Natural and human-induced changes in the Earth system—from our planet’s interior to the land surface, ocean, and atmosphere—affect all aspects of life and society. To understand and respond to these changes and develop tools for decision making, Earth system models assimilate foundational observations collected from the land, sea, air, and space (NRC, 2008). NASA, the Department of Commerce (National Oceanic and Atmospheric Administration [NOAA]), and the Department of the Interior (U.S. Geological Survey) are the civil federal agencies with programs that use the vantage point of space to enable these observations, with NASA having a lead role in observations that aim to advance the study of Earth as an integrated dynamic system of chemical, biological, and physical processes—“Earth system science.”
NASA’s stated purpose of its Earth science program is “the development of a scientific understanding of Earth’s system and its response to natural or human-induced changes and to improve prediction of climate, weather, and natural hazards” (NASA, 2014). Within NASA, the Earth Science Division (ESD) is responsible for coordinating satellite and suborbital missions for long-term global observations of the land surface, biosphere, solid Earth, atmosphere, and oceans (NASA, 2014).
ESD develops its observing strategy in consultation with the scientific community and in response to congressional and executive branch direction. A notable expression of the scientific community’s overarching objectives for NASA Earth science is found in the 2007 National Research Council (NRC) decadal survey Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond (NRC, 2007). By design, the decadal survey involved a broad swath of Earth scientists and end users of information1 derived from Earth observations. The survey recommendations were thus an expression of a “bottom-up” consensus of research priorities that span disciplinary boundaries; these recommendations are given particular weight within NASA.2 ESD also responds to direction to NASA from Congress (for example, the restoration in 2009—3 years before scheduled
1 The decadal survey attempted to prioritize elements of its observing strategy with relevance to society as the foremost consideration. The survey committee—the authors of the survey report—recommended a national strategy for Earth observations from space whose overarching objective would be “a program of scientific discovery and development of applications that will enhance economic competitiveness, protect life and property, and assist in the stewardship of the planet for this and future generations” (NRC, 2007, p. 2).
2 See NASA, “Decadal Survey,” http://science.nasa.gov/earth-science/decadal-surveys/, accessed August 5, 2014. The 2007 Earth science and applications from space decadal survey (NRC, 2007) will be repeated on an approximately 10-year cycle per Public Law 110-442, the NASA Authorization Act of 2008. Thus, work on the next decadal survey is expected to begin in 2015 and be completed in 2017.
launch—of the thermal infrared instrument to the Landsat Data Continuity Mission) and the Administration (e.g., the 2010 “climate-centric” architecture; NASA, 2010).
ESD denotes “foundational” missions as missions in development at the time the 2007 NRC decadal survey was published. They include Aquarius, Suomi National Polar-orbiting Partnership (S-NPP), Landsat Data Continuity Mission (LDCM), and the Global Precipitation Measurement (GPM), all of which have been implemented successfully.3,4 In addition to the foundational missions, ESD is developing new missions based on the recommendations in the 2007 decadal survey (NRC, 2007) and climate continuity missions, which respond to both the recommendations of the decadal survey and the climate-centric architecture (NASA, 2010). These include Soil Moisture Active-Passive (SMAP),5 which was launched successfully in January 2015; Climate Absolute Radiance and Refractivity Observatory (CLARREO);6 Ice, Cloud and land Elevation Satellite (ICESat-II);7 Deformation, Ecosystem Structure, and Dynamics of Ice (DESDynI);8 Hyperspectral Infrared Imager (HyspIRI);9 Active Sensing of CO2 Emissions Over Nights, Days, and Seasons (ASCENDS);10 Surface Water and Ocean Topography (SWOT);11 Geostationary Coastal and Air Pollution Events (GEO-CAPE);12 and Aerosol-Clouds-Ecosystems (ACE).13,14 Earth Venture, also a recommendation of the decadal survey, is now an element of NASA’s Earth System Science Pathfinder Program.15 It consists of low-cost, competed suborbital and orbital missions as well as instruments for Missions of Opportunity. The Climate Continuity missions include: Orbiting Carbon Observatory-2 (OCO-2),16 Stratospheric Aerosol and Gas Experiment-III (SAGE III),17 Gravity Recovery and Climate Experiment Follow-on (GRACE-FO),18 and Pre-Aerosol, Clouds, and Ocean Ecosystem (PACE).19
Starting in fiscal year 2014, the Administration directed NASA to assume responsibility for a suite of climate-relevant observations for the purpose of continuing a multi-decadal data record in ozone profiling, Earth radiation budget, and total solar irradiance. These measurements were to have been implemented by NOAA with the Radiation Budget Instrument (RBI) and the Ozone Mapping and Profiler Suite Limb profiler (OMPS-L) on NOAA’s Joint Polar Satellite System 2 (JPSS-2) series, and the Total Solar Irradiance Instrument 2 (TSIS-2) instrument flown separately. NASA received a one-time funding increment of $40 million in 2014 for these instruments; however, this is only a fraction of the estimated $200-$300 million cost for their implementation.20 Further, the Senate Appro-
4 The committee learned after report writing that the Aquarius mission ended in June 2015 following a hardware component failure that resulted in the loss of onboard power regulation and spacecraft attitude stabilization.
5 NASA, “Soil Moisture Active-Passive (SMAP),” http://science.nasa.gov/missions/smap/. The committee learned after report writing that the L-band radar on SMAP ceased transmission in July 2015. SMAP’s L-band radiometer continues to operate normally, and NASA expects most of the mission’s science objectives will be met. See “NASA Soil Moisture Radar Ends Operations, Mission Science Continues,” September 2, 2015, http://smap.jpl.nasa.gov/news/1247/.
6 NASA is studying options for lower cost implementation of CLARREO while still achieving a majority of its science objectives; see NASA Langley Research Center (LaRC), “About CLARREO: Mission Concept,” http://clarreo.larc.nasa.gov/about-mission.html.
14 Budget cuts in 2012 forced a revaluation of the DESDynI mission. NASA is now implementing the L-band synthetic aperture radar component of DESDynI as part of NISAR (http://nisar.jpl.nasa.gov/), the NASA-ISRO (Indian Space Research Organisation) SAR Mission.
15 NASA, “Earth System Science Pathfinder Program,” http://science.nasa.gov/about-us/smd-programs/earth-system-science-pathfinder/.
18 NASA JPL, “Gravity Recovery and Climate Experiment Follow-on (GRACE-FO),” http://www.jpl.nasa.gov/missions/gravity-recoveryand-climate-experiment-follow-on-grace-fo/.
20 Thus, as ESD Director Michael Freilich explained in comments on October 29, 2013, to the NRC Committee on Earth Science and Applications from Space, which was meeting in Washington, D.C., NASA is examining alternative methods that could allow for lower-cost implementation. Also see Leone (2013).
priations Committee initiated a budget bill (not passed) that directed the development costs and responsibilities for the Deep Space Climate Observatory (DSCOVR) and Jason-3 to be transferred from NOAA to NASA ESD.21
As shown in Figure 1.1 and Table 1.1, the Earth Science program’s increasing responsibility for sustained continuity measurements occurs against the backdrop of enacted budgets that have been roughly level in recent years. Pressures on the budget also come from a backlog of decadal survey-recommended missions (NRC, 2012) and an increasing demand for Earth observations to support societal applications (NSTC, 2014).
Space-borne measurements carried out by NASA ESD are typically categorized as research while the operational space-borne measurements carried out by NOAA’s National Environmental Satellite, Data, and Information Service (NESDIS) are frequently referred to as monitoring. This delineation is an artificial characterization because both sets of measurements have and continue to play critical roles in advancing Earth system science. Nowhere is this more evident than in understanding global climate change, where the time scales of “research” are those traditionally ascribed to “monitoring.” Depending on the spatial and temporal scales of interest and the nature of the particular process, the climate change “signal” to be detected may be small relative to other sources of variability. For example, attribution of a change in sea surface temperatures due to greenhouse gases requires measurements that average over periods long enough to distinguish the warming signal from the larger seasonal and decadal variability of naturally occurring phenomena, such as the El Niño and La Niña.22
Detection and attribution of climatic changes and long-term trends in the Earth system—addressing, for example, land cover and land use, storm intensity, ground water change, aerosols, ozone pollution and recovery, ice mass loss, and sea level change—require sustained measurements. Such measurements are also necessary to understand climate processes characterized by low-frequency variability. Because changes on a wide range of time and space scales affect Earth, each measurement’s sampling characteristics need to be carefully designed to meet well-defined scientific and societal sampling objectives. Program plans for sustained measurements are based on current knowledge of the Earth system; however, they also must accommodate expanded understanding or unanticipated developments regarding climate and other global change. An observing system may very well reveal unexpected phenomena such as the Antarctic ozone hole, the depletion of subsurface aquifers, or the frequency/occurrence of natural, low-frequency events like El Niño and La Niña. Scientific opportunities are lost and the scientific basis for decision making eroded if the observing strategy cannot adapt accordingly. In addition to their scientific value, long-term observations (e.g., atmospheric carbon dioxide concentrations, sea level change, solar output) have become the focus of policy debates on anthropogenic contributions to global warming (Myhre et al., 2013). The especially stringent requirements for a climate-quality record of the Sun’s total irradiance at Earth are discussed in a 2013 NRC report (NRC, 2013).
The ad hoc committee formed in response to the NASA study request (“Statement of Task,” Appendix A) was asked to develop a framework to assist NASA’s ESD in their determinations of when a measurement(s) or data set(s) should be collected for durations longer than the typical lifetimes of single satellite missions. In particular, and considering the expected constrained budgets for the NASA Earth science program, the committee was asked to:
- Provide working definitions of, and describe the roles for “continuity” for the measurements and data sets ESD initiates and uses to accomplish Earth system science objectives; and
21 The President’s fiscal year 2016 budget, which was released on February 2, 2015, after a draft of this report had been submitted for external peer review, proposes to transfer responsibility for ocean altimetry missions following Jason-3 from NOAA to NASA. See page ES-37 in NASA, “FY 2016 President’s Budget Request Summary,” http://www.nasa.gov/sites/default/files/files/NASA_FY_2016_Budget_Estimates.pdf.
22 On attribution, see Bindoff et al. (2013). On the need for a blend of short-term, focused measurements as well as systematic, long-term measurements, see NRC (2000).
FIGURE 1.1 Earth science budget: fiscal year (FY) 2016 request/appropriation. SOURCE: Michael H. Freilich, NASA Headquarters, “NASA Earth Science Division: Status, Plans, Accomplishments,” July 27, 2015, http://science.nasa.gov/media/medialibrary/2015/08/11/FREILICH_July_SC_ESD.pdf.
TABLE 1.1 NASA FY 2016 President’s Budget Request Summary
|Budget Authority ($ in millions)||Fiscal Year|
|James Webb Space Telescope||658.2||645.4||620.0||569.4||534.9||305.0||197.5|
NOTE: The enacted fiscal year 2015 funding for NASA Earth Science is $1,772.5 million. Appropriations for fiscal year 2016 were still pending as this report went to press; however, it is expected to be between the House’s preferred $1,682.9 million and the Senate’s preferred $1,931.6 million. (Updates to this table were received during editing.)
SOURCE: NASA, “FY 2016 President’s Budget Request Summary,” https://www.nasa.gov/sites/default/files/files/NASA_FY_2016_Budget_Estimates.pdf, accessed September 23, 2016.
- Establish methodologies and/or metrics that can be used by NASA to inform strategic programmatic decisions regarding the scope and design of its observation and processing systems:
- In the context of limited resources and recognizing the programmatic and fiscal tension between the scientific benefits of providing sustained measurements on the one hand, and developing and demonstrating new or improved measurements on the other hand, determine whether a measurement(s) should be collected for extended periods, and provide guidance concerning methods to determine the appropriate balance between cost, risk, and performance when addressing continuity needs for specific measurements;
- Prioritize the relative importance of measurements that are to be collected for extended periods; and
- Identify the characteristics of, and extent to which, data gaps and/or accuracy/sampling/stability degradations are acceptable for existing and planned data sets.
In carrying out its task, the committee focused on providing a framework that would allow prioritization of measurements based on their scientific value. With respect to item 2 above, the committee’s decision framework and examples (see Chapter 3) are most applicable to choices among extended missions undertaken for research purposes aimed at quantifying global change.23 For such decisions, emphasis is on extending measurements to understand the signals of the Earth system under a changing climate and further to provide the observational basis for improved models and model projections of future climate impacts. With this specific focus, the recommended framework is intended as a new method for evaluating science-driven continuity missions and represents a complement to the existing NASA proposal evaluation processes for NASA Research Announcements24 and Earth Venture Announcements of Opportunity.25
Extended missions directed primarily at operational- or applications-based needs did not readily lend themselves to the framework here that balances scientific needs to make choices; however, applications-based priorities could be amenable to a similar approach. The committee lacked the expertise in these other areas to be able to make a suitable framework.
The committee’s quantitative framework is focused on known quantities, specifically the time series of Sun-Earth observations that have been made and used in scientific analyses. It allows an examination of the question of whether these observations to date provide information that warrants their continuation. With pertinent (different) quantified objectives in Earth science, a similar framework is equally applicable to establish priorities among new, first-of-a-kind measurements, as well as to examine operational- or applications-based measurements. Developed appropriately, the committee envisions a single comprehensive evaluation approach for both new and continuity measurements, driven by science and/or application objectives. Finally, an important practical limitation of frameworks like those presented here lies outside the science community: While the scientific priorities for future NASA science missions are guided by NRC decadal surveys, NASA also responds to congressional or executive branch input, which can result in important deviations from the scientific strategic plan.
Bindoff, N.L., P.A. Stott, K.M. AchutaRao, M.R. Allen, N. Gillett, D. Gutzler, K. Hansingo, G. Hegerl, Y. Hu, S. Jain, I.I. Mokhov, et al. 2013. Detection and attribution of climate change: from global to regional. Chapter 10 in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (T.F. Stocker, D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex, and P.M. Midgley, eds.). Cambridge University Press, Cambridge, U.K., and New York, N.Y.
23 A particular challenge in developing a metric to value the contributions of a particular measurement/observation to an application objective is the diversity of applications, which range from low-frequency, high-impact, and localized events (monitoring crustal movements of Earth to better predict mudslides, volcano eruptions, and earthquakes) to observations of the long-term, global-scale effects of climate change (monitoring sea surface height, global mass redistribution, ice sheet dynamics, temperatures and precipitation). As discussed in this report, even priori - tization of the scientific value of the more “apples-to-apples” comparisons of the latter group of climate observations is extremely challenging.
24 See Appendix C, “Proposal Processing, Review, and Selection,” in Guidebook for Proposers Responding to NASA Research Announcement (NRA) or Cooperative Agreement Notice (CAN), January 2015, http://www.hq.nasa.gov/office/procurement/nraguidebook/proposer2015.pdf.
25 See Section 7.0, “Proposal Evaluation, Selection, and Implementation,” in Draft Announcement of Opportunity, Earth Venture Mission – 2, Earth System Science Pathfinder Program, Solicitation Number NNH15ZDA008J, May 12, 2015, http://nspires.nasaprs.com/external/.
Leone, D. 2013. Hosted payload is part of NASA’s plan for maintaining climate record. Space News. October 31. http://spacenews.com/37939hosted-payload-is-part-of-nasas-plan-for-maintaining-climate-record/.
Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, and J. Huang. 2013. Anthropogenic and Natural Radiative Forcing. Chapter 8 in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (T.F. Stocker, D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex, and P.M. Midgley, eds.). Cambridge University Press, Cambridge, U.K., and New York, N.Y.
NASA. 2010. Responding to the Challenge of Climate and Environmental Change: NASA’s Plan for a Climate-Centric Architecture for Earth Observations and Applications from Space. http://science.nasa.gov/media/medialibrary/2010/07/01/Climate_Architecture_Final.pdf.
NASA. 2014 Science Plan for NASA’s Science Mission Directorate. NASA Headquarters, Washington, D.C. http://science.nasa.gov/media/medialibrary/2014/05/02/2014_Science_Plan-0501_tagged.pdf.
NRC (National Research Council). 2000. Issues in the Integration of Research and Operational Satellite Systems for Climate Research: Part I. Science and Design. The National Academies Press, Washington, D.C.
NRC. 2007. Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond. The National Academies Press, Washington, D.C.
NRC. 2008. Satellite Observations to Benefit Science and Society: Recommended Missions for the Next Decade. The National Academies Press, Washington, D.C.
NRC. 2012. Earth Science and Applications from Space: A Midterm Assessment of NASA’s Implementation of the Decadal Survey. The National Academies Press, Washington, D.C.
NRC. 2013. Review of NOAA Working Group Report on Maintaining the Continuation of Long-Term Satellite Total Irradiance Observations. The National Academies Press, Washington, D.C.
NSTC (National Science and Technology Council). 2014. National Plan for Civil Earth Observations. http://www.whitehouse.gov/sites/default/files/microsites/ostp/NSTC/national_plan_for_civil_earth_observations_-_july_2014.pdf.