The 8.2-foot (2.5-meter) primary mirror on NASA's Astrophysics Stratospheric Telescope for High Spectral Resolution Observations at Submillimeter-wavelengths mission, or ASTHROS, is one of the largest to ever fly on a high-altitude balloon. The lightweight mirror, shown here, is coated in gold and nickel to make it more reflective in far-infrared wavelengths. NASA contracted Media Lario, an optics company in Bosisio Parini, Italy, to design and produce ASTHROS' full telescope unit, including the primary mirror, a secondary mirror, and supporting structure (called the cradle). The mirror is pictured at Media Lario. The mission's main science goal is to study stellar feedback, the process by which living stars disperse and reshape clouds of gas and dust that may eventually form new stars. Feedback regulates star formation in many galaxies, and too much can halt star formation entirely. ASTHROS will look at several star-forming regions in our galaxy where feedback takes place, and at distant galaxies containing millions of stars to see how feedback plays out at large scales and in different environments. https://photojournal.jpl.nasa.gov/catalog/PIA25166