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Introduction
1.1 BACKGROUND CONTEXT
The Earth system is a complex combination of solids, liquids, gases, and living organisms, all interacting with each other and changing. Humans are now so numerous that this complex Earth system, in addition to its natural variability, is showing change in response to human activities—change that is not necessarily to the benefit of humans or their environment. Avoiding Earth system shifts detrimental to humans and a sustainable environment and allowing humans and ecosystems to thrive requires accurate predictions of the future Earth system state based on different scenarios of human activity. These predictions, which require observations, can then provide the basis for modifications to those activities. Accurate predictions require developing the understanding that is required to make predictions—that is, understanding Earth system predictability, which comes only from fundamental, curiosity-driven, and applied research in Earth system science.
This report focuses on the airborne observation component of an integrated approach to Earth system science research, particularly that of the National Aeronautics and Space Administration (NASA). NASA maintains a more diverse and extensive aircraft fleet for Earth system science research than any other U.S. federal agency or individual country. Observations by instruments on its many aircraft have made discoveries and resolved questions in critical Earth system science areas over land and ocean, and in the atmosphere. Among the array of NASA aircraft, NASA’s large1 aircraft have had a unique and substantial role in these research successes and the advancement of Earth system science and prediction.
Acquired in 1987, the NASA Douglas DC-8-72 (hereafter DC-8) has ably fulfilled a unique and important role in NASA’s airborne fleet as a heavy-lift, long-duration aircraft capable of flying at altitudes from the planetary boundary layer to the upper troposphere and, in some regions, the lower stratosphere for the past three decades. However, the DC-8 is becoming more difficult to maintain and is nearing the end of its useful life. As a result, it is scheduled to be retired in the 2025 time frame. At the same time, technological advances have enabled size, weight, and power reductions for some instruments that used to require a large aircraft. In other cases, the DC-8 has provided
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1 For this report, “large” refers to an aircraft like the NASA DC-8, which is defined by a unique combination of endurance, range, payload weight and power capacity, flexibility in payload composition, altitude range and ceiling, and space to accommodate many investigators. See Chapter 3 for more specifications.
the opportunity to carry more instruments on a single aircraft in order to answer emerging science questions. NASA now has to decide if a large aircraft, with capacity, power, long-duration, and vertical profiling capabilities similar to the DC-8's, is essential for achieving NASA’s future Earth system science research goals.
1.2 COMMITTEE’S TASK
At the request of NASA, the National Academies of Sciences, Engineering, and Medicine (the National Academies) established the Committee on Future Use of NASA Airborne Platforms to Advance Earth Science Priorities to inform the agency about future needs for a large aircraft. Specifically, the committee was charged with evaluating whether a long-range, heavy-lift, large aircraft that would replace the DC-8 is needed to address the science questions posed in the 2017 Earth Science and Applications from Space Decadal Survey, or ESAS (NASEM, 2018a), and to evaluate the potential for alternative airborne platforms to address the science questions. The full Statement of Task is provided in Box 1.1.
The committee approached this task by examining the role of airborne platforms,2 including use of long-range and heavy-lift aircraft, among the components of an integrated observing strategy for Earth system science that would address priority questions associated with the science and applications priority areas identified in ESAS. These science areas include coupling of the water and energy cycles; physics and dynamics for improving weather forecasts; air quality and atmospheric chemistry—chemistry coupled to dynamics; ecosystem change—land and ocean; sea level rise in a changing climate and coastal impacts; and surface dynamics, geological hazards, and disasters. Building on this, the committee also considered how large aircraft can enable expanding use of interdisciplinary research approaches. This report highlights extreme precipitation and flooding and wildland fire as two examples where a large aircraft will be critical to improving knowledge and informing societal responses. Other elements of the charge, including consideration of airborne platforms other than aircraft, technology advancements, and workforce development, are also addressed.
To carry out its task, the committee conducted a virtual public workshop on July 29-31, 2020, with a series of panel discussions where it gained input on each of the science areas from the broader research community. In addition, the committee met regularly in closed session (virtually) over the course of 11 months leading up to and after the workshop to develop this report. Though the DC-8 aircraft is no longer one that is currently produced, the committee solicited input and considered data on historical usage of this aircraft (some of which was provided directly by NASA and is summarized
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2 For this report, airborne platforms include piloted aircraft, uncrewed airborne systems, and balloons.
in this report) and used this to inform its deliberations on recommendations to NASA on future aircraft and other airborne platforms.
1.3 REPORT BLUEPRINT
Chapter 2 begins this report with an overview of the role of airborne platforms in Earth system science to orient readers to how airborne observations fit into integrated Earth system science research, key issues with current airborne science, evolution of instrumentation, and the composition of the current U.S. airborne fleet. Chapter 3 then provides an overview of the evolution of DC-8 usage and how long-range, heavy-lift aircraft have enabled science. Chapter 4 discusses how airborne platforms have advanced science within the six focal science areas listed earlier in this chapter and whether a large aircraft is needed in the future to address the ESAS questions. Chapter 4 also discusses the importance of expanding interdisciplinary research strategies and how a large aircraft can enable that science. Contributions of the DC-8 to workforce training and development and consideration of future needs and opportunities in this space are discussed in Chapter 5. Overarching conclusions and recommendations are provided in Chapter 6.