NASA Douglas DC-8-72 "Airborne Science Laboratory" N817NA returned to Lajes in the Azores on February 15, 2017. The aircraft will remain at Lajes until February 18.
The same aircraft had previously deployed to Lajes in August 2016 to conduct scientific research missions.
NASA describes the aircraft's mission and capabilities as:-
The aircraft...is used to collect data for experiments in support of projects serving the world's scientific community. Federal, state, academic and foreign investigators are among those who use NASA’s DC-8.
Data gathered with the aircraft at flight altitude and by remote sensing have been used for studies in archaeology, ecology, geography, hydrology, meteorology, oceanography, volcanology, atmospheric chemistry, cryospheric science, soil science and biology.
Four types of missions are flown with the DC-8: sensor development, satellite sensor verification, space vehicle launch or re-entry telemetry data retrieval and optical tracking, and basic research studies of Earth's surface and atmosphere.