The Stratospheric TeraHertz Observatory (STO)

The structure of the interstellar medium (ISM), the life cycle of interstellar clouds, and their relationship with star formation are processes crucial to deciphering the internal evolution of galaxies. Many important key gas tracers are not observable from the ground, but are needed to understand how interstellar clouds form and dissipate and how the Galaxy is structured. STO, the Stratospheric Terahertz Observatory [1], is a Long Duration Balloon (LDB) experiment designed to address a key problem in modern astrophysics: understanding the Life Cycle of the Interstellar Medium. STO will first survey a section of the Galactic plane in the dominant interstellar cooling line [C II] (158 μm) and the important star formation tracer [N II] (205 μm) at ~1 arc minute angular resolution, sufficient to spatially resolve atomic, ionic and molecular clouds at 10 kpc. The mission goals for this survey are to: