Expanding South Pole Telescope Science: Asteroids and Black Holes

I present an expansion of the science carried out with the 10-meter South Pole Telescope (SPT), an instrument optimized for observing at millimeter (mm) and submillimeter wavelengths with the primary science goal of characterizing the cosmic microwave background (CMB). First, I develop new uses for archival SPT data and conduct the first targeted study of asteroids in CMB survey observations. Thermal emission at mm wavelengths probes the cooler subsurface layers of asteroids, providing unique constraints on their thermophysical properties. I present the implementation of a new analysis pipeline and the successful detection of three large main belt asteroids: (324) Bamberga, (13) Egeria, and (22) Kalliope. Second, I develop new observations for SPT of the Galactic Center to target studying the variability of the black hole Sagittarius A* (Sgr A*). Characterizing the variability of Sgr A* at mm wavelengths offers insights into accretion physics and magnetic field structure. I present the development of this observing campaign and the ongoing analysis of the resulting dataset, which constitute a uniquely complete, multi-frequency, long-duration light curve of Sgr A*. Finally, I develop new methods for controlling SPT to support its participation as a part of the Event Horizon Telescope (EHT). Planned upgrades to the EHT receiver on SPT necessitate stricter pointing accuracy than typical observations with SPT, and improving our ability to point SPT accurately requires a detailed understanding of its structural imperfections and the extreme weather at the South Pole. I present the development, deployment, and testing of machine learning models that map current weather conditions to telescope drive control arguments, thereby reducing measured average pointing error by over 30%. Collectively, these efforts leverage and enhance the capability of SPT to push its scientific reach from cosmology into new areas of astronomy and astrophysics.