OSAS-B: A Balloon-Borne Terahertz Spectrometer for Atomic Oxygen in the Upper Atmosphere

The oxygen spectrometer for atmospheric science on a balloon (OSAS-B) is the first 4.7-THz heterodyne spectrometer on a stratospheric balloon. It has been developed for remote sensing of the 4.7-THz emission of neutral atomic oxygen in the mesosphere and lower thermosphere of the Earth. OSAS-B comprises a heterodyne receiver based on a hot-electron bolometer mixer and a quantum-cascade laser as local oscillator. The high sensitivity of the superconducting detector and the large resolving power of approximately $1\times 10^{7}$ enable the detection of subtle signatures of radiation transport and high-altitude winds in the measured spectra. The first flight of the instrument took place on September 7th, 2022 from Esrange, Sweden.