The Stratospheric TeraHertz Observatory (STO) is a NASA funded, Long Duration Balloon (LDB) experiment designed to address a key problem in modern astrophysics: understanding the Life Cycle of the Interstellar Medium (ISM). STO will survey a section of the Galactic plane in the dominant interstellar cooling line [C II] (1.9 THz) and the important star formation tracer [N II] (1.46 THz) at ~1 arc minute angular resolution, sufficient to spatially resolve atomic, ionic and molecular clouds at 10 kpc. STO itself has three main components; 1) an 80 cm optical telescope, 2) a THz instrument package, and 3) a gondola . Both the telescope and gondola have flown on previous experiments [2,3]. They have been reoptimized for the current mission. The science flight receiver package will contain four [CII] and four [NII] HEB mixers, each with its own digital spectrometer. The first engineering test flight of STO was from Ft. Sumner, NM on October 15, 2009. Test flight instrumentation was used to evaluate STO's ability to point and track using gyroscopes/star cameras with a loadvarying, cryogenic system onboard. The science flight receiver electronics and control system were also tested.