This project continues to precisely measure large-scale solar surface brightness variations across the solar disk. The PI acquires data with the Solar Disk Photometer at Big Bear Solar Observatory, principally to better understand the diffuse component of the solar irradiance variations. This is one of the main elements responsible for the long-term solar cycle modulation of the Sun's radiative output. The PI's continuation of this research will allow analysis of upcoming precision photometric measurements of the rise from solar minimum to maximum, important for understanding solar-cycle irradiance variations. Long-term irradiance variations could impact the Earth more profoundly than any other solar phenomenon.
