A large share of aircraft emissions occur at cruising altitude, where they significantly affect climate. While models are being developed to study these impacts, their validation is limited by scarce measurements at high altitudes. Existing efforts to use instrumented aircraft are constrained by fleet availability and limited endurance, resulting in poor temporal coverage, while measurements from satellites have poor spatial resolution. To address these limitations, this project focuses on designing a medium to high altitude, long-endurance observatory aircraft for continuous measurement of atmospheric composition, cruise emissions, and radiation for climate research. SORA (Stratospheric Observatory Research Aircraft) was developed to fulfil this mission. SORA will be capable of missions up to a duration of 60 days, and fly at cruise altitudes between 15 km and 25 km. It will generate its own power through solar panels installed on top of the wing, which also charge batteries that support night operations. The propulsion system consists of 4 electrically-powered propellers attached to the wing, which ensure zero operational emissions while fulfilling all operational requirements. Operations depend heavily on seasonal and geographical solar availability, so the aircraft was then designed to maximize its operational coverage around the planet. The final design allows full year-round operation between latitudes of -30 °N and 30 °N, with an operational map having been developed for other latitude ranges, thus allowing to know the full geographical and seasonal operational range of the aircraft. Other operational considerations include taking-off from dry aerodromes in sunny conditions, avoiding high-turbulence areas, among others. SORA will carry a series of scientific payload instruments, from spectrometers, to a LiDAR instrument and several in-situ sensors that allow it to fulfil the scientific objective of this mission. ... Read more