EOS is the centerpiece of NASA’s Mission to Planet Earth, whose overall goal is to understand the total earth system (air, water, land, life, and their interactions) and the effects of natural and human-induced changes on the global environment. EOS has three major components: (1) a constellation of satellites designed to collect at least 15 years of key climate-related data; (2) a data and information system designed to operate the satellites and process, archive, and distribute the data; and (3) teams of scientists who develop algorithms for converting sensor data into useful information and conduct basic research using the information. The satellites, and data and information system, which will absorb most of the program’s funding, provide the researchers with measurements that will enable them to address established research priorities. EOS is designed to make 24 types of long-term measurements of solar irradiance and the earth’s atmosphere, land cover, ice sheets, and oceans from orbiting spacecraft. By 2002, when the full constellation will be in orbit, EOS will be generating data from 25 instruments on at least 10 spacecraft. Over the 20-year EOS data-collection phase, about 80 instruments will be launched on more than 30 satellites. As currently planned, the last EOS satellite will cease operations in 2020. EOS measurements will support researchers’ efforts to address Mission to Planet Earth’s research priorities: (1) determine the causes and consequences of changes in atmospheric ozone; (2) improve seasonal-to-interannual climate prediction; (3) determine the mechanisms of long-term climate variability; (4) document changes in land cover, biodiversity, and global productivity; and (5) understand earth processes that can lead to natural disasters and develop risk assessment capabilities for vulnerable regions. Mission to Planet Earth is NASA’s contribution to the governmentwide U.S. Global Change Research Program. An important goal of these interconnected efforts is to improve the predictive capability of numerical earth system models, especially global climate models that investigate and predict the general circulation of the atmosphere and ocean. NASA has identified a potentially large and diverse “user community” for EOS-related information. Members of this community could be, for example, educators, businessmen, and public policymakers. The focus of our analysis, however, is the EOS basic research community, by which we mean NASA’s currently funded EOS interdisciplinary science and instrument investigations. In our June 1995 report, we estimated that funding requirements of the EOS baseline program would total about $33 billion for fiscal years 1991 to 2022. This estimate was developed for the program described in NASA’s 1995 EOS reference handbook and included costs for satellites, launch services, data systems, science, construction of facilities, and civil service personnel. However, NASA later recognized that this program was not affordable in an environment of declining budgets and began studying ways to cut costs by using advanced technology and increasing collaboration with other agencies, international partners, and the commercial sector. NASA intended to use these future savings to fund more science under EOS and to reduce the program’s total cost. Over the past several years, the Congress has progressively reduced NASA’s planned spending on EOS for fiscal years 1990 to 2000 from $17 billion to $7.25 billion. In response, NASA changed EOS in 1991 and 1992 from a complete earth system measuring program that would have supported a wide array of global change investigations to a measurement program that will primarily support investigations of global changes to the earth’s climate. For example, NASA dropped the measurement of upper atmospheric chemistry and solid earth processes. Other changes followed in order to further adjust EOS to its progressively lower budget profile through 2000. NASA officials stated the current planned spending for EOS through 2000 is about $6.8 billion. The administration’s fiscal year 1997 request for Mission to Planet Earth is $1.402 billion, of which $846.8 million is for development of EOS’ data and information system, spacecraft, instruments, and algorithms. NASA’s request includes $47.5 million for EOS interdisciplinary science. According to NASA’s 5-year plan based on its fiscal year 1996 budget submission, NASA intends to increase spending on EOS interdisciplinary science to $73.2 million per year in fiscal year 2000. Like EOS-related space systems and information systems, the development of the EOS basic research community that will conduct interdisciplinary global climate change research requires planning. The current number of EOS investigations funded by NASA is relatively small, and NASA recognizes that it needs to increase their number, broaden the membership of EOS science teams, and take other steps to develop and sustain an EOS-era research community. NASA’s strategy for developing the EOS research community is partly based on increased funding. In 1995, it began efforts to fund additional investigations and to reevaluate the current investigations. NASA’s ability to add more investigations is uncertain within its expected future budgets, especially if it must depend on savings from improved technology and increased collaboration with others. The EOS program is currently funding 29 interdisciplinary science investigations that were selected in 1989 and 1990 to use data from EOS instruments in more than one earth science discipline, such as geology, oceanography, meteorology, and climatology. Scientists associated with these investigations serve as members of the Investigator Working Group, developing detailed science plans and assisting NASA in optimizing the scientific return of the EOS mission. Currently, these 29 investigations are led by 31 interdisciplinary principal investigators (2 of the interdisciplinary science investigations have coprincipal investigators). There are 354 coinvestigators associated with the 29 interdisciplinary science investigations, as well as 20 instrument principal investigators/team leaders and 197 other instrument team members. The number of EOS investigations is relatively small when compared with (1) the number of currently funded investigations associated with two pre-EOS missions—the Upper Atmosphere Research Satellite (UARS) and the U.S.-French Oceanography Satellite Ocean Topography Experiment (TOPEX/Poseidon)—to their EOS-era counterparts and (2) the ratio of the number of investigations to the raw data acquisition rate expected from instruments on EOS spacecraft to the number of investigations and raw data acquisition rates of UARS and TOPEX. The comparison is based on the following EOS spacecraft and instruments: AM; PM; Chemistry mission (CHEM); Landsat-7; Radar ALT; Laser ALT; Stratospheric Aerosol and Gas Experiment (SAGE) III on space station; and Solar Stellar Irradiance Comparison Experiment (SOLSTICE), Active Cavity Radiometer Irradiance Monitor (ACRIM), and Clouds and Earth’s Radiant Energy System (CERES) on flights of opportunity. The data rates of the EOS spacecraft and UARS/TOPEX are not strictly comparable because the instruments on the latter satellites do not directly observe the Earth. Imaging instruments are more data intensive than nonimaging instruments. However, data rate comparisons can serve as a rough indicator of the magnitude of potential research opportunities afforded by EOS and two pre-EOS-era missions. The National Aeronautics and Space Administration (NASA) used similar comparisons in its 1993 and 1995 editions of the EOS reference handbook. In the 1995 edition, NASA graphically compared the combined data rates of EOS-era satellites with the combined data rates of numerous pre-EOS-era (including UARS and TOPEX) and foreign satellites to demonstrate that the magnitude of potential research opportunities for EOS is much greater than for other combinations of Earth-sensing satellites. In its handbooks, NASA depicted the data streams flowing from the two groups of satellites to “10,000 users” in the 1993 edition and a more vaguely defined “user community” in the 1995 edition. In place of the broadly defined “users” and user community, we used the actual number of currently funded EOS, UARS, and TOPEX investigations to illustrate (1) that the magnitude of potential EOS basic research opportunities is much greater than those afforded by UARS and TOPEX (as indicated by their respective data rates) and (2) that the number of currently funded EOS investigations is small compared to the number of currently funded UARS and TOPEX investigations. UARS, launched in September 1991, consists of 10 instruments that are measuring the composition and temperature of the upper atmosphere, atmospheric winds, and energy from the sun. The UARS science investigations are led by 22 teams. NASA broadened the UARS science investigations in 1994 by selecting 40 additional teams led by “guest” investigators. It is also funding correlative measurement investigations led by 38 teams to develop an independent database to validate and complement measurements made by UARS’ instruments. In the EOS era, solar energy and atmospheric chemistry measurements will be made principally by the ACRIM, SAGE, and SOLSTICE instruments and the CHEM spacecraft. Currently, only 12 instrument and interdisciplinary science investigations are associated with these instruments and the CHEM spacecraft. In contrast, UARS supports research conducted by 62 instrument and science teams. TOPEX was launched in August 1992 to study the circulation of the world’s oceans. The primary instrument is an altimeter that measures the height of the satellite above the ocean, wind speed, and wave height. NASA and its French partner, Centre National d’Etudes Spatiales, selected 38 science investigations. The 38 TOPEX-related science teams have about 200 members, and NASA plans to solicit additional investigations. In the EOS era, the follow-on mission to TOPEX is Radar-ALT. An instrument team has not yet been selected, but only 7 of the 29 interdisciplinary science investigations currently plan to use Radar-ALT data. There is a large difference between the number of (1) currently funded EOS investigations and the expected volume of data from EOS and (2) the currently funded UARS and TOPEX investigations and volume of data of these two pre-EOS missions. The combined number of the UARS and TOPEX science investigations is a little larger than the current number of EOS investigations, even though EOS’ data rate (our indicator of the magnitude of potential research opportunities) is close to 1,000 times greater than the combined data rate of UARS and TOPEX. EOS will provide up to 42 million bits of data per second to 49 interdisciplinary science and instrument investigations. The corresponding ratio for UARS and TOPEX is a total of 48 thousand bits of data per second to 60 investigations. The National Research Council’s Board on Sustainable Development reviewed the U.S. Global Change Research Program, Mission to Planet Earth, and EOS in 1995 and stated that one of the “fundamental guiding principles” of the U.S. Global Change Research Program is an “open and accessible program” that will “encourage broad participation” by the government, academic, and private sectors. Some NASA officials and EOS investigators are concerned that the Earth sciences research community perceives EOS’ science teams as a “closed shop,” whereby membership on a current team is a precondition for conducting future EOS-related research. To counter this perception, NASA’s current strategy to expand the EOS research community involves (1) an open data access policy and (2) efforts to broaden and change the current community by adding investigations, reevaluating the current science investigations, and recruiting new investigators. A vital part of the EOS data policy is that EOS data will be available to everyone: there will be no period of exclusive access for funded investigators. This has not always been NASA’s policy. On some past Earth observing missions, funded investigators had exclusive use of the data for an extended period of time. For example, the original investigators associated with the Upper Atmosphere Research Satellite had exclusive access to the first year’s data for up to 2 years. EOS data users as a rule will not be charged more than the cost of distributing data to them. The data policy contemplates a variety of potential user groups, not all of whom will be engaged in basic research. In 1995, NASA sponsored a conference to better define the user groups. The conferees identified 12 potential user groups, of which only 3 were primarily composed of scientists. The others included commercial users, resource planners, and educational groups. NASA officials stated that about 10,000 Earth scientists might use EOS-related data. Even with the large size of this potential research community and the open-access data policy, the sufficiency of EOS investigations might appear to be the least of NASA’s problems. Even though 10,000 Earth scientists may be potential users of EOS data, they still need to be funded to conduct basic research. According to NASA officials, as a general rule, for this type of work, scientists analyze data when they are paid to do so. We sought to confirm this observation by reviewing the authorship of 172 journal articles about 2 pre-EOS-era satellites—UARS and TOPEX/Poseidon. Our review showed that publicly funded investigators wrote all but 10 of the articles. We reviewed the authorship of UARS and TOPEX articles published in scientific journals from the approximate dates of launch through May 1995; these articles were selected from a database consisting of about 4,500 periodicals. The principal investigators wrote 123 (72 percent) of the 172 articles. In addition, we identified two other kinds of investigators probably associated with the principal investigators and/or government funded—that is, investigators associated with the principal investigator’s institution (most often a university or government agency) or another government agency. These “associate” investigators wrote 39 (23 percent) of the journal articles. Not all people who get Earth sciences data use it to do basic research. For example, from January through May 1995, NASA’s Jet Propulsion Laboratory sent 55,521 TOPEX-related data files to 28,495 requesters through the Internet. This figure does not necessarily represent separate requesters. The laboratory does not know how these requesters use TOPEX data, but according to a laboratory official, data accessed through the Internet is generally not sufficient for doing basic research. Investigators want less processed data for this type of research. NASA originally solicited proposals for EOS interdisciplinary science and instrument investigations in January 1988. The solicitation noted that NASA planned to fund 10 to 20 science investigations, with other selections possible before the launch of the first EOS platform, then scheduled for late 1995. NASA received 458 proposals in response to its solicitation, including about 250 for interdisciplinary science investigations. As previously noted, 29 interdisciplinary science and 20 instrument investigations are being funded by NASA and its international partners. The lifetime of the science investigations was to extend for 4 years beyond the launch of the first satellite, or until 1999. In other words, NASA intended to add to this first group of investigations over a 10-year period (1989 to 1999). However, at a minimum, the lifetime of this first group of investigations has been extended to 13 years (1989 to 2002, including 4 years beyond AM-1’s 1998 launch date). NASA’s plan to supplement the first group of science investigations with a second group within 6 years was not too optimistic given its funding expectations at that time. NASA’s EOS mission planning (1982-87) took place during a time of expanding resources. During the 1980s, NASA’s funding increased each year, essentially doubling from about $5 billion to $10 billion between fiscal years 1981 and 1989. NASA has recognized that more EOS investigations are needed, and last year it took a first step to add more. NASA solicited proposals in September 1995 to address, among other things, specific interdisciplinary science issues that are not well covered by existing NASA-funded investigations. It received 134 interdisciplinary science proposals and hopes to add 20 to 25 investigations with grants of about $250,000 to $400,000 per year for a period of up to 3 years. NASA is funding the interdisciplinary science part of the September 1995 solicitation with a $9-million “funding wedge” created, in part, from reductions in the previously planned funding levels for some existing EOS investigations. According to a NASA official, no new money will be used to fund these investigators. It remains to be seen if NASA’s ability to generate future savings in the program will become a major factor in increasing the number of EOS investigations. Although potentially useful over the longer term, these grants will not immediately increase the number of EOS investigations in the near term because the announcement largely precludes investigators from analyzing data from the first EOS mission, AM-1, which is now scheduled for launch in 1998. Instead, NASA is asking for proposals on interdisciplinary research that primarily uses existing data sets from past satellite missions and field experiments.The nature and membership of the EOS science teams has largely remained unchanged for 6 years. According to NASA officials, this longevity has created a perception among some Earth scientists that currently funded investigators constitute a “closed shop.” NASA attempted to correct this perception by conducting an internal program review in 1992 and 1993 and an external peer review in 1995 and 1996. The review by EOS investigators’ peers in the Earth sciences research community is not yet finished, but it could lead to the possible deselection and recompetition of some EOS interdisciplinary science teams. NASA opted for the peer review, rather than have all the current investigations reevaluated as part of a new solicitation for proposals. NASA’s 1992-93 program review found weaknesses in many interdisciplinary science teams. The reviewers generally found that only 30 percent of 23 investigations could be rated “successful” in terms of science-related assessment measures. They also noted that “most teams need work in documenting their scientific progress, plans, and the policy relevance of their research to the Earth Science community, as well as to NASA.” The reviewers specifically noted that 67 percent (of 24 teams) had poor management plans, 61 percent (of 23 teams) had a less than satisfactory publication record, and 57 percent (of 23 teams) needed to improve their contacts with the EOS instrument teams. The review concluded that “for most teams, the biggest factor hindering their success is their lack of a good management plan—teams that do not have their own house in order will not benefit from increased collaborations” with other interdisciplinary and instrument teams. In October 1994, the Science Executive Committee of the EOS Investigator Working Group endorsed the need for a peer review and possible turnover of teams, if this would enhance the quality of EOS investigations. The Committee, however, rejected the idea that the existing investigations should be evaluated through a new competition. It noted that a new competition could cause a loss of credibility with EOS supporters and that many interdisciplinary science teams had committed themselves “far beyond” just their science tasks. In contrast, NASA struck a different balance between continuity and change in the pre-EOS-era U.S.-Japan Tropical Rainfall Measuring Mission. The goal of the spacecraft’s three principal instruments is to measure rainfall more accurately than before, particularly over the tropical oceans. The science of a long-term investigatory group was reevaluated after 3 years by holding a new funding competition for this program. NASA and Japan’s National Space Development Agency first solicited research proposals in 1990 for a possible launch in 1994. Both agencies selected a total of 35 investigators. The two space agencies in October 1993 again solicited research proposals for a launch now scheduled for 1997. The space agencies selected 27 of the original investigators and added 12 new investigators to the science team. The long-term growth of the EOS research community depends, in part, on NASA’s ability to recruit graduate students and newly graduated Earth scientists to use remotely sensed data. NASA supports prospective researchers in the Earth sciences through the graduate student Global Change Fellowship program. Successful candidates can be funded for up to 3 years, at $20,000 per year, primarily for tuition support and living expenses. NASA supported 112 fellowships for the 1993-94 academic year. In September 1995, NASA also established a new investigator program as part of Mission to Planet Earth and solicited proposals for 10 to 15 interdisciplinary investigations from recent Ph.D. recipients. The proposed investigations must be based on data from existing satellite missions. NASA received 65 proposals in response to this solicitation. while some of the multi-year reductions may be accomplished without serious effect on the program, it must be stated that the achievement of several essential elements (e.g., continuity of observations for 15 years) of the program are now at significantly greater risk. Despite this apprehension, most interdisciplinary science investigators have experienced or expect little or no effect of budgetary turbulence on their own research. In the 1992-93 program review, NASA’s investigators were generally optimistic that they could withstand EOS’ continuing budgetary turbulence. In 1995, investigators reaffirmed this optimism. As part of the 1992-93 program review, NASA asked EOS’ interdisciplinary science principal investigators to evaluate the effect changes to EOS would have on their work. The reviewers classified the 23 responding investigators’ remarks as follows: no effect (11 investigators, 48 percent); minor effect (8 investigators, 35 percent); and major effect (4 investigators, 17 percent). The program review followed the cancellation of three major EOS instruments over several years: Laser Atmospheric Wind Sounder (observation of lower atmospheric winds); High-Resolution Imaging Spectrometer (identification of surface composition); and Synthetic Aperture Radar (high-resolution global measurements of the Earth’s surface). Whether scientists planned to use a canceled instrument was a major part of how they perceived the impact on their work. Some investigators also cited changes to their ongoing research resulting from little or no growth in most of their fiscal year 1994 budgets. According to a NASA official, only seven investigations received as much as a 10-percent increase in their 1994 budget above the amount for fiscal year 1992. One investigator, citing a flat budget for 1994, said that as a result, coinvestigators could not give full attention to EOS-related research and that it was “difficult for us to contemplate an accelerated or broadened attack on the global change problems we are addressing.” Another investigator noted that such a budget meant that “some research tasks have to be trimmed” and would not “allow much flexibility in terms of new ideas and initiatives.” In 1995, NASA again asked the interdisciplinary science principal investigators to assess how changes over the previous 3 years to the EOS program had affected their future and ongoing research. The scientists cited the same mix of concerns as they had previously—namely, the loss of several instruments and lack of growth in their funding. One investigator noted that a 20-percent budget reduction in 1994 “decimated our attempts to carry out field studies in collaboration with team members.” His view, however, was unique. Most investigators reported that the changes had so far created only relatively minor problems that could be adequately resolved. A NASA official told us that a reason for investigators’ optimism is that NASA officials consciously tried to minimize the impact of budget reductions on EOS-related science. Starting in 1996, NASA plans to solicit additional Earth science research through a new Earth System Science Pathfinder program. This effort will be based on data sets collected by new satellite missions. According to NASA officials, the Pathfinder program is intended to develop quick turnaround, low-cost space missions for high priority Earth sciences research not being addressed by current programs, including EOS, thus providing an opportunity to accommodate new science priorities and to increase scientific participation in Mission to Planet Earth. The administration is requesting $20 million for Pathfinder in fiscal year 1997 and plans to request $30 million, $75 million, and $75 million for fiscal years 1998, 1999, and 2000, respectively—a total of $200 million over the next 4 fiscal years. After then, NASA plans to offset Pathfinder’s funding requirements with reductions generated from the introduction of lower cost technology into future Mission to Planet Earth-related research. Pathfinder’s goal is to launch one mission every year, starting in 1999. NASA estimates the life-cycle cost of each mission would not exceed $120 million and would include the cost of the launch vehicle, civil service labor, investigator support, and 2 years of spacecraft operations.However, NASA has not demonstrated that the potential value of Pathfinder’s science would exceed the potential value of additional EOS-related science, if savings allocated to Pathfinder were allocated to EOS science. NASA criticized our analysis and conclusions. NASA stated that our draft report underestimated the size of the EOS research community and the abilities of EOS investigators to process the large amount of data expected from EOS. We do not agree with NASA’ s description of our report’s focus and scope. Our objective was not to estimate the size of the EOS research or broader user communities, or to assess the abilities of current researchers to handle the large amount of data expected from EOS. Rather, our objective was to assess NASA’s plans for developing its basic research community, with specific focus on the number of currently funded EOS investigations. This issue is the basis for the majority of NASA’s concerns. To address NASA’s point, we revised our final report to clarify the specific focus and scope of our work. NASA said that our analysis of the number of EOS investigations did not consider the broader user community. Although NASA’s statement is correct, it was not the objective of our work to analyze the broader user community. We focused on comparing the number of NASA’s currently funded EOS-related investigations with the number of funded investigations associated with two pre-EOS-era missions. This comparison constituted our analytic framework and formed the basis of our conclusion that the magnitude of potential basic research opportunities afforded by EOS is much greater than those afforded by UARS and TOPEX, but the number of currently funded EOS investigations is relatively small compared to the number of investigations funded under the two pre-EOS-era missions. Our conclusion is consistent with NASA’s desire, as expressed in its comments on our draft report, “to expand the size of the direct EOS community,” and its actions during the course of our review to increase the number of EOS investigations in a budget-constrained environment. NASA’s comments also addressed our concern about its ability to increase the number of EOS investigations based on savings from EOS and other parts of Mission to Planet Earth. NASA stated that it has already made changes to lower EOS’ costs and that it will be able to decrease costs further while improving overall capability and maintaining data continuity. We have not evaluated NASA’s claims in this regard. In our draft report, we recommended that the NASA Administrator provide the Congress with an assessment of Pathfinder’s potential impact on NASA’s strategy for Earth system science research, including a determination that the potential value of Pathfinder’s investigations is expected to exceed the potential value of additional EOS investigations. NASA generally agreed with this recommendation, stating that it would provide a strategic assessment of Pathfinder. NASA also said it planned to proceed with the Pathfinder missions on the basis of already having analyzed the tradeoffs and having had its approach validated by outside review groups. The concern that prompted our recommendation in the draft report was the availability of adequate funding for EOS basic research given NASA’s funding strategy. That continues to be our concern and, in view of NASA’s position, we are changing our recommendation to the NASA Administrator to a matter for congressional consideration. Our purpose in making this change is to alert the Congress to the need to address the EOS funding issue before substantial funding commitments are made to the new Pathfinder program. NASA’s comments are in appendix V. In judging the extent to which it should support the proposed Earth System Science Pathfinder program, the Congress may wish to have NASA demonstrate that the potential value of Pathfinder investigations will exceed the potential value of additional EOS investigations that could be obtained with the same resources. To accomplish our objectives, we obtained documents related to EOS’ science program from and interviewed officials at NASA headquarters in Washington, D.C.; NASA’s Goddard Space Flight Center, Greenbelt, Maryland; and at the Jet Propulsion Laboratory, Pasadena, California. We attended the EOS Investigators Working Group meeting in June 1995 in Santa Fe, New Mexico, and the Payload Panel meeting in November 1995 in Annapolis, Maryland. In analyzing the development of the EOS research community, we reviewed information on pre-EOS Earth science ground- and space-based research, as well as EOS’ interdisciplinary science research. In analyzing the authorship of articles related to UARS and TOPEX/Poseidon, we used “Scisearch,” an international, multidisciplinary index to science literature. Scisearch indexes articles from approximately 4,500 scientific and technical journals. We used the scientists’ progress reports for 1992 to 1993, and 1995 to assess whether changes to EOS have adversely affected EOS’ interdisciplinary research. We performed our work between February 1995 and February 1996 in accordance with generally accepted government auditing standards. As agreed with your office, unless you publicly announce its contents earlier, we plan no further distribution of the report until 30 days from its issue date. At that time, we will send copies to other appropriate congressional committees; the NASA Administrator; and the Director, Office of Management and Budget. We will also make copies available to other interested parties upon request. Please contact me on (202) 512-8412 if you or your staff have any questions concerning this report. Major contributors to this report were Brad Hathaway, Frank Degnan, Thomas Mills, Richard Eiserman, and Richard Irving. The National Aeronautics and Space Administration (NASA) considers the following measurement sets to be critical to preserving the Earth system science approach of the Earth Observing System (EOS) and important to making environmental policy decisions. The information in appendixes I-IV was derived from NASA sources. The formation, dissipation, and radiative properties of clouds influence the atmosphere’s response to greenhouse forcing (i.e., mechanisms that promote the greenhouse effect). The net effect of cloud forcing and feedback determines the energy budget of Earth and its cozy temperature, which supports life. Earth’s radiation budget drives the biological and physical processes of the atmosphere, land, and ocean, which in turn affect water resources, agriculture, and food production. There is a net outflow of atmospheric moisture from the tropics to the higher latitudes. This redistribution is accomplished through evaporation and precipitation, which determine the freshwater resources for agricultural and industrial development. Tropospheric chemistry is linked to the circulation of Earth’s water (the “hydrologic cycle”), the ecosystem, and transformations of greenhouse gases in the atmosphere, thus determining the oxidizing capacity of the atmosphere for cleansing pollutants. Stratospheric chemistry measurements involve chemical reactions, interactions between the sun and the atmosphere, and the sources and sinks of gases, such as ozone, that are critical to Earth’s radiation balance. An aerosol is a fine solid or liquid particle suspended in gas, such as the atmosphere. Aerosols affect the climate through their radiative properties by serving as nuclei for the condensation of clouds. Aerosols tend to cool Earth’s atmosphere, thus offsetting some of the warming effects of greenhouse gases. Along with atmospheric humidity, atmospheric temperature is used in short-term weather prediction and long-term climate monitoring. Improved measurement accuracy, precision, and spatial and temporal coverage will enhance weather prediction skills beyond current limits and reduce weather prediction “busts,” or failures. See “Atmospheric Temperature.” Lightning measurements will include the distribution and variability of both cloud-to-cloud and cloud-to-ground lightning. Electrical discharge contributes to the formation and dissipation of certain trace gases in the atmosphere. Sustained changes in the total radiation output from the sun could contribute to significant climate changes on Earth over time. Solar radiation is the main source of energy for biological activities on Earth. Out of the entire spectrum of radiation that Earth receives from the sun, the ultraviolet portion is the dominant energy source for the Earth’s atmosphere. Small changes in the radiation field have an important effect on atmospheric temperature, chemistry, structure, and dynamics. Excess ultraviolet energy on the Earth’s surface is harmful to living organisms. Land use includes monitoring crops for efficient irrigation and pest control, public lands for good stewardship, and urban areas for development. Some changes in land use, such as deforestation and biomass burning, reduce the standing stock of vegetation, release carbon dioxide into the atmosphere, and reduce the capacity for the removal of carbon dioxide from the atmosphere. Terrestrial vegetation absorbs atmospheric carbon dioxide by photosynthesis to offset its greenhouse warming effect. Terrestrial surface temperature controls the formation and distribution of atmospheric water vapor and also contributes to the determination of cloud amount. In addition, surface temperatures control the biological activity and health of agricultural fields, forests, and other natural ecosystems. Biomass burning releases carbon dioxide into the atmosphere and also increases concentrations of other harmful gases, such as carbon monoxide and nitrogen oxides. Land cover monitoring can be used to assess potential fire hazards and monitor fire recovery in natural ecosystems. The volcanic ejection of aerosols and particulates into the atmosphere can increase precipitation and ozone destruction and cause the lowering of global temperatures. Volcanic activities also contribute to the formation of continents. Surface wetness controls the availability of fresh water resources for agricultural and industrial activities. Sea surface temperature measurements are important to understanding heat exchange between the ocean and the atmosphere. Such an understanding will contribute to the development of accurate general circulation models, which enhance our understanding of seasonal and interannual climate variations that contribute to hurricanes, floods, and other natural hazards. Planktonic marine organisms and dissolved organic matter play a major role in the carbon cycle, as they incorporate, or “fix,” about as much carbon as land plants. This contributes to removing carbon dioxide from the atmosphere and to offsetting the greenhouse effect. Surface winds over the oceans contribute to ocean circulation and the interaction between the air and sea, which affect short-term and long-term climate variations. Sea height and ocean circulation are related. Ocean circulation transports water, heat, salt, and chemicals around the planet. Accurate information about these circulation patterns should contribute to understanding the oceans’ impact on weather, climate, and marine life, and thus the fisheries industry and other maritime commerce. Measurements of the polar ice caps, including ice sheet elevation and ice volume, will determine the contribution of the ice sheets to sea-level variation. These data will also contribute to understanding the role of the polar ice caps in Earth’s freshwater and energy budgets, as well as climate fluctuations. Measurements of the extent and thickness of sea ice will help determine atmospheric warming. Sea ice measurements will also be useful to operational ice forecasting centers, thus affecting maritime commerce. Snow cover, extent, and duration determine fresh water resources, especially in Alpine regions of the world. Active Cavity Radiometer Irradiance Monitor (ACRIM) monitors the variability of total solar irradiance. Atmospheric Infrared Sounder (AIRS) measures atmospheric temperature and humidity. AMSR (Japan) Advanced Microwave Scanning Radiometer (AMSR) observes atmospheric and oceanic water vapor profiles and determines precipitation, water vapor distribution, cloud water, sea surface temperature, sea ice, and sea surface wind speed. Advanced Microwave Sounding Unit (AMSU) measures atmospheric temperature. ASTER (Japan) Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) provides high spatial resolution images of the land surface, water, ice, and clouds. Clouds and the Earth’s Radiant Energy System (CERES) measures Earth’s radiation budget and atmospheric radiation. DFA (France) Dual Frequency Altimeter (DFA) maps the topography of the sea surface and its impact on ocean circulation. Earth Observing Scanning Polarimeter (EOSP) globally maps radiance and linear polarization of reflected and scattered sunlight to measure atmospheric aerosols. Enhanced Thematic Mapper Plus (ETM+) provides high spatial resolution images of the land surface, water, ice, and clouds. Geoscience Laser Altimeter System (GLAS) measures ice sheet topography, cloud heights, and aerosol vertical structure. HIRDLS (UK-US) High-Resolution Dynamics Limb Sounder (HIRDLS) observes gases and aerosols in the troposphere, stratosphere, and mesosphere to assess their role in the global climate system. Landsat Advanced Technology Instrument (LATI) provides high spatial resolution images of the land surface, water, ice, and clouds beyond Landsat ETM+. Lightning Imaging Sensor (LIS) measures the distribution and variability of lightning. Microwave Humidity Sounder (MHS) provides atmospheric water vapor profiles. Multi-Angle Imaging Spectroradiometer (MISR) measures the top-of-the-atmosphere, cloud, and surface angular reflectance. Microwave Limb Sounder (MLS) measures chemistry from the upper troposphere to the lower thermosphere. (continued) Moderate-Resolution Imaging Spectroradiometer (MODIS) studies biological and physical processes in the atmosphere, the oceans, and on land. MOPITT (Canada) Measurements of Pollution in the Troposphere (MOPITT) measures upwelling radiance to produce tropospheric carbon monoxide profiles and total column methane. Microwave Radiometer (MR) provides atmospheric water vapor measurements for DFA. ODUS (Japan) Ozone Dynamics Ultraviolet Spectrometer (ODUS) measures total column ozone. Stratospheric Aerosol and Gas Experiment III (SAGE III) provides profiles of aerosols, ozone, and trace gases in the mesosphere, stratosphere, and troposphere. Provides all-weather measurements of ocean surface wind speed and direction. Solar Stellar Irradiance Comparison Experiment (SOLSTICE) measures full-disk solar ultraviolet irradiance. Tropospheric Emission Spectrometer (TES) provides profiles of all infrared active species from Earth’s surface to the lower stratosphere. Mission continues Landsat land-imaging satellite series. Future Landsat-type instrument is planned for AM-2 and AM-3. Morning equator-crossing mission (AM series) will study clouds, aerosols, and radiation balance; the terrestrial ecosystem; land use; soils; terrestrial energy/moisture; tropospheric chemical composition; volcanoes; and ocean productivity. ASTER and MOPITT will be on AM-1 only. EOSP and LATI will be on AM-2 and AM-3 only. Afternoon equator-crossing mission (PM series) will study cloud formation, precipitation, and radiative properties; air-sea fluxes of energy and moisture; sea-ice extent; and ocean primary productivity. The PM series will carry prototypes of future operational weather satellite instruments. Chemistry mission (CHEM series) will study atmospheric chemical composition; chemistry-climate interactions; and air-sea exchange of chemicals and energy. ODUS will be on CHEM-1 only. A later CHEM flight may include SAGE III. Laser altimeter mission (LaserALT series) will study ice sheet mass balance. Radar altimeter mission (RadarALT series) will study ocean circulation. RadarALT is a joint mission with France. SAGE III instrument carried on International Space Station (ISS) and Russian Meteor satellite will study distribution of aerosols, ozone profiles, and greenhouse gases in the lower stratosphere. Tropical Rainfall Measuring Mission (TRMM) will study precipitation and Earth radiation budget in the tropics and high latitudes. TRMM is a joint mission with Japan. Japanese Advanced Earth Observing System II (ADEOS II) satellite carrying NASA scatterometer instrument will study ocean surface wind vectors. Mission will monitor the variability of total solar irradiance and is currently planned to fly on a series of small satellites. Mission will study Earth’s radiation budget and atmospheric radiation. Mission will study full-disk solar ultraviolet irradiance. 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Timeline bars denote periods during which at least one copy of the indicated instrument is in orbit. EOS science objectives are listed below, along with the interdisciplinary investigations designed to address them. These investigations are intended to cross discipline boundaries, and therefore, address more than one science objective. The Water and Energy Cycles objective covers the formation, dissipation, and radiative properties of clouds, which influence the atmosphere’s response to greenhouse forcing. In addition, Water and Energy Cycles include large-scale hydrology and moisture processes, such as precipitation and evaporation. National Center for Atmospheric Research Project to Interface Modeling on Global and Regional Scales With EOS Observations. This investigation is intended to use surface and atmospheric data sources to improve climate models and their predictions of global change. Components of climate models to be addressed include surface-atmosphere interactions, the hydrologic cycle, global energy balance, cloud and aerosol radiative fields, and atmospheric chemical cycles. Climate Processes Over the Oceans. Climate is strongly influenced by the amount and distribution of water vapor, liquid water, and ice suspended in the atmosphere. This atmospheric water, and the climate over land areas, is largely controlled by processes occurring over the oceans. This investigation will improve modeling of both the atmosphere and its interactions with the ocean. It will address the roles of circulation, clouds, radiation, water vapor, and precipitation in climate change as well as the role of ocean-atmosphere interactions in the energy and water cycles. Hydrologic Processes and Climate Interdisciplinary Investigation. The global water and energy cycles link the atmosphere, land, and ocean. In addition, water supports life and plays a crucial role in climate regulation. This investigation is to enhance our understanding of the physical processes that affect these cycles. The Processing, Evaluation, and Impact on Numerical Weather Prediction of AIRS, AMSU, and MODIS Data in the Tropics and Southern Hemisphere. This investigation involves the development of algorithms and techniques to improve atmospheric science, specifically numerical weather prediction models, using three EOS instruments. Investigation of the Atmosphere-Ocean-Land System Related to Climate Processes. The atmosphere, ocean, and land interact with each other through the exchanges of heat energy, momentum, and water substance. These interactions influence climate. This investigation will examine the atmosphere-ocean-land system by pursuing seven supporting studies that will involve both observations and modeling. The Development and Use of a Four-Dimensional Atmospheric-Ocean-Land Data Assimilation System for EOS. This investigation will incorporate all available data, from a variety of sources, into a single model of the Earth system. This model can then be used to project the Earth system beyond the range of actual observations, estimate expected values of observations to assess instrument quality, provide products for environmental studies, and supplement observations by estimating quantities that are difficult or impossible to observe. An Interdisciplinary Investigation of Clouds and the Earth’s Radiant Energy System: Analysis. This investigation will examine the role of clouds and radiative energy balance in the climate system. Studies include cloud feedback mechanisms that can greatly modify the response of the climate system to increased greenhouse gases. The Oceans objective covers the exchange of energy, water, and chemicals between the ocean and atmosphere, and between the upper layers of the ocean and the deep ocean. Coupled Atmosphere-Ocean Processes and Primary Production in the Southern Oceans. The southern ocean plays an important role in both the carbon cycle and heat exchange between the ocean and atmosphere. This investigation will focus on developing predictive models so we can better understand the effects of changes in the physical forcing of the ocean (e.g., small shifts in the location of westerly wind systems may affect ocean processes). Biogeochemical Fluxes at the Ocean/Atmosphere Interface. Solar radiation impinging on the oceans creates chemical, physical, and biological effects. One result is the creation of gases, such as carbon dioxide, dimethyl-sulfide, and carbon monoxide, which are then circulated by wind and water. This investigation will develop models to better understand these gases and the influence of oceanic processes upon them. Interdisciplinary Studies of the Relationships Between Climate, Ocean Circulation, Biological Processes, and Renewable Marine Resources. This investigation will study (1) the ocean’s role in climate change, particularly in the Australian region; (2) the influence of the carbon cycle in Australia’s waters on the global carbon cycle; and (3) changes in Australian oceanography and the implications for marine ecosystems, including commercial fisheries. The Role of Air-Sea Exchanges and Ocean Circulation in Climate Variability. Exchanges of water, momentum, and heat at the interface of the ocean and atmosphere drive the transport and change the storage of heat, water, and greenhouse gases, thus moderating the world’s climate. This investigation will study these exchanges and ocean circulation in order to improve our understanding of natural global changes and enable us to discern human-induced effects. Polar Exchange at the Sea Surface: the Interaction of Ocean, Ice, and Atmosphere. This is an investigation of energy exchanges in Earth’s polar regions, both at the atmosphere-ice-ocean interface and lower latitudes. It will study the role these processes play in global oceanic and atmospheric circulation and help improve our understanding of whether polar regions show any sign of climate change. Middle and High Latitude Oceanic Variability Study. This investigation will examine the variability of the atmosphere’s influence on the oceans, the effect on the oceanic response, and the resulting effect on biological productivity in the oceans. The study will focus on the mid- to high-latitude regions of the oceans. It will examine changes in the surface fluxes of momentum, heat, water, and radiation, as well as the variability of ocean circulation and biological activity. Earth System Dynamics: the Determination and Interpretation of the Global Angular Momentum Budget Using EOS. Momentum and mass transport among the atmosphere, oceans, and solid Earth produce changes in the planet’s rotation and gravity field. Predictions of these changes based on the mass and motion of air and water can be compared with observations to improve models of the interactions of the oceans, atmosphere, and solid Earth. This investigation will examine these interactions as represented by the exchange of angular momentum, mass, and energy among these components. The Chemistry of the Troposphere and Lower Stratosphere objective includes links to the hydrologic cycle and ecosystems, transformations of greenhouse gases in the atmosphere, and interactions inducing climate change. Interannual Variability of the Global Carbon, Energy, and Hydrologic Cycles. Analysis of the carbon, energy, and water cycles may increase the predictability of climate change. The goals of this investigation are to (1) understand contemporary climate variability and trends and (2) contribute to our ability to predict the impact of human activities on the climate. Changes in Biogeochemical Cycles. Models of biogeochemical cycles can be used to project the interactions of atmospheric composition, climate, terrestrial and aquatic ecosystems, ocean circulation and sea level, and human-induced effects. This investigation will develop models and databases to describe the dynamics of water, carbon, nitrogen, and trace gases over seasonal-to-century time scales. The Land Surface Hydrology and Ecosystem Processes objective covers sources and sinks of greenhouse gases, the exchange of moisture and energy between the land surface and atmosphere, and changes in land cover. Investigations in this category could result in improved estimates of runoff over the land surface and into the oceans. Global Water Cycle: Extension Across the Earth Sciences. The global water cycle stimulates, regulates, and responds to the other components of the Earth system on regional and global scales. This investigation is aimed at developing a hierarchy of models, using EOS data, that will contribute to our understanding of cloud cover and radiative transfer, as well as energy and moisture changes at the interface of the atmosphere with the oceans, cryosphere, and land surface. These models will contribute to the prediction of changes in water balance and climate. Long-Term Monitoring of the Amazon Ecosystems Through EOS: From Patterns to Processes. Natural and human-induced changes in the Amazon are expected to disrupt regional vegetation distributions, alter the physical and chemical characteristics of the continental river system, and change regional hydroclimatology, possibly influencing global climate patterns. The aim of this investigation is to understand the circulation of water, sediment, and nutrients through the basin. Northern Biosphere Observation and Modeling Experiment. Natural and human-induced climate changes in the northern latitudes will affect terrestrial ecosystems, and feedbacks from these changing systems will influence the climate. The goal of this study is to better understand the relationship between the climate and northern ecosystems over a range of spatial scales. Hydrology, Hydrochemical Modeling, and Remote Sensing in Seasonally Snow-Covered Alpine Drainage Basins. Seasonally snow-covered Alpine regions are important to the hydrologic cycle, as they are a major source of water for runoff, ground water recharge, and agriculture. This investigation will monitor conditions in Alpine basins and develop models to better understand the cycling of water, chemicals, and nutrients in these areas. Climate, Erosion, and Tectonics in Mountain Systems. In mountain belts, climatic and tectonic processes produce Earth’s highest rates of weathering and erosion. Alpine regions are important to downstream hydrology, providing both inorganic and organic material to lowland areas. This investigation will observe the effects of climate changes on Alpine land processes and develop models to improve our understanding of these interactions. The Hydrologic Cycle and Climatic Processes in Arid and Semiarid Lands. Knowledge of the hydrologic cycle will help scientists predict the effects of natural and human-induced climate change. This investigation will study the hydrologic cycle and climatic processes in arid and semiarid lands, where agricultural productivity is especially sensitive to changes in the cycle. Using Multi-Sensor Data to Model Factors Limiting Carbon Balance in Global Arid and Semiarid Land. This investigation will address the role of arid and semiarid lands in processes affecting the global environment, such as the production and consumption of trace gases. It will also examine the vulnerability of these lands to climate change in terms of productivity and soil quality, and develop predictive models of ecosystem function for dry lands. Biosphere-Atmosphere Interactions. This investigation is to improve our understanding of the role of the terrestrial biosphere in global change. It will cover short-term interactions between the land and atmosphere, such as biophysics, as well as long-term interactions, such as ecology and human-induced impacts. The goal of the investigation is to understand and predict the response of the biosphere-atmosphere system to global change, specifically to the increase in atmospheric carbon dioxide. Glaciers and Polar Ice Sheet measurements could contribute to predictions of sea level and global water balance. Use of the Cryospheric System to Monitor Global Change in Canada. The cryosphere is an important component of the global climate system, and better understanding of cryospheric processes may improve global climate models. This investigation seeks to understand cryospheric variations, develop models that will improve our knowledge of the role of the cryosphere in the climate system, and use various cryospheric data sets to support climate monitoring and model development. The Chemistry of the Middle and Upper Stratosphere objective includes chemical reactions, solar-atmosphere relations, and sources and sinks of radiatively important gases. Observational and Modeling Studies of Radiative, Chemical, and Dynamical Interactions on the Earth’s Atmosphere. Understanding the circulation, transformations, and sources and sinks of gases, such as carbon dioxide, water vapor, ozone, and chlorofluorocarbons, is important in dealing with the issues of global warming, ozone depletion, and the coupling of atmospheric chemistry and climate. This investigation seeks to improve our understanding of the fundamental processes influencing these gases in the atmosphere and contribute to the development of a predictive capability for global change studies. Chemical, Dynamical, and Radiative Interactions Through the Middle Atmosphere and Thermosphere. Carbon dioxide and ozone play important radiative roles in the middle atmosphere. Ozone absorbs ultraviolet radiation, heating the middle atmosphere and shielding the biosphere from dangerous ultraviolet dosages. The interactions of other gases, as well as temperature and middle atmosphere circulation, affect ozone. This investigation will improve our understanding of interactions in the middle atmosphere and our ability to predict long-term atmospheric trends. Investigation of the Chemical and Dynamical Changes in the Stratosphere. Chemical changes in the atmosphere are occurring largely as a result of changes in the surface emission of trace gases. This investigation will focus on the response of ozone to trace gas changes, isolating natural from human-induced changes to determine their effects on ozone and to assess radiative and dynamical feedbacks. The Solid Earth objective deals with volcanoes and their role in climate change. A Global Assessment of Active Volcanism, Volcanic Hazards, and Volcanic Inputs to the Atmosphere from EOS. The injection of material from volcanoes into the atmosphere can affect the local or hemispheric climate. This investigation will improve our understanding of the processes behind volcanic eruptions; study the injection of sulfur dioxide, water vapor, carbon dioxide, and other gases into the atmosphere; and place eruptions into the context of the regional tectonic setting of the volcano. The following are GAO’s comments on NASA’s letter dated May 17, 1996. Investigations to begin in 1996 cannot depend solely on data from EOS instruments because the earliest launch dates are planned for 1997 (for ) and 1998 (for EOS-AM-1). Instead, research plans should be based on use of existing data sets . . . or expected data from relevant near-term (1996-1997) satellite missions and field experiments. 8. Our draft report discussed the 1995-96 peer review, noting that the review could lead to possible deselection and recompetition of some EOS science teams. 9. We incorporated the amount of funds involved in the program into the report’s text. 10. We included NASA’s current estimate of planned EOS spending through fiscal year 2000 in the report’s text. 11. We revised our report to include NASA’s comments about lower program baseline costs and its confidence that it will decrease costs further. 12. We deleted the material NASA is referring to. The first copy of each GAO report and testimony is free. Additional copies are $2 each. Orders should be sent to the following address, accompanied by a check or money order made out to the Superintendent of Documents, when necessary. VISA and MasterCard credit cards are accepted, also. Orders for 100 or more copies to be mailed to a single address are discounted 25 percent. U.S. General Accounting Office P.O. Box 6015 Gaithersburg, MD 20884-6015 Room 1100 700 4th St. NW (corner of 4th and G Sts. NW) U.S. General Accounting Office Washington, DC Orders may also be placed by calling (202) 512-6000 or by using fax number (301) 258-4066, or TDD (301) 413-0006. 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Summary: Pursuant to a congressional request, GAO reviewed the National Aeronautics and Space Administration's (NASA) plans for funding its Earth Observing System (EOS) and developing EOS-related basic research, focusing on: (1) the current number of EOS science investigations; (2) researchers' views on whether changes to EOS have adversely affected their ability to carry out their interdisciplinary earth sciences investigations; and (3) the Earth System Science Pathfinder program and its potential impact on future EOS investigations. GAO found that: (1) NASA funds 29 interdisciplinary science investigations that use data from EOS instruments in more than one earth science discipline; (2) to expand the EOS research community, NASA plans to maintain an open data access policy, add investigations, reevaluate current science investigations, and recruit new investigators; (3) most EOS interdisciplinary scientists believe that EOS budgetary reductions have little or no effect on their work; and (4) NASA plans to use anticipated savings resulting from improved technology to fund more investigations and request a total of $200 million over the next 4 fiscal years for its Earth System Science Pathfinder program.