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NASA: A Knowledge Agency
INTRODUCTION
The mission of the National Aeronautics and Space Administration (NASA) is—
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To advance and communicate scientific knowledge and understanding of the Earth, the solar system, and the universe.
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To advance human exploration, use, and development of space.
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To research, develop, verify, and transfer advanced aeronautics and space technologies.1
NASA’s program is divided into five strategic enterprises: (1) Aerospace Technology, (2) Biological and Physical Research, (3) Earth Science, (4) Human Exploration and Development of Space, and (5) Space Science.2 This report is concerned with the Earth Science and Space Science Enterprises. Both enterprises collect large volumes of data from spaceborne instruments, either to study changes in the oceans, atmosphere, and land surface of the Earth or to explore the universe and search for life beyond the Earth. Managing the data collected from these missions in order to further scientific understanding now and in the future is an enormous challenge.
The Task Group on the Usefulness and Availability of NASA’s Space Mission Data was charged by NASA’s associate administrators for earth science and space science to (1) evaluate the availability and accessibility of data from earth and space science missions, (2) determine the usefulness of NASA’s data collections for supporting scientific studies, and (3) assess whether the balance between attention to mission planning and implementation versus data analysis and utilization is appropriate. (The complete charge is presented in Appendix A.) This report reviews the data systems, services, and strategies for managing earth and space science data collected from space. (The stages in collecting data, from planning a mission to long-term maintenance of data, are described in Appendix B.) Chapter 1 explores the goals of several of the earth and space science disciplines that rely on NASA missions, and it describes how data are used to achieve important science objectives. Chapter 2 describes how the data are currently managed and evaluates the effectiveness of these management strategies. The focus is on the 16 major data facilities and data services that have significant holdings (e.g., at least 1 terabyte) or budgets (e.g., more than $1 million), or are intended to operate for many years. The major data facilities include active archives, which hold data that are being used intensively for research, and data centers, which maintain data that will continue to be used in the future. (Information asked of
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National Aeronautics and Space Administration, 2000, NASA 2000 Strategic Plan, Washington, D.C., 72 pp. |
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See <http://www.nasa.gov >. |
these facilities in a questionnaire is listed in Appendix C.) The satisfaction of the users, who ultimately judge the success of the system, is discussed in Chapter 3. Chapter 4 then examines some new approaches for increasing the availability and usefulness of earth and space science data, discusses the balance between mission operations and data analysis, and makes some recommendations about how to meet the data challenges of the next decade. Background information, including biographical information on task group members (Appendix D), meeting agendas (Appendix E), and an acronym list (Appendix F) appear at the end of the report.
SPACE SCIENCE ENTERPRISE
The science objectives of NASA’s Space Science Enterprise are to “solve mysteries of the universe, explore the solar system, discover planets around other stars, search for life beyond Earth from origins to destiny, chart the evolution of the universe and understand its galaxies, stars, planets, and life.”3 The Space Science Enterprise, managed by the Office of Space Science (OSS), is divided into four science themes: (1) origins, which seeks to understand where we come from and whether we are alone; (2) the structure and evolution of the universe; (3) the Sun-Earth connection; and (4) solar system exploration. Examples of the science programs and their interactions with data sets are described below.
Astrophysics: Origins and the Structure and Evolution of the Universe
NASA missions have opened up new windows on the universe, vastly increasing our knowledge about the world around us. Astrophysical sources, collectively, radiate across the spectrum: from gamma rays and X-rays, through the visible and infrared, all the way to microwaves and long-wavelength radio waves. Much of this radiation does not penetrate the Earth’s atmosphere and can be studied only from space. NASA’s scientific priorities for future missions, developed in coordination with the research community,4 include:
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Understand the structure of the universe, from its earliest beginnings to its ultimate fate;
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Explore the ultimate limits of gravity and energy in the universe;
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Learn how galaxies, stars, and planets form, interact, and evolve.5
Even modest success in achieving these goals would constitute a spectacular advance in human understanding, and NASA has become an acknowledged leader in this exciting venture. The program seeks to address “the most fundamental questions that science can ask: how the universe began and is changing, what are the past and future of humanity, and whether we are alone. In taking up these questions, researchers and the general public—for we are all seekers in this quest—will draw upon all areas of science and the technical arts.”6
The goals outlined above require that data be accessible in a form useful to the science community, that is, calibrated and maintained in accessible data facilities, along with tools for analyzing and visualizing the data. As stated in the 2000 OSS Strategic Plan:
Vast amounts of data are returned from space science missions. The volume, richness and complexity of the data, as well as the need to integrate and correlate data from multiple missions into a larger context for analysis and understanding, present growing opportunities. Exploration and discovery using widely distributed, multi-terabyte databases will challenge all aspects of data management and rely heavily on the most advanced analysis and visualization tools. The design and implementation of the next generation of information systems will depend on close collaboration between space science and computer science and technology.7
To achieve its objectives, NASA is flying or plans to fly an ambitious suite of missions (see Table 1.1), with still more to come (e.g., Next Generation Space Telescope, Space Interferometry Mission, and Constellation X). The missions illustrate the diversity of fields that will contribute to the goals of the strategic plan (cosmic rays, nature of high-energy sources, star formation in galaxies, dark matter, cosmology). The diversity of the science and the associated experimental approach lead to a wide range in types of data (time-tagged event logging, multispectral images, and spectroscopy, among others), and each data set and its archive will naturally have different characteristics and requirements.
With the launch of new missions, the volume of astrophysics data will increase substantially, and the demand to compile federated data sets—that is, data sets that can be accessed, intercompared, and queried simultaneously—from different missions will increase. For example, the Galaxy Evolution Explorer (GALEX) is designed to measure the ultraviolet light emitted directly from populations of hot, young stars in galaxies. Some of this ultraviolet light is absorbed by dust grains in interstellar space in the galaxies and is re-emitted as infrared radiation. One of the goals of the Space Infrared Telescope Facility (SIRTF) is to measure that reradiated energy. Thus, a combination of GALEX and SIRTF observations is needed to obtain a comprehensive picture of the cycling of interstellar gas through stars. That information, in turn, is needed to achieve an understanding of how galaxies were formed and how they have evolved. It is clear that the science will require databases that facilitate combining not just GALEX and SIRTF data, but data from other ultraviolet and infrared missions as well as data at other wavelengths.
The Hubble Space Telescope (HST) is one of the most powerful tools ever built for astronomy, and it continues to produce spectacular results. Several generations of instruments on HST will have been deployed during its expected 20-year lifetime. Data are calibrated and held by the Space Telescope Science Institute (see Chapter 2), along with data from several other past and current missions and ground-based surveys. With the accumulation of new observations, research based on mining the HST active archives—often for studies quite different from those originally conceived—has increased at a rapid rate. Archival research now accounts for a substantial fraction of all HST research. Data are now retrieved from the HST active archive at a rate four times higher than that at which new data are put into the archive (see Figure 1.1).
The growing number of data sets from diverse missions makes it possible to tackle important scientific problems in new ways, both by combining measurements from different missions and by taking advantage of the time baselines covered by the data (see Box 1.1).
TABLE 1.1 Selected U.S.-Led Astrophysics Missions
Mission |
Objective |
Current Missions |
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Chandra X-ray Observatory (CXO) |
Observes X-rays from high-energy regions of the universe, such as the remnants of exploding stars. |
Far-Ultraviolet Spectroscopic Explorer (FUSE) |
Explores the universe using high-resolution spectroscopy in the far-ultraviolet spectral region. |
High Energy Transient Explorer 2 (HETE-2) |
Detects and localizes gamma-ray bursts. |
Hubble Space Telescope (HST) |
Provides detailed images of celestial objects at high resolution. |
Microwave Anisotropy Probe (MAP) |
Measures the temperature of the cosmic background radiation over the full sky. |
Submillimeter Wave Astronomy Satellite (SWAS) |
Measures the amount of water, molecular oxygen, carbon monoxide, and atomic carbon in interstellar clouds. |
Upcoming Missions |
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Advanced Cosmic Ray Composition Experiment for the Space Station (ACCESS) |
Study cosmic rays of very high energy to understand elementary particles in our galaxy. |
Galaxy Evolution Explorer (GALEX) |
Measure the ultraviolet light emitted directly from populations of hot, young stars in galaxies. |
Space Infrared Telescope Facility (SIRTF) |
Measure astrophysical phenomena at infrared wavelengths. |
Swift Gamma Ray Burst Explorer (Swift) |
Discover, detect, and study gamma-ray bursts. |
BOX 1.1 Importance of Astrophysics Archives Examples of the role of NASA’s astrophysics archives in advancing knowledge include the following:
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The Sun-Earth Connection
The “Sun-Earth Connection” is the name given to a broad NASA program that includes studies of the Sun, the processes that link the Sun to the Earth, and the space environments and upper atmospheres of other solar system bodies. Another area of study characterizes the properties of the solar wind as it moves through the solar system. The overall goal of the program is to understand how and why the Sun varies and how the Earth and other planets respond to those variations.
The Sun’s energy output varies on timescales from seconds to billions of years. This energy reaches the Earth in two forms: as electromagnetic radiation and charged atomic particles. The Earth responds to the Sun’s varying energy inputs in a number of ways. Growing evidence indicates that even small variations in the total energy emitted by the Sun can alter circulation in the Earth’s atmosphere and hence affect climate (e.g., the Maunder minimum in solar activity, which is associated with a little ice age in Europe in the 17th century). Ejections of mass from the corona, which are more frequent near the peak of the solar cycle, cause auroras and disturb the Earth’s ionosphere in such a way as to disrupt communications, disable power grids, and damage satellites and alter their orbits.
In order to explore the effect of the Sun on the Earth, NASA is developing a series of missions that will characterize the solar energy output and the mechanisms that control it; explore the Earth’s space environment; compare the space environment of the Earth with that of other planets; and assess the impact of space weather on humanity. Many of these investigations will require access to archived data (see Box 1.2). A sampling of solar physics missions is listed in Table 1.2.
Solar System Exploration
NASA’s planetary exploration program is focused on answering fundamental questions about how planets form, why they are different from one another, and what conditions lead to the development of life. The last half of the 20th century was an extraordinary age of exploration and discovery. All of the planets in our solar system except Pluto have now been visited by NASA spacecraft. Each has been transformed from a remote astronomical object into a unique world, clearly distinct from all of the other objects in the solar system. Comparative planetology can provide real clues as to how the Earth itself and its habitability will be affected by changes in the total energy output of the Sun, climate change, increasing abundance of greenhouse gases, asteroid impacts, and so on.
Planetary research has been one of the primary beneficiaries of the recent change in NASA philosophy to support a diverse set of missions of moderate scale. Flight opportunities have become more frequent; several comets and asteroids, in addition to the major planets, have now been visited and characterized; and the advent of modern detectors has greatly increased the volume of data from each mission. Table 1.3 presents a sampling of planetary missions.
BOX 1.2 Importance of Archives for Solar and Space Physics Following are examples of the role of NASA archives in advancing solar and space physics:
SOURCE: Frank Hill, National Solar Observatory. |
TABLE 1.2 Selected Solar and Space Physics Missions
Mission |
Objective |
Current Missions |
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Advanced Composition Explorer (ACE) |
Samples low-energy particles of solar origin and high-energy galactic particles, and provides near-real-time solar wind information. |
Fast Auroral Snapshot Explorer (FAST) |
Probes the physical processes that produce auroras. |
Genesis |
Collects particles of the solar wind and returns them to Earth. |
Imager for Magnetopause-to-Aurora Global |
Exploration (IMAGE) Produces the first comprehensive global images of the plasma populations in the inner magnetosphere. |
Interplanetary Monitoring Platform 8 (IMP-8) |
Measures the magnetic fields, plasmas, and energetic charged particles of the Earth’s magnetotail and magnetosheath and of the near-Earth solar wind. |
International Solar Terrestrial Physics Global Geospace Science Program Polar (Polar) |
Images the aurora and measures the fluxes of charged particles and ions, magnetic and electric fields, and electromagnetic waves over the poles. |
Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) |
Studies the composition of local interstellar matter and solar material and the transport of magnetospheric charged particles into the Earth’s atmosphere. |
Solar and Heliospheric Observatory (SOHO) |
Studies the internal structure of the Sun, its outer atmosphere, and the origin of the solar wind. |
Stardust |
Collects dust from a comet’s nucleus. |
Transition Region and Coronal Explorer (TRACE) |
Images the solar corona and transition region. |
Ulysses |
Explores interplanetary space at high solar latitudes. |
Voyager Interstellar Mission (VIM) |
Searches for the heliopause boundary, the outer limits of the Sun’s magnetic field, and the outward flow of the solar wind. |
International Solar Terrestrial Physics Global Geospace Science Program Wind (Wind) |
Samples the upstream interplanetary medium, a principal region of geospace where energy and momentum are transported and stored. |
Future Mission |
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Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) |
Provide a new capability for stereoscopically imaging the magnetosphere. |
TABLE 1.3 Selected U.S.-led Planetary Missions
Mission |
Objective |
Current Missions |
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Cassini |
Makes observations of Jupiter and its moons (atmospheric dynamics and composition, Jupiter’s magnetic environment, the interactions between Jupiter and its moons) on its way to Saturn. |
Galileo |
Studies Jupiter and its moons in more detail than any previous spacecraft. |
Mars Global Surveyor (MGS) |
Measures surface features, atmosphere, and magnetic properties of Mars. |
2001 Mars Odyssey |
Maps the amount and distribution of chemical elements and minerals that make up the Martian surface. |
Future Missions |
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Mars Exploration Rover |
Analyze rocks and soils for evidence of liquid water that may have been present in Mars’s past. |
Mars Express |
Explore the atmosphere, structure, and geology of Mars to search for subsurface water from orbit and deliver a lander to the Martian surface. |
Comet Nucleus Tour (CONTOUR) |
Image two comet nuclei, and collect and analyze dust to reveal the comet’s composition. |
EARTH SCIENCE ENTERPRISE
Characterize, understand, and predict—these are the themes of NASA’s Earth Science Enterprise (ESE). The goal is “to develop a scientific understanding of the Earth system and its response to natural or human-induced changes to enable improved prediction capability for climate, weather, and natural hazards.”8 The research program is organized around a set of scientific questions aimed at understanding how the Earth is changing and the consequences of those changes for life on Earth.9 Some of the questions being addressed by the ESE program are as follows:
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How is the global Earth system changing?
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What are the primary causes of change in the Earth system?
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How does the Earth system respond to natural and human-induced changes?
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What are the consequences of change in the Earth system for human civilization?
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How well can we predict future changes in the Earth system?10
In order to answer these questions, the Earth Science Enterprise is currently conducting research in the following areas:
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Oceans and ice in the climate system;
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Biology and biogeochemistry of ecosystems and the global carbon cycle;
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Atmospheric chemistry, aerosols, and solar radiation;
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Global water cycle; and
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Solid Earth science.
These research topics also address major subproblems of the U.S. Global Change Research Program11 to which a space-based observational system is uniquely capable of making a significant contribution.12 Current and upcoming ESE missions are listed in Table 1.4.
Space-based data collected by the ESE address three classes of problems: (1) characterization of physical and biological processes, (2) monitoring status and changes, and (3) analysis of feedback mechanisms. “Characterizing and understanding a process” involves measurements to examine a specific process that operates in the Earth system, with the aim of developing physical models and model parameterizations. An example of this type of mission is the Tropical Rainfall Measurement Mission (TRMM),13 which measures the spatial and temporal variations in the tropical region (−35° to 35° latitude). The goals of this three-year mission are to study the frequency distributions of rainfall intensity and areal coverage and to relate the timing of heaviest rainfall to such factors as the nocturnal intensification of large mesoscale convective systems over the oceans and the diurnal intensification of orographically and sea-breeze-forced systems over land. TRMM data will potentially improve estimates of latent heating,14 which in turn will improve the prediction of rainfall events from global climate models. Recent results from TRMM, for example, show that windblown desert dust can choke rain clouds, cutting rainfall hundreds of miles away.15
Many of the instruments developed by the NASA ESE are used for systematic monitoring. An example of this class of instrument is the Total Ozone Mapping Spectrometer (TOMS).16 This class of instrument has been flown in four spacecraft with data extending back to November 1978 and has been used to monitor the amount of stratospheric ozone. A major result from the use of this and other instruments was the discovery of the growth of the Southern Hemisphere Ozone Hole,17 which led to the nearly worldwide phasing out of the use of the chlorofluoro-
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The U.S. Global Change Research Program was established in 1989 to develop and coordinate a research program to understand, assess, predict, and respond to natural and human-induced global change. Nine federal agencies, including NASA, and the Executive Offices of the President participate in the program. See Subcommittee on Global Change Research, Our Changing Planet, The FY2002 U.S. Global Change Research Program, Washington, D.C., 74 pp. |
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National Research Council, 2000, Review of NASA’s Earth Science Enterprise Research Strategy for 2000– 2010, National Research Council, Washington, D.C., 33 pp. |
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See <http://trmm.gsfc.nasa.gov>. |
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Energy from the Sun is stored in the form of water vapor. Condensation of water vapor in clouds releases this latent heat, causing the atmosphere to warm locally. |
15 |
See <http://www.gsfc.nasa.gov/gsfc/earth/dust/rainfall.htm>. |
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17 |
The loss of ozone was first detected by the British Antarctic Survey, which was monitoring the atmosphere using a network of ground-based instruments. The TOMS data confirmed that the ozone loss was real and that it extended over most of the Antarctic continent. See G.Carver, 1988, The ozone hole tour, Part 1. The history behind the ozone hole, University of Cambridge, <http://www.atm.ch.cam.ac.uk/tour/part1.html>. |
carbons (CFCs).18 The history of the total ozone measurements is composed of results from multiple instruments flown on different spacecraft; consequently, calibration between the results from these different instruments is critical to understanding the long-term evolution of total ozone. More importantly, new data are needed to determine if the mitigation steps (i.e., reducing the amount of CFCs released into the atmosphere) are effective. By their nature, long-term monitoring programs need to be able to relate measurements from different instruments, and the original data need to be available so that improved calibration and reduction algorithms can be applied.
The final category of problem—analysis of feedback mechanisms—is the most challenging for any data system, because understanding cause and effect requires comparison of different data sets collected from different satellites with different types of instruments. One of the fundamental questions to be addressed in this class of problem is the role that clouds play in relation to the effects of increasing carbon dioxide and other greenhouse gases. Clouds both reflect sunlight (which cools the Earth) and trap heat in the same way as greenhouse gases (thus warming the Earth). Different types of clouds do more of one than the other. The net effect of clouds on climate change depends on which cloud types change, and whether they become more or less abundant, thicker or thinner, and higher or lower in altitude.19 Different instruments measure different characteristics of the clouds, and determination of the full impact of clouds requires that these measurements be merged. Understanding of the evolution of cloud-type cover, how cloud types are being affected by climate change, and how they in turn affect climate change requires access to long-time histories of space-based and ground data and the ability to apply new algorithms to original data to extract data relevant to cloud types. This type of synthesis of results is the most challenging for any data system, but it is also the area where the most significant results from the NASA ESE are likely to come.
Many of the important science questions being addressed by NASA investigators require long-term, continuous measurements to detect and monitor environmental change. Consequently, data centers providing accessible, usable long-term data are essential in the earth sciences (see Box 1.3).
TABLE 1.4 Selected ESE Missions
Mission |
Objective |
Current Missions |
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Active Cavity Radiometer Irradiance Monitor III (ACRIM III) |
Measures total solar irradiance from the Sun. |
Earth Radiation Budget Satellite (ERBS) |
Investigates how energy from the Sun is absorbed and reemitted by the Earth, and determines the effects of human activities on the Earth’s radiation balance. |
Landsat 7 |
Provides multispectral, moderate-resolution digital images of the Earth’s continental and coastal areas, with global coverage on a seasonal basis. |
SeaSTAR |
Measures bio-optical properties of the global ocean. |
Terra |
Provides global data on the state of the atmosphere, land, and oceans, as well as their interactions with solar radiation and with one another. |
Total Ozone Mapping Spectrometer Earth Probe (TOMS-EP) |
Provides daily global measurements of the total column ozone. |
Tropical Rainfall Measurement Mission (TRMM) |
Monitors tropical rainfall and the associated release of energy that helps to power global atmospheric circulation. |
Quick Scatterometer (QuikSCAT) |
Records sea-surface wind speed and direction for global climate research, weather forecasting, and storm warning. |
Future Missions |
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Advanced Earth Observing Satellite (ADEOS)-II |
Measure near-surface wind velocity under all weather and cloud conditions over the Earth’s oceans. |
Aqua |
Measure clouds, precipitation, atmospheric temperature and moisture content, terrestrial snow, sea ice, and sea-surface temperature. |
Ice, Clouds, and Land Elevation Satellite (ICESat) |
Determine decadal variation of ice sheet thickness over Greenland and Antarctica, altitude and thickness of clouds, vegetation heights, land topography, and ocean surface and sea ice altimetry. |
Meteor |
Monitor the global distribution of aerosols, ozone, and other trace gases in the Earth’s atmosphere. |
Solar Radiation and Climate Experiment (SORCE) |
Provide total irradiance measurements (ultraviolet, extreme ultraviolet, and the visible to near infrared) required by climate studies. |
BOX 1.3 Applications of Earth Science Archives Archived data have proven to be extremely important for investigations of changes in the Earth’s atmosphere, oceans, and land cover. Examples include:
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THE CHANGING PARADIGM FOR NASA
With the adoption of the scientific goals of the Earth Science and Space Science Enterprises, NASA can no longer be viewed primarily as a technology-demonstration agency. Instead, NASA has defined itself as a knowledge-generating agency, with missions at the front end of the information pipeline. NASA data are a national resource; the stewardship and exploitation of NASA data are necessarily a national responsibility. The care of the data, including the tasks of archiving and distribution, must be accomplished so as to maximize knowledge enhancement, scientific impact, and discovery potential. The chapters following describe and evaluate the strategies adopted by NASA to date and make recommendations to enhance the usefulness and accessibility of the growing databases obtained from NASA missions.