Thermal Design of ASTHROS

The Astrophysics Stratospheric Telescope for High Spectral Resolution Observations at Submillimeter-wavelengths (ASTHROS), is a 2.5-m balloon-borne observatory that will make the first spectrally-resolved high spatial resolution 3D map of ionized gas in Galactic and extra-galactic star forming regions via the THz fine structure lines of ionized nitrogen and other nearby spectral lines. Building on the Stratospheric THz Observatory (STO-2) and Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory (GUSTO) missions, ASTHROS, launching in 2023 will, over its 21-day Antarctic mission, map two template Galactic star forming regions and the entire disk of the M83 barred spiral galaxy at high angular resolution. The Applied Physics Laboratory (APL) will build the ASTHROS gondola and thermal control system. The latter will use a fluid loop and radiator very similar to that used by APL on GUSTO. This paper will present an overview of the thermal design of the ASTHROS gondola and telescope.