Airborne Platforms to Advance NASA Earth System Science Priorities Assessing the Future Need for a Large Aircraft (2021) / Chapter Skim
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3 The DC-8 Airborne Research Platform
3 The DC-8 Airborne Research Platform
Pages 35-56
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From page 35... ...
The need to acquire simultaneous and synchronized observations from multiple instruments in a payload has meant that research aircraft frequently operate at maximum takeoff weights. Consequently, research teams often have had to fly fewer instruments or people than they would like, reducing the scope of the research they would have liked to have achieved.
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From page 36... ...
The aircraft, built in 1969, is designated NASA 817 and is currently based at the NASA Airborne Science facility in Palmdale, California. 3.2 NASA DC-8 SPECIFICATIONS The DC-8 is a four-engine jet transport aircraft that has been highly modified from its original commercial configuration to accommodate research instruments in the main fuselage, cargo bay, and on the wings (NASA, 2015; NASA Airborne Science Program, 2021)
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From page 37... ...
In contrast, the lower stratosphere is reached routinely at maximum cruise altitude during high-latitude flights. The altitude range allows for routine flight maneuvers that vertically profile from the surface to the upper troposphere or lower stratosphere.
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From page 38... ...
data at several bands required a large platform such as the DC-8 because SAR then weighed 1,720 kg, drew 10 kW of power, and consisted of 13 electronics racks and several large antennas that covered a large area of the aircraft outer surface. NASA's DC-8 was used to collect SAR data to study Earth surface dynamics, snow and frozen ground, and geological hazards and disasters from 1988 to 2004.
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From page 39... ...
The payload is the NASA Atmospheric Tomography Mission atmospheric chemistry payload (NASA, 2020a)
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From page 40... ...
The core OIB payload consisted of four instrument suite technologies: Airborne Topographic Mapper (a laser altimetry system with several electro-optical cameras) from the NASA Wallops Flight Facility, a gravimeter from Lamont Doherty Earth Observatory, ice- and snow-penetrating radars from University of Kansas, and Digital
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From page 41... ...
SOURCE: John Sonntag, NASA Goddard Space Flight Center. Figure 3.5 Flight track map of DC-8 flights over the Antarctic continent from Punta Arenas, Chile, as part of the Operation IceBridge mission in spring 2018.
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From page 42... ...
. The third mission is the NASA atmospheric chemistry study, the Atmospheric Tomography mission (ATom)
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From page 43... ...
, multiple diverse access ports, large and complex external inlets, and a cargo bay for support equipment (e.g., pumps, gases, power supplies)
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From page 44... ...
(NASA Airborne Science Program, 2017)
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From page 45... ...
The DC-8 has a unique and powerful combination of features to support research activities in comparison to other available aircraft. These include long range, high-altitude ceiling, vertical profiling capability, large payload weight, inflight seating, in-flight communications, and instrument payload integration and operation flexibility.
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From page 46... ...
The flight range was estimated using average flight duration and a speed of 450 knots. Note: Details from several of the earliest completed DC-8 missions were not available and hence do not contribute to the statistics shown in the figure.
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From page 47... ...
While the OIB campaigns were an unanticipated airborne science need, the DC-8 was particularly valuable in enabling repeated long-duration airborne surveys of the Antarctic ice sheet and surrounding sea ice. Atmospheric composition has accounted for the most sustained use of the DC-8 with 27 field studies from 1987 to 2019.
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From page 48... ...
When atmospheric composition is combined with weather, the second-most sustained user with 14 field studies from 1992 to 2017, general atmospheric sciences have accounted for 44 percent of DC-8 flight hours. This amount is essentially equivalent to AIRSAR/Cryosphere use at 43 percent.
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From page 49... ...
Weather research, instrument development, and aeronautics also have a significant history of usage, with other areas, such as training and outreach, comprising smaller past usage. Atmospheric composition has accounted for the most sustained use of the DC-8 with 27 field studies from 1987 to 2019 followed by weather with 14 field studies from 1992 to 2017.
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From page 50... ...
Second, scientists chose smaller aircraft because the operating cost of the DC-8 is higher than that of smaller aircraft, especially when single or a few miniaturized instruments flown on individual smaller aircraft can accomplish the science objectives. Third, based on comments from committee members, workshop speakers, and the Earth system science community, scientists studying Earth's surface stopped thinking about using the DC-8 because they shared a real and widespread perception that the DC-8 would not be available for their use due to its frequent demand by atmospheric chemistry and weather.
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From page 51... ...
. The core characteristics of a replacement large aircraft are payload, range and duration, and altitude ceiling: • Instrument payload weight.
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From page 52... ...
Thus, any significant departure from the core characteristics of the DC-8 will require in prospect a careful evaluation of NASA priorities for aircraft performance and how potential changes in performance might affect achieving future mission science objectives. The success of the DC-8 missions since 1987 have relied on NASA infrastructure resources that have provided DC-8 with excellent engineering, operations, and maintenance support teams.
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From page 53... ...
These features include available instrument mounting racks, multiple diverse sample and access ports along the fuselage sides as well as the top and the bottom, external inlet mounting, multiple underwing pylons that sample unperturbed flow, and a cargo bay. Substantial payload power is available (about 80 kVA)
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From page 54... ...
Thus, any significant departure from the core characteristics of the DC-8 would require in prospect a careful evaluation of NASA priorities for aircraft performance and how potential changes in performance might affect achieving future mission science objectives. 3.6 CANDIDATES FOR A FUTURE LARGE AIRCRAFT Several operational aircraft can be considered candidates for replacing the DC-8.
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From page 55... ...
All three aircraft candidates are suitable for deep vertical profiling from near-surface to cruise altitudes (Ozoroski et al., 2020, fig.
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From page 56... ...
These operational aircraft could not only replace the DC-8 but also enhance the capability to conduct a wide variety of airborne science missions.
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