby, rendezvous, and sample return) can be designed. Some currently operational (Near-Earth Asteroid Rendezvous [NEAR]) or planned (Deep Space 1) U.S. missions are of the first two types, and other planned U.S. (Stardust) and Japanese (Muses-C) spacecraft missions will return samples. Rendezvous missions with sample return are particularly desirable from a scientific perspective because of the very great differences in the analytical capabilities that can be brought to bear in orbit and in the laboratory setting. Although it would be difficult to justify human exploration of NEOs on the basis of cost-benefit analysis of scientific results alone, a strong case can be made for starting with NEOs if the decision to carry out human exploration beyond low Earth orbit is made for other reasons. Some NEOs are especially attractive targets for astronaut missions because of their orbital accessibility and short flight duration. Because they represent deepspace exploration at an intermediate level of technical challenge, these missions would also serve as stepping stones for human missions to Mars. Human exploration of NEOs would provide significant advances in observational and sampling capabilities. The Committee on Planetary and Lunar Exploration (COMPLEX) has considered appropriate baseline research efforts, as well as a number of augmentations to existing programs for the discovery and characterization of NEOs. With respect to ground-based telescopic studies, the recommended baseline is that NASA and other appropriate agencies support research programs for interpreting the spectra of near-Earth objects (NEOs), continue and coordinate currently supported surveys to discover and determine the orbits of NEOs, and develop policies for the public disclosure of results relating to potential hazards. Augmentations to this baseline program include, in priority order, that relevant organizations do the following: 1   “Executive Summary” reprinted from The Exploration of Near-Earth Objects, National Academy Press, Washington, D.C., 1998, pp. 1-2.

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Space Studies Board Provide routine or priority access to existing ground-based optical and infrared telescopes and radar facilities for characterization of NEOs during favorable encounters, or Provide expanded, dedicated telescope access for characterization of NEOs. The baseline recommendation with respect to laboratory studies and instrumentation is that NASA and other appropriate agencies should support continued research on extraterrestrial materials to understand the controls on spectra of NEOs and the physical processes that alter asteroid and comet surface materials. An appropriate augmentation to this baseline is to support the acquisition and development of new analytical instruments needed for further studies of extraterrestrial materials and for characterization of returned NEO samples. Spacecraft missions and the development of the associated technology and instrumentation are essential components of any program for the study of NEOs. The baseline recommendation in this area is to support NEO flyby and rendezvous missions. Appropriate augmentations include, in priority order, that relevant organizations do the following: Develop technological advances in spacecraft capabilities, including nonchemical propulsion and autonomous navigation systems, low-power and low-mass analytical instrumentation for remote and in situ studies, and multiple penetrators and other sampling and sample-handling systems to allow low-cost rendezvous and sample-return missions. Study technical requirements for human expeditions to NEOs. Although studies evaluating the risk of asteroid collisions with Earth and the means of averting them are desirable, they are beyond the scope of this report.

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Space Studies Board 3.3 Exploring the Trans-Neptunian Solar System A Report of the Committee on Planetary and Lunar Exploration* EXECUTIVE SUMMARY A profound question for scientists, philosophers and, indeed, all humans concerns how the solar system originated and subsequently evolved. To understand the solar system's formation, it is necessary to document fully the chemical and physical makeup of its components today, particularly those parts thought to retain clues about primordial conditions and processes.1 In the past decade, our knowledge of the outermost, or trans-neptunian, region of the solar system has been transformed as a result of Earth-based observations of the Pluto-Charon system, Voyager 2's encounter with Neptune and its satellite Triton, and recent discoveries of dozens of bodies near to or beyond the orbit of Neptune. As a class, these newly detected objects, along with Pluto, Charon, and Triton, occupy the inner region of a hitherto unexplored component of the solar system, the Kuiper Belt. The Kuiper Belt is believed to be a reservoir of primordial objects of the type that formed in the solar nebula and eventually accreted to form the major planets. The Kuiper Belt is also thought to be the source of short-period comets and a population of icy bodies, the Centaurs, with orbits among the giant planets. Additional components of the distant outer solar system, such as dust and the Oort comet cloud, as well as the planet Neptune itself, are not discussed in this report. Our increasing knowledge of the trans-neptunian solar system has been matched by a corresponding increase in our capabilities for remote and in situ observation of these distant regions. Over the next 10 to 15 years, a new generation of ground- and space-based instruments, including the Keck and Gemini telescopes and the Space Infrared Telescope Facility, will greatly expand our ability to search for and conduct physical and chemical studies on these distant bodies. Over the same time span, a new generation of lightweight spacecraft should become available and enable the first missions designed specifically to explore the icy bodies that orbit 30 astronomical units (AU) or more from the Sun. The combination of new knowledge, plus the technological capability to greatly expand this knowledge over the next decade or so, makes this a particularly opportune time to review current understanding of the trans-neptunian solar system and to begin planning for the future exploration of this distant realm. Based on current knowledge, studies of trans-neptunian objects are important for a variety of reasons that can be summarized under five themes: Exploration of new territory. Telescopic discoveries of new Kuiper Belt objects (KBOs) are being made monthly. With continued access to suitable telescopes, this rate of discovery will likely be maintained for many years since very little of the sky (<0.1% of the ecliptic for objects brighter than 17th magnitude)2,3 has been surveyed to date. While telescopes are showing us that trans-neptunian objects are relatively common and are providing information about their disk-averaged surface composition, spacecraft missions are necessary to explore the detailed nature of these icy bodies. Reservoirs of primitive materials. While KBOs may not be pristine relics of the original solar nebula, it is in the outer solar system that we might expect to find the least-modified materials as well as samples that have suffered a range of degrees of modification. These bodies can provide the links for understanding the relationships among the interstellar medium, the solar nebula, and current materials in the solar system. Processes that reveal the solar system's origin and evolution. The observable characteristics of objects tell us about the processes they have experienced. The distribution of a population of objects in orbital phase space provides clues about their origins and the dynamical processes that control them over long periods. The distribution of sizes within a population reveals the relative importance of accretion versus collisional erosion. The wide range of sizes and different collisional histories among objects in the trans-neptunian region implies varying degrees of internal differentiation. Surface geology provides important constraints on an object's thermal history. Surface chemistry and atmospheric properties reveal processes of outgassing, photochemistry, transport, and redeposition of volatiles. * “Executive Summary” reprinted from Exploring the Trans-Neptunian Solar System, National Academy Press, Washington, D.C., 1998, pp. 1-6.

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Space Studies Board Links to extrasolar planets. Studies of early stars similar to the Sun have shown that some are surrounded by disks of dust that are thought to be derived from collisions between comets. It is natural, therefore, to relate such dust disks to the Kuiper Belt. Applying knowledge of the Kuiper Belt to stellar dust disks suggests that the inner boundary exhibited by some disks may be an indication of the existence of planets. Comparisons of the Kuiper Belt with these dust disks is an important component of the new field of comparative studies of solar systems. Prebiotic chemistry. As remnants of the early solar system, trans-neptunian objects can provide critical clues about processes of prebiotic chemistry and about the materials that would have been delivered to the early Earth and may have formed the source of volatile materials from which life arose here and possibly on other planets of this and other solar systems. These five themes are not on an equal footing. The first three are well-established areas of scientific investigation and are backed up by a substantial body of observational and theoretical understanding. The last two, however, are more speculative. They are included here because they raise a number of interesting possibilities that seem particularly suited to an interdisciplinary approach uniting planetary scientists with their colleagues in the astrophysical and life science communities. Although not considered in any detail in this report, the distant outer solar system also has direct relevance to Earth and the other terrestrial planets because it is the source of comets that bring volatiles into the inner solar system. The resulting inevitable impacts between comets and other planetary bodies can play a major role in the evolution of planetary surfaces and atmospheres. Indeed, comets can also play major roles in the evolution of life as suggested by, for example, the Cretaceous-Tertiary boundary bolide and the extinction of the dinosaurs. TRANS-NEPTUNIAN OBJECTS The five major themes described above involve general scientific issues that apply to the trans-neptunian region as a whole. Below COMPLEX summarizes the current knowledge and outstanding issues of the separate major types of objects in the trans-neptunian region. Triton Triton is by far the best-explored icy body in the distant outer solar system,4 and, as such, sets the context for the discussion of the other bodies. Triton is thought to be a planetary body that was captured by Neptune in the distant past. Voyager 2's flyby of Triton demonstrated the wealth of information available only from a spacecraft mission. Triton 's density suggests that it has a rock core (70% by mass) surrounded by ice. Tidal heating due to orbital evolution and/or collision(s) with other satellites probably caused differentiation of the interior. Geological mapping indicates a youthful surface with few impact craters and with active volcanic eruptions. Its surface is uniformly cold (<38 Kelvin) and is covered with patches of volatile ices that appear to be strongly coupled to Triton's seasonally varying nitrogen atmosphere. The outstanding issues at Triton are as follows: When and by what process was Triton captured by Neptune? What is the degree of differentiation of the interior? Does Triton have an iron core and/or magnetic field? What drives the volcanism? How are the volatile ices brought to the surface and distributed? What is the distribution of surface materials, and how are they related to geological units? What are the structure and dynamics of Triton's atmosphere, and how do they vary with Triton's complex seasonal pattern? Pluto and Charon Pluto is both the smallest planet and the largest body in the outer solar system that is not in orbit around a giant planet. Our knowledge of Pluto and its satellite, Charon, is limited to telescopic observations. Other than the identification of certain ices on Pluto and Charon and the observation of strong variations in albedo on Pluto, little

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Space Studies Board can be said about their surfaces or geology, beyond speculation based on knowledge of other icy satellites. As with Triton, Pluto's atmosphere is strongly coupled to the surface volatiles so that differences in their atmospheres result from the different nature of their surfaces. Pluto's warmer atmosphere and enhanced methane abundance are consistent with the ice on Pluto's surface containing 30 times more methane than Triton's ices and with large dark regions where the surface must be warmer. Charon's capture by Pluto probably involved a disruptive collision of the two bodies. The outstanding issues at Pluto and Charon are as follows: What are the bulk densities of Pluto and Charon? What are the interior composition and the state of differentiation of Pluto and Charon? What were the effects of the initial collision and subsequent tidal stresses produced in each body as a result of Charon's capture by Pluto? Is there activity on the surfaces of Pluto or Charon (e.g., plumes as on Triton)? Are the large-scale variations in albedo on Pluto due to variations in crustal structure or frost deposits? What is the structure of Pluto's atmosphere, and how does it change with time? Why is Pluto's atmosphere so different from Triton's? Kuiper Belt Objects Very little is known about the approximately 60 KBOs detected to date. Measurements of their orbits suggest that many of them are in resonance with Neptune. Variations in brightness are attributed to variations in size but cannot be quantified accurately without information on albedos. Measurement of brightness at different wavelengths gives an indication of surface color, and suggests that surface compositions may vary among KBOs. Outstanding issues for Kuiper Belt objects are the following: What fraction of KBOs are in dynamically evolved orbits? What is the rate at which their orbits are perturbed sufficiently to send KBOs inward where they might interact with the giant planets? What does the size distribution of KBOs tell us about their accretion and erosion? If the range in observed colors is a true indication of diversity in surface composition, what causes this diversity? What is the degree of differentiation of these small bodies? Centaurs Other than spectroscopic observations that indicate diverse surface compositions, very little information is available about the half-dozen objects with eccentric orbits among the giant planets. Outstanding issues for the Centaurs are these: How many Centaurs are there? What are their orbits and how did these objects get where they are? How did their orbits evolve from the Kuiper Belt? What causes their color diversity? Does Chiron have a bound dust atmosphere, and, if so, what are the dynamical processes? KEY MEASUREMENTS The key measurements that will answer the outstanding issues for these different classes of objects can be obtained by similar methods. For example, to answer questions about dynamics researchers need to determine the objects' orbits by tracking their motions precisely over months to years. To answer questions about the processes of accretion and erosion it is necessary to determine each object's size by making separate measurements of brightness and albedo. The degree of internal differentiation is indicated by studying the surface geology and measuring gravitational and magnetic fields of larger objects. The distribution of surface volatile ices is derived by combining

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Space Studies Board spectroscopic measurements and multispectral imaging. Stellar occultations of major bodies such as Pluto and Triton have provided rare opportunities to detect and study the vertical structure of their tenuous atmospheres. Characterization of the distribution of atmospheric hazes, clouds, and winds requires imaging from a spacecraft that passes close to the object. CONCLUSIONS AND RECOMMENDATIONS Three of the thematic rationales for the exploration of the trans-neptunian region (exploration of new territory, reservoirs of primitive materials, processes that reveal the solar system's origin and evolution) involve using methods that have proven successful in the past—telescopic observations, spacecraft missions, and harnessing new technologies and human ingenuity—to push the boundaries of our knowledge beyond 30 AU. Making links to extrasolar planet detection and studies of prebiotic chemistry will require planetary scientists to take interdisciplinary approaches and to venture with astronomers, chemists, and biologists into new fields of research. The main tasks for the next 10 to 15 years on the path to exploring the new frontier of planetary science in the distant outer solar system are to search for new objects and, more importantly, to document fully the chemical and physical makeup of the known bodies that constitute the trans-neptunian region. Spacecraft missions, telescopic observations, and research and analysis are the categories in which COMPLEX makes its highest-priority recommendations, as well as recommendations for augmenting this baseline effort. Spacecraft Missions To explore the makeup of objects in the trans-neptunian region, COMPLEX recommends an approach that combines telescopic observations of the bulk properties of a large sample of Kuiper Belt objects with close-up, spacecraft studies of the detailed properties of a few specific objects. The highest scientific priority for the exploration of the trans-neptunian solar system is extensive and detailed measurement of the fundamental physical and chemical properties of the Pluto-Charon system, end members of the KBO population. Since Pluto and Charon are barely spatially resolvable from Earth, many of the relevant properties can be measured only by robotic spacecraft. NASA's planning for a Pluto mission has undergone significant revision over the last few years. What was conceived of in the early 1990s as a Cassini-class mission requiring launch on a Titan-IV has been reformulated as a highly integrated spacecraft-payload combination capable of being launched on a Delta-II. The associated reduction in cost and the inclusion of a new start for a line of outer solar system missions in the administration's FY 1998 budget suggest that a Pluto mission is closer to realization than it has ever been since one was first conceived. Given Pluto's long rotation period (6.4 days) and the need for redundancy, COMPLEX recommends a dual spacecraft mission to Pluto. A single spacecraft would be able to observe only one hemisphere during its flyby. A second spacecraft would enable coverage of both hemispheres. Staggering the arrival times by, say, 6 months would also enable some retargeting of the second spacecraft based on results obtained during the first spacecraft's flyby. Augmentations Following a Pluto-Charon mission there are a number of future spacecraft projects that could be considered as part of a long-term program to explore the trans-neptunian solar system. These augmentations include: Adding a flyby of a Kuiper Belt object to a Pluto-Charon mission. The scientific potential of any PlutoCharon mission would be greatly enhanced by the spacecraft continuing on to visit another Kuiper Belt object and thus providing measurements of the size and surface characteristics of two different KBOs that have different histories. Locating a suitable KBO along the trajectory of a Pluto mission should be a priority goal for search programs. This augmentation should be considered only if it has no serious cost or schedule impact on a PlutoCharon mission. Conducting additional missions to Kuiper Belt objects. Objects in the trans-neptunian solar system are highly diverse, and the underlying causes for this diversity can be fully explored only by space missions. Scientific

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Space Studies Board gies. For one thing, some NASA Centers3 claim that their core competencies cover an extensive and broad range of technologies. No organization that has realistic fiscal constraints can hope to be competitive or world class across such a sweep. Modern industrial organizations are confining their core competency technologies to those that are key to their competitive survival and that are not available to be purchased at a lower cost on the outside. NASA should develop equivalent constructs for defining the core competencies of the Centers. NASA should recognize that when a technology important to its missions is available on the outside from either academic or industrial organizations, this fact represents a NASA success. In many cases NASA provided the vision and funding for that technology sometime in the past. NASA should now leverage that success and confine its core technologies to those needs that cannot be met better by outside developers. External review can assist NASA in defining its core competencies, but competitive results in terms of degree of innovation, advances in the state of the art, and impact on cost and performance will be the ultimate test of those competencies. Some of NASA's core competency groups are already world class and should be able to compete successfully with external groups for technology programs. Other areas may require some nurturing before achieving true core competency status. In such cases it may be necessary to target some limited ATD funds for this purpose, but a deadline should be set for accomplishing the objective, not to exceed 3 years. ATD funds should not be used more broadly to bolster in-house capability. A narrowing of core competencies to those that meet stringent criteria will mean that NASA personnel will not be the performers in all technologies that support the principal mission responsibilities of a particular Center. In the past, NASA has relied on the “smart-buyer” argument for maintaining many of these technology development activities even when they may have been available externally. Neither the concept of core technology nor NASA's budget constraints should be invoked simply to support the continuation of past practice. Further, there is ample evidence that there are alternatives to maintaining in-house, hands-on R& D programs that can be used to achieve smart buying. The variation in approaches used by agencies of the Department of Defense such as the Defense Advanced Research Projects Agency (DARPA), the National Reconnaissance Office (NRO), and the three military services demonstrates that there is no single avenue for procuring technology. Each agency, including NASA, can point to stunning successes (as well as unfortunate failures). The most appropriate strategy for maintaining the expertise needed to be a smart buyer can vary depending on the nature of the organization and its missions. Thus, NASA would do well to examine alternatives and develop an explicit strategy for remaining a smart buyer. Increasingly, successful approaches to acquiring the skills needed to be a smart buyer involve enhancements to workforce mobility. Increasing workforce mobility can improve organizational effectiveness in many ways, by facilitating the transfer of information, obtaining fresh points of view, and maintaining workforce expertise. Use of the Intergovernmental Personnel Act and cooperative agreements with outside organizations are options that NASA can use to support exchanges of technical staff. To be most successful, an ATD program should have its planning and execution involve a careful mix of centralized and decentralized activities, which, in NASA, means appropriate roles for headquarters and the Centers. Planning should be a headquarters-led effort with execution residing at the Centers. The 1995 NRC report made it clear that management of the technology selection process, including make-vs.-buy decisions, should be retained at headquarters. The selection process for near-term technologies for particular missions can be delegated to the Centers when they are not competing for the technology development activities. This division of responsibility is necessary to eliminate both perceived and real conflicts of interest. As NASA exits from non-core-competency technology execution, it should be possible to delegate more of the management and selection process to the Centers. Collecting cost data within NASA for analysis purposes is very difficult. Part of the difficulty is associated with NASA not operating on a full-cost basis. More important than analysis, however, is the problem that this lack presents to rational management decision making. NASA wholeheartedly agreed with the Managing the Space Sciences recommendation to move to full-cost accounting. Unfortunately, 3 years later NASA still states that it is a year or two away from the goal. The task group cannot emphasize too strongly the necessity, for NASA's own management purposes, to accomplish this task expeditiously. The task group was surprised, when conducting this review, that useful historical data were not readily available on such items as the breakdown of long- versus short-term research support, in-house versus academic versus industrial technology performance, and the amounts 3   To distinguish between NASA Centers (e.g., Ames Research Center or Goddard Space Flight Center) and NASA's centers of excellence, the former is capitalized (“Centers”), and the latter is referred to in lower case (“centers”).

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Space Studies Board competitively awarded. The task group hopes that when it shifts to a new accounting system, NASA will access, track, and use such information in the related planning process. Many of the recommendations of the above mentioned 1995 NRC report, as well as the present report, call for external review and advice. External review is recommended for the planning function, review of programs, evaluation of competing proposals, core competency selection, and Center quality review. Providing adequate headquarters staff to handle the reviews, utilizing clear investment and performance metrics, and making Centers accountable to headquarters are essential elements of the review process. Effectively implementing the review and advisory process depends on a synergistic relationship between NASA, academia, industry, and other government organizations that has, in large part, already been achieved and needs to be increased and maintained. It carries on a tradition that goes back to NASA 's predecessor organization, the National Advisory Committee for Aeronautics. Nevertheless, the final decision making is always a government responsibility, putting a premium on the quality of NASA's personnel. The task group hopes that the recommendations of this and the previous NRC report will assist in promoting excellence in all aspects of the nation 's space endeavors. To that end, NASA should make regular formal reports to appropriate external bodies on its response to the recommendations. REFERENCE National Research Council (NRC). 1995. Managing the Space Sciences. Space Studies Board and Aeronautics and Space Engineering Board. Committee on the Future of Space Science. National Academy Press, Washington, D.C.

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Space Studies Board 3.11 Ground-based Solar Research: An Assessment and Strategy for the Future A Report of the Task Group on Ground-based Solar Research1 EXECUTIVE SUMMARY Solar physics is a critical part of the nation's natural science program and a research area of fundamental importance to physics and astrophysics. The Sun is the only star that can be resolved in detail in its interior, on its surface, and in its outer atmosphere, thus making it an important and unique laboratory for fundamental physics, astrophysics, fluid mechanics, and magnetohydrodynamics. Further, the radiative and particle outputs of the Sun, and their variation, have a controlling influence on Earth's atmosphere, climate, and near-space environment. The field of stellar astrophysics would not include knowledge about starspots, prominences, differential rotation, flux tubes, flares, coronal mass ejections, tenuous supersonic winds, the nature of hot, dense X-ray coronal loops, or the variation of the total brightness of a star over years and decades without the discoveries of these phenomena on the Sun. Scientists understand the physics of these diverse phenomena only insofar as they have worked out the physics from studies of the Sun. In the broadest terms, it remains only partially understood why the Sun, or any other star, is obliged by the laws of physics to carry on the many curious phenomena that are collectively known as magnetic activity. In particular, the existence of a million-degree corona surrounding a 6,000-degree surface is not understood except in outline. This is a fundamental problem in the physics of stellar systems, and a solution is required if there is to be any confidence in the interpretation of X-ray and extreme-ultraviolet emission of astrophysical objects. The Sun is the only laboratory where these questions can be studied in some detail. This report reviews the scientific challenges posed by the active and variable Sun, and it is those challenges that drive the recommendations of the report. The general behavior of the major phenomenological components of solar activity are effectively pursued with the ongoing space program and existing and proposed ground-based telescopes. However, scientific understanding of the basic physics of these phenomena is stymied by an inability to resolve many aspects of the fundamental magnetic energy release processes that are occurring at scales of approximately 75 km or less. Clearer understanding requires observations with better than 0.1 arc-second (") resolution, but existing telescopes provide at best approximately 0.3" to 1.0" resolution. THE ROLE OF GROUND-BASED PROGRAMS IN SOLAR RESEARCH The activity of the Sun varies over years, decades, and centuries, evidently reflecting diverse internal magnetic and convective states. A number of the fundamental scientific challenges noted above require spatial and temporal resolution and long-term synoptic coverage that can only be realistically achieved through a program of ground-based observations. Ground-based solar research programs provide easy accessibility to facilities for the entire solar-physics community and are a means for the hands-on education of the next generation of solar researchers. They can be responsive to rapid intellectual, technical, or solar activity developments, as instrumentation on the ground is comparatively easy to repair, modify, calibrate, and replace. In addition, the costs of a ground-based facility are also typically far lower than those of space-based equivalents. Observations from space have opened up a new world unknown to and inaccessible from the ground, but ground-based observations are credited with the discovery of the Sun's cyclic magnetic activity, the million-degree temperature of the corona, the fine-scale, fibril state of the solar magnetic fields, and the surface pressure waves (p-modes). Further, ground-based observations provide the critical data required by the designers of space missions. Finally, ongoing nighttime observations of brightness and magnetic activity of distant solar-type stars are demonstrating the varying states of activity the Sun may have achieved in other centuries. These observations, combined with data on Earth's atmosphere, indicate that variations in the Sun's radiative and plasma emissions are capable of influencing the weather and climate at Earth's surface. 1   “Executive Summary” reprinted from Ground-based Solar Research: An Assessment and Strategy for the Future, National Academy Press, Washington, D.C., 1998, pp. 1-7.

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Space Studies Board The task group believes that the primary tasks of ground-based telescopic research should be the following: Obtaining a long-term synoptic record of solar activity: The National Solar Observatory, the High Altitude Observatory (HAO), and independent observatories—including, for example, Mt. Wilson, Stanford-Wilcox, Big Bear, San Fernando, and Marshall Space Flight Center—have an important role in this effort. Studying the solar interior and the generation of magnetic fields by mapping subsurface flows and interior magnetic fields through long-term helioseismological observations; and Observing the interaction of convection, magnetic fields, and radiative transfer by imaging with high spatial, temporal, and spectral resolution. THE CURRENT U.S. GROUND-BASED SOLAR RESEARCH PROGRAM For convenience, the task group divided its discussion of the current U.S. ground-based solar research program into (1) major solar observational facilities; (2) data, theory, and modeling; and (3) people, programs, and institutions—the means by which elements 1 and 2 are integrated to advance scientific understanding. Major Solar Observational Facilities The National Solar Observatory, a multisite facility of the National Optical Astronomy Observatories (NOAO), is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. The current responsibilities of the NSO include the following: Continued operation of the Kitt Peak (NSO/KP), Sacramento Peak (NSO/SP, “Sac Peak”), and Tucson facilities; Operation and upgrade of the multisited telescopes of the Global Oscillations Network Group (GONG) for continuous studies in helioseismology; Fabrication and operation of the SOLIS array for synoptic optical long-term investigation of the Sun; and Archiving and distribution of data, and providing specialist-supported access to NSO observing facilities. The NSO operates the two largest U.S. telescopes for ground-based solar observation—the McMath-Pierce telescope at Kitt Peak (commissioned in 1961) and the Vacuum Tower Telescope (VTT) at Sac Peak (commissioned in 1969). NSO facilities are available to both local staff and visiting scientists worldwide. To maximize scientific productivity, NSO policy provides for visiting observers to be assisted by experienced NSO staff. This support is unique among all other solar observatories worldwide and exemplifies the collaborative role of the NSO in the solar physics community. Although the task group's assessment of U.S. observatories focused on NSO facilities, important solar research facilities exist elsewhere. For example, vector magnetograms are recorded by the University of Hawaii's Mees Solar Observatory, California State University at Northridge's San Fernando Solar Observatory, NASA's Marshall Space Flight Center, and the New Jersey Institute of Technology's Big Bear Solar Observatory.2 Similarly, the Stanford University Wilcox Solar Observatory specializes in low-resolution magnetograms designed to show the current sheet separating the northern and southern magnetic hemispheres of the Sun and the large-scale surface velocity patterns. Facilities outside the NSO also provide data essential to supporting ongoing NSO programs. For example, data from the Mt. Wilson 60- and 150-foot solar tower telescopes complement data from GONG and other helioseismic experiments. Finally, U.S. solar radio observatories also are outside the NSO set of solar observation facilities. Solar observations in the radio part of the electromagnetic spectrum provide a unique perspective on phenomena in the solar atmosphere. Many excellent solar observing facilities also exist outside the United States, although none operates a wide range of well-documented instruments and also provides resident observers who aid in their operation. Nevertheless, the non-U.S. programs illustrate the worldwide interest in the active Sun and suggest the possibility of a 2   On July 1, 1997, the management of Big Bear Solar Observatory was transferred from the California Institute of Technology to the New Jersey Institute of Technology.

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Space Studies Board vigorous international collaborative effort should the United States choose to go forward with plans for the demonstration of adaptive optics and development of the Advanced Solar Telescope discussed in this report. The past decade of solar research has shown that spatial resolution of fractions of an arc-second and temporal resolution of a few seconds are required to characterize the interaction of solar magnetic fields and convective flows on the scales at which they actually occur. Further, the need for high sensitivity to magnetic fields necessitates an infrared observational capability out to wavelengths of approximately 15 microns. Operating at such long wavelengths with even minimally acceptable resolution requires a larger-aperture telescope than any that currently exists. No solar optical telescope operating today has the attributes needed to enable studies of the energy release processes that occur at very small scale sizes. In addition, addressing several of the fundamental solar science questions mentioned in this report would require upgrades to the capabilities of existing solar radio observatories. Data, Theory, and Modeling Studies of the Sun and its influence on the interplanetary and Earth environment often involve making correlations between various observed physical parameters. Achieving a readily usable and accessible data archive requires developing an easily searchable catalog of data, ensuring access to data through user-friendly software, and guaranteeing the ability to handle the large quantities of data now available and that are planned in the future. Such data archiving is essential to maintaining and providing ready access to already existing, ongoing, and future data sets. Several centers and institutions in the United States have, or will soon have, online images and other data available through the Internet. However, sifting through the vast quantities of data for observations of specific solar phenomena is often a formidable task without an intimate knowledge of a particular institution's archive structure or a catalog that goes beyond a simple list of the available data. As a result, several efforts are being advanced to provide a mechanism to identify and retrieve data from a large number of sources. Acknowledging the importance of providing data to the community, the task group encourages the cooperation and participation of observatories and institutions in efforts to archive and provide access to their data. Historically, many of the innovations that have led to new observational facilities have had their origins in small-scale university and institutional research. Although much of the current solar data analysis and theoretical work continues to be done in universities and national institutes with NSF funding, today an increasing amount of solar physics research is conducted at institutes and universities that focus more on space-based projects, with only indirect attention to ground-based studies supported by research and technology contracts from NASA. Thus, for example, the Big Bear Solar Observatory, the Lockheed Martin Solar and Astrophysics Laboratory, NASA's Marshall Space Flight Center, and others reflect the changing pattern away from research traditionally supported by NSF to research oriented toward space-based observations of the Sun for which there is support. New academic research groups at Michigan State University, California State University at Northridge, Montana State University, and the New Jersey Institute of Technology also reflect this trend. In addition to an adequate complement of supporting instruments, the success of the priority facility projects discussed in this report (SOLIS, the upgrade of GONG, and the Advanced Solar Telescope) rests on the availability of adequate funds for data analysis, modeling, and theoretical investigations. Plans for this intellectual infrastucture need to be incorporated at the start of new projects, as has been proposed for the Solar Magnetism Initiative, a multi-institutional proposal to the NSF for an integrated study of solar magnetism and variability. People, Programs, and Institutions The critical elements that enable the capacity of state-of-the-art observing systems and the potential of richly populated data collections to be translated into scientific understanding are people, programs, and institutions. That is, progress in science depends on being able to draw on a critical-mass-size research community (people) who, in turn, are supported by adequate intellectual and physical infrastructure (institutions). Specific programs can serve to integrate the contributions of various kinds of research (e.g., observations, theory, and modeling) and promote the synthesis of new perspectives on critical scientific problems. The task group notes the importance of a balanced NSF approach to facility development and scientific grant support for the optimum long-term handling of solar research. This requires NSF research grants for individual solar scientists in universities, institutes, and observatories, as well as active communication and coordination

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Space Studies Board between the major solar research centers (NSO and HAO), agencies (NSF, NASA, DOD, and NOAA), and the national infrastructure of universities, observatories, and institutes. The task group believes that the magnitude of the grants program for individual researchers should be commensurate with the funding of the centers. At present, there is a strong space-based solar research program that is able to analyze and interpret observational data effectively. Solar space research is conducted in university space science groups, NASA field centers, Department of Defense research laboratories, and some corporate research facilities. However, historically strong, university-based research groups that carry on ground-based solar research (for example, those at the California Institute of Technology, Stanford University, the University of Maryland, and the University of Colorado) are losing or have lost tenured solar faculty. Institutions such as the New Jersey Institute of Technology and Montana State University have stepped in with new faculty hires, but the task group remains concerned about the trend away from traditional ground-based solar research and the likely effect on training for the next generation of graduate students. The task group is also concerned about the current state of university-based instrumentation programs, which are widely seen as essential to future instrument development, as well as the reduced access of new researchers to hands-on observing experience. Existing instrumentation and training programs are few in number and rely on precarious grant-based funding. A STRATEGY TO STRENGTHEN GROUND-BASED SOLAR RESEARCH The task group believes that although there is great strength in the current ground-based solar research program, it is nevertheless fragile. Specifically, there is an urgent need to develop a coherent strategy for ground-based research that will address the following issues: Aging national facilities; Limited capabilities to pursue the most important scientific problems; Concerns about the health of the research community, especially in academia; and The need for a workable plan to effectively integrate the diverse pieces of ground-based solar research into a synergistic whole. The task group concluded that such a strategy can be built around the three elements mentioned above: (1) major observing facilities; (2) data, theory, and modeling; and (3) people, programs, and institutions. Within this strategy, the task group believes that the highest priority should be accorded to major observing facilities. This is so for several reasons. First, new observing facilities are required to address the major scientific questions in solar research. Second, new facilities are needed to replace certain of the aging facilities now in operation. Third, but especially importantly, major new facilities will constitute the most effective way to attract and engage the next generation of outstanding researchers who will bring vigor and momentum to ground-based solar research in the United States. Recommendations Regarding Facilities The following four recommendations are presented in priority order. Recommendation 1: Complete fabrication of the SOLIS facility over the next 3 years, operate it at an appropriate site, and provide funding for U.S. scientists for data analyses. Recommendation 2: Upgrade the GONG system by installing appropriate 1024 × 1024 CCD sensors, and operate GONG over a whole solar cycle with funding for data analysis in the United States. Recommendation 3: Develop, construct, and operate a 3- to 4-meter Advanced Solar Telescope (AST). The AST might also be called the “Solar Microscope” because it would, for the first time, peer into the mysterious world of the active magnetic microstructure. Work toward the AST by:

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Space Studies Board Strengthening the NSO adaptive optics program immediately, including an augmentation in funding of approximately $1.5 million for the next fiscal year; Demonstrating the required adaptive optics (0.1" or better resolution in visible light at 0.5 microns) on a telescope with an aperture of approximately 1.0 to 1.5 meters; Beginning preliminary design of the 3- to 4-m AST so as to be ready for the final design when the adaptive optics has been convincingly demonstrated; and Carrying on site testing to determine an accessible site with the best available seeing as quickly as possible so as to define the task for the adaptive optics and be ready for construction of the AST. Recommendation 4: Begin exploratory development of a high-resolution, frequency-agile solar radio telescope (FASR), using existing radio observatories to demonstrate its scientific potential. The FASR would provide unique diagnostics of solar flare plasmas, detect and locate the myriads of microflares, and provide maps of magnetic fields over surfaces of constant density within active regions. Recommendations Regarding Data, People, Programs, and Institutions The four recommendations above relate to priority actions for major observing facilities. The next set of recommendations focuses on addressing the issues that emerge in the two other major elements of the U.S. ground-based solar research program, which are (1) data, theory, and modeling and (2) people, programs, and institutions. Unlike the recommendations on facilities, they are not presented in priority order. Recommendation 5: Facilitate efficient and timely development and utilization of the AST through enhancements to the management and organization of the NSO. Recommendation 5a: Consolidate the NSO science, engineering, and operations site when the AST is operational. Recommendation 5b: Establish an independent management council of the NOAO management organization to represent solar research, thereby recognizing the unique requirements for a program in ground-based studies of the Sun and placing such a program on an equal footing with the other major initiatives of NOAO. Recommendation 5c: Establish an advisory committee to the NSO director that would include leading solar physicists from NSO, HAO, universities, NASA, DOD, NOAA, and U.S. and international research partners. Recommendation 5d: Foster communication within the solar physics community by considering creation of an NSO national fellowship program, perhaps structured along the lines of the visiting scientist program that has been in place for many years at HAO. Recommendation 6: Establish the essential national infrastructure for the effective operation and scientific exploitation of the U.S. solar observing facilities. Recommendation 7: Develop a collaborative NSF and NASA distributed data archive with access through the World Wide Web.

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Space Studies Board 3.12 Failed Stars and Super Planets: A Report Based on the January 1998 Workshop on Substellar-Mass Objects A Report of the Steering Group for the Workshop on Substellar-Mass Objects1 EXECUTIVE SUMMARY The first direct observation of a bona fide brown dwarf, Gliese 229B in 1995, coupled with the indirect detections of a number of objects of jovian mass or larger, has brought the study of substellar-mass objects (hereafter SMOs) into a new phase of observational investigations. This success, after many years of failed searches and false alarms, is a consequence of the advent of new detectors, refinement of long-standing observing techniques through the use of novel technologies and data-processing schemes, and the persistence of searchers. Observational successes have been mirrored by advances in the theoretical modeling of both the spectra and the structure and evolution of SMOs. Developments in theoretical understanding of SMOs have been enabled by more capable computers, new laboratory data on the properties of materials at high pressure, and the stimulus of discoveries of actual objects. These advances have coincided with, and reinforced, increasing public and NASA interest in the broader issue of how unique our own planetary system is, the likelihood of life elsewhere, and what is required to make discoveries that will answer these questions. Although the intellectual linkage between study of SMOs and the question of the frequency of planetary systems is a firm one, for various programmatic reasons the future investigation of SMOs with both ground-and space-based telescopes has not been well thought through to date. Past reports from the National Research Council's (NRC's) Committee on Planetary and Lunar Exploration (COMPLEX) and NASA advisory groups on the detection and study of extrasolar planets have concentrated primarily on the study of SMOs as the first step toward detecting Earthlike planets around other stars, the ultimate programmatic goal of NASA's new “Origins” initiative. Comparatively less attention has been given to the intrinsic value of studies of SMOs for answering high-priority questions in astronomy and planetary science, including those related to the physics of star and planet formation, the abundance of luminous and dark matter throughout the cosmos, and the basic physics of matter under extreme conditions. The recently demonstrated ability to observe and study SMOs is significant for reasons additional to and unconnected with extrasolar planets. The eventual determination of the abundance of low-luminosity, low-mass objects will place constraints on models of the nature of the dark matter on astrophysical scales ranging from the solar neighborhood through the cosmological both directly (in terms of the contribution of SMOs) and indirectly through their constraints on the stellar initial-mass function. The local SMO contribution is starting to be constrained by sensitive surveys of the Sun's galactic neighborhood to determine directly the abundance of such objects as free-floaters, companions, and cluster members. Attempts to determine the galactic and extragalactic mass contribution of SMOs by detecting their gravitational-lensing effect on background stars have been under way for several years and are beginning to yield constraints. THE WORKSHOP ON SUBSTELLAR-MASS OBJECTS Given the recent successes in discovering SMOs by direct and indirect means, and the shared interest in them by research communities with very different goals and perspectives, the Space Studies Board organized a workshop to conduct a systematic cross-disciplinary examination of the state of the field. Its purpose was to assess the current state of the field and identify future studies that might contribute to important research goals in star and planet formation, the frequency of planetary systems, the nature of non-luminous matter on scales up through cosmological, the behavior of matter under extreme conditions, and the evolution of atmospheres of objects ranging in mass from planetary through stellar. The state of the field as summarized at the workshop by 21 invited experts is vigorous: substellar-mass objects are now being detected or characterized, on a regular basis, by roughly a half dozen different techniques, both 1   “Executive Summary” reprinted from Failed Stars and Super Planets: A Report Based on the January 1998 Workshop on Substellar-Mass Objects, National Academy Press, Washington, D.C., 1998, pp. 1-5.

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Space Studies Board ground- and space-based, with additional approaches nearing the maturity necessary to conduct successful searches. Much of the activity is a result of individual or small-team, principal-investigator-based, projects, rather than large-scale “mission-type” programs, although some of the discoveries have been made with instruments (e.g., the Hubble Space Telescope and Keck telescope) that are the result of large-scale public or private programs. Additional to the availability of large or space-based telescopes are the maturation and ready availability of sensitive detector systems. However, a substantial ingredient in the success of the searches is the invention of novel data-processing schemes (in turn enabled by high-speed and high-capacity computers), calibration techniques (such as the iodine cell utilized in the radial-velocity program), and the autocatalytic growth of observing networks linked by electronic mail and able to confirm transient events (e.g., microlensing networks). Powerful computers also have allowed modeling efforts to move from highly approximate schemes to capabilities more in line with the new data available. In particular, frequency-averaged or “gray” model atmospheres have given way to fully frequency-dependent models, handling tens of millions of spectral lines, essential both for synthesizing spectra to compare with data and for properly characterizing atmospheric energy balance. The discovery of a cohort of Jupiter-mass planets in close orbits around their parent stars has stimulated more elaborate hydrodynamical models of SMO formation, again enabled by high-speed computers. Because SMO interiors are under high pressure and (except for the most massive or youngest objects) moderately degenerate, the behavior of matter under extreme conditions is a crucial issue in understanding the formation and evolution of these bodies. Theoretical and experimental advances in high-pressure physics have led to improved characterization of the physical properties of SMOs. FINDINGS As a result of the presentations and discussions at the workshop and subsequent deliberations, the Steering Group for the Workshop on Substellar-Mass Objects formulated a number of findings about the current state of research related to SMOs. These findings are organized under headings related to the five questions posed in NASA 's request for an examination of pertinent issues (see preface). Status of Current Research Activities The study of SMOs is currently in a state of high vigor after several decades of false starts and frustrations. The key to the new successes lies in technological advancements in ground-based telescopes buttressed by results from key spacecraft programs and theoretical studies of growing power and fidelity. The challenge for NASA and other funding agencies is to foster these programs in such a way that they contribute to NASA's ultimate programmatic goal of discovering terrestrial planets in orbit around other stars, but without encouraging a premature narrowing of focus toward a single, high-cost technique or mission. The Most Compelling Issues for Near-Term Study Investigations of SMOs are still in their infancy. The number of known brown dwarfs and extrasolar giant planets is still relatively small and provides an insufficient basis for drawing definitive conclusions about the range of properties exhibited by these objects. Detailed information on the properties of most SMOs is still lacking. Thus the most compelling issues to be addressed in the near term are the following: Devising detection strategies to increase the population of known SMOs beyond the several hundred expected from the Deep Infrared Survey of the Southern Sky (DENIS) and the 2-Micron All-Sky Survey (2MASS) and, thus, increase the extent of SMO parameter space accessible for study; and Performing spectroscopic and other diagnostic studies to characterize individual, nearby SMOs. In the first of these, the ground-based radial-velocity surveys that have moved to the new generation of large-aperture telescopes, coupled with the continued development of astrometry, will increase the sample size of SMOs by an order of magnitude. The next phase is to use space-based facilities to undertake measurements not possible from Earth. The Space Interferometry Mission (SIM) and the Kepler photometric mission both represent efforts in this direction.

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Space Studies Board A balanced program that fully explores as much as possible of the relevant parameter space is essential. In particular, to advance SMO studies in the near term and to optimize the development of space-based facilities, NASA must balance its major space expenditures with adequate funding for the early steps involving ground-based techniques and flight demonstrations. For characterizing individual objects, the technique of choice will continue to be spectroscopic studies. The technologies needed to probe the spectra of SMO candidates have direct application to the goal of acquiring the spectra of terrestrial planets around nearby stars using space-based telescopes. However, the continued advancement of SMO studies requires that NASA encourage a range of approaches that will have broad scientific benefit for the detection and characterization of SMOs. Success in this effort will have the additional benefit of providing the potential for alternative and unexpected solutions to the problem of characterizing extrasolar terrestrial planets. Close-in orbit companions such as 51 Pegasi B may not be amenable to spectroscopic study in the foreseeable future. Multiple techniques, including astrometry and detection of broadband reflected light, will need to be applied to understand the nature of these objects. Contributions to Broader Scientific Goals SMOs are a bridge between stars and planets, in that the physics of their atmospheres and interiors represents a genuine transition from stellar physics to planetary physics. Moreover, the ability to model the structure, evolution, and appearance of SMOs represents an important test of basic physics in a little-explored range of parameter space. In addition to greatly improving current understanding of the general theory of star and planet formation, studies of SMOs are likely to contribute to broader scientific goals in areas such as those represented by the following three compelling examples: Modeling the atmospheres and interiors of SMOs; Testing models of the formation of SMOs; and Understanding the stability and evolution of multiplanet systems. To advance these areas requires that: Laboratory and associated computational efforts be undertaken to construct accurate spectral-line lists; Parallel, vector, or superscalar processors become widely available so that theoretical models can take full advantage of current understanding of the physics of SMOs; Larger telescopes and more sensitive detectors be brought to bear on characterizing brown dwarfs; Experimental and theoretical studies of the behavior of materials at high pressure continue to be supported and to increase in capability; and A broad range of observational strategies for detection (i.e., astrometric, photometric, radial-velocity, and microlensing studies) and characterization (e.g., spectroscopic studies over a broad range of the electromagnetic spectrum) of SMOs be undertaken to ensure that the sample space of these objects is large enough to generalize the frequency and mechanisms of formation. Opportunities for Interdisciplinary Research The Contribution of Studies of SMOs to Achieving Long-Term Scientific Priorities The study of SMOs is necessarily interdisciplinary in nature, and progress in this field will require planetary scientists and astronomers to communicate and collaborate with each other as well as with colleagues from across a broad range of disciplines in the physical sciences. Studies of SMOs have direct relevance to a number of long-standing scientific goals and priorities, their most obvious role being to provide a testing ground for honing the instrumentation and observational techniques necessary to detect extrasolar terrestrial planets. Another key area is the contribution of SMO studies to constraining the identification of missing mass in the universe. Although it appears that SMOs do not constitute the

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Space Studies Board bulk of the matter in the universe, they represent unique probes of galactic structure. Observations of microlensing events have particular promise for probing the mass function of brown dwarfs and understanding the composition of the galactic halo. With appropriate developments, microlensing could provide a shortcut to the detection of extrasolar terrestrial planets. To ensure continued progress in this area, NASA and other agencies should foster coordination and collaboration among various search programs to enable ongoing discoveries and to follow up on possible candidate events. Because microlensing groups have different primary goals, the various agencies supporting primary and follow-up microlensing observations should work together to minimize potential disruptions caused by differences in their prime goals. Measurement of higher-order microlensing events is required to determine the sources of lens effects in some cases. The reflex motion resulting from Earth's orbit around the Sun, for example, causes the trajectory of the background star relative to the lensing object to deviate from a straight line. This parallax effect induces asymmetries in the light curve of microlensing events which should be of order 1% if the lenses lie in the halo, but negligibly small if the lenses are in the Large Magellanic Cloud. Thus, a search for parallax asymmetries as an adjunct to the microlensing program will yield additional important information on the nature of the objects creating the lensing events. CONCLUDING REMARKS The ultimate programmatic goal of NASA's Origins program—discovering another Earth—is a laudable one upon which no specific recommendation is laid. In addressing this goal, however, NASA should take the following actions: Continually assess the new information that studies of SMOs are providing on the formation, frequency, and characteristics of planetary systems, and invest judiciously in developing observational and theoretical techniques that will foster new discoveries. This investment should be in addition to the funding NASA is already providing for technological development of future large projects such as the Space Interferometry Mission and the Terrestrial Planet Finder. The funding must be flexible and peer-reviewed in recognition of the nature of the activities, which are distributed, principal-investigator-based projects to observe and model SMOs by using a variety of different approaches. The small-scale nature of these activities suggests that existing procedures (e.g., periodic peer review of proposals and resulting publications) will be adequate to identify and prioritize the approaches and techniques deserving of additional investment. Invest with care in select ground-based facilities, instrument, and computational programs that will significantly broaden the near-term opportunity for innovation in the identification and characterization of SMOs. Addressing the broader issue of the appropriate balance of support for ground-based programs among NASA, the National Science Foundation, and other appropriate agencies is beyond the scope of this report. This important topic is best addressed by the decadal survey committee in the context of the findings of the study on the federal funding of astronomical research currently being conducted by the NRC's Committee on Astronomy and Astrophysics. Consult with other agencies (e.g., the National Science Foundation) to avoid duplication and to open a broader set of opportunities for research and discovery through cooperative or collaborative funding. In sum, SMO research is at the heart of trying to understand the matter content of the universe, the ubiquity and properties of planetary systems, and the relationship (in both genesis and physical properties) between stars and objects not massive enough to ever become stars. By studying SMOs we extend our understanding of the cosmos from the ubiquitous macroscale of stars through to the planets and, hence, ever closer to the human realm.