Walk into NASA Armstrong’s airborne science instrument preparation room in Palmdale, CA, and you will see what might appear to be an ordinary lab. This space houses things that might be found in any general-purpose laboratory—40 work benches, power strips, a fume hood, three chemical lockers, four sets of laser curtains, a shower and eyewash station, a sink, and a refrigerator. What’s missing is any kind of scientific apparatus because this is not the room where the scientific research actually occurs. Rather, this room hosts instrument teams from universities and research centers from all over the world who come here to prepare their experiments to fly.
The research occurs aboard NASA's DC-8 Airborne Science Laboratory, a highly modified Douglas DC-8 jetliner. Based at NASA Armstrong's Building 703 in Palmdale, this unique flying laboratory gathers data for experiments in support of scientific projects and community members including investigators from NASA and other federal, state, academic, and foreign institutions. The DC-8’s primary missions are sensor development, satellite sensor verification, and basic research studies of the surface and atmosphere of the Earth.
The plane was built in 1969 and used by airlines Alitalia and Braniff Airways before NASA acquired it in 1985. NASA then outfitted it for use in atmospheric science research, as well as missions related to validating instruments before they are launched on satellites and calibrating them afterward. Because it flies in Earth's atmosphere, the DC-8 is a relatively inexpensive method for testing and verifying prototype satellite instruments.
After more than a year of heavy maintenance, including an overhaul to all four engines, the DC-8 returned to the skies on January 6, 2021, to prepare for an aerosols and wind campaign, a joint effort between NASA and the European Space Agency.
NASA’s DC-8, tail number N817NA, measures 157.5 feet long, with a wingspan of 148.4 feet and a tail that is 43.5 feet high. It accommodates a flight crew of eight people and a science crew of up to 42, although it was designed for an airline capacity of 189 passengers. The aircraft has flown with as many as 38 suites of scientific instruments, weighing up to 30,000 pounds. It has a range of 5,400 nautical miles (6,200 statute miles) and can fly at mission altitudes ranging from 1,000 to 42,000 feet. The aircraft can fly for up to 12 hours, although most science missions average between six to 10 hours.
Some of the modifications on board the aircraft include zenith and nadir instrument ports; modified window ports for instrument and probe mounting; external antenna mounts; wing pylon instrument mounts; optical windows of various materials; a dropsonde delivery tube; air and aerosol sampling probes; standard 19-inch equipment racks (up to 20 racks and 25 instruments typically accommodated); a laser chiller unit; and both 400 Hz and 60 Hz power available to experimenter stations.
The DC-8 flying laboratory also houses a suite of operational aircraft and data systems, which can be customized to specific missions or science instruments. Examples include a weather radar, global positioning and inertial navigational systems, a radar altimeter, and sensors able to record total air temperature, ambient pressure, and relative humidity. The plane also has an Ethernet LAN with servers and Wi-Fi.
Missions and travels
The DC-8 has flown all over the world and conducted many types of experiments. Campaigns have included atmospheric chemistry, archaeology through synthetic aperture radar, geography, meteorology, volcanology, meteor shower observation, and spacecraft launch and reentry tracking.
“The inaugural science campaign was the 1997 Airborne Antarctic Ozone Experiment flown with instrument teams from NASA centers Ames, Langley, and JPL, as well as NOAA,” says Chris Jennison, DC-8 mission manager, Airborne Science, NASA AFRC. “The campaign confirmed the extent of the Antarctic ozone hole observed by ground science teams earlier and supported the United Nations Montreal Protocol on Substances that Deplete the Ozone Layer. Since then, the DC-8 has flown 141 science campaigns over every ocean and every continent except Africa.”
More recently, in July 2022, the DC-8 was spotted flying through a storm off the coast of North Carolina, where it was continuing its research into high ice water content—tiny ice crystals that develop in deep convective storms. These ice crystals are difficult to detect and can be hazardous to plane engines as pilots fly through and around storms. The goal of this research is for scientists to understand the conditions more fully under which ice crystals form and find ways for pilots to avoid hazardous weather that they may not even notice in the first place.
“Unlike most other dedicated scientific research aircraft, NASA’s DC-8 is a public use aircraft flying within the United States, and a state aircraft under article 3b of the Convention on International Civil Aviation (ICAO). Being entirely owned and operated by NASA, airworthiness is certified by NASA and it operates in accordance with FAA and ICAO regulations. This permits the aircraft to be reconfigured quickly between campaigns and accommodate nearly any instrument mission type conceivable,” says Jennison.
Even though the DC-8 has been in operation with NASA for nearly 40 years, there are currently no plans to replace the aircraft, says Jennison. “NASA has considered replacing aircraft, but the analysis revealed that no other aircraft or even combination of aircraft could meet the versatility and economy of the current airplane. NASA 817 was designed at a time when the tools were drafting boards, slide rules, and wind tunnels. This was before computer assisted design and manufacturing, before computational fluid dynamics and finite element analyses. As such, the DC-8 was designed with a conservatism not practiced today and as a jet airliner outlasted all of its civilian contemporaries.”