Searches after Gravitational Waves Using ARizona Observatories (SAGUARO): System Overview and First Results from Advanced LIGO/Virgo’s Third Observing Run

National Science Foundation [AST-1909358, AST-1908972, NSF PHY-1748958, PHY1607611]; NSF [AST1821987, AST-1821967, AST-1813708, AST-1813466, AST-1814782, AST-1813825, AST-1518052]; Packard Foundation; GRAvitational Wave Inaf TeAm (GRAWITA); NASA grant [NNG17PX03C]; Gordon & Betty Moore Foundation; Heising-Simons Foundation; David and Lucile Packard Foundation; Premiale LBT 2013; National Science Foundation under CAREER award [1455090]; Data7: UA's Data Science Institute; Dunlap Institute at the University of Toronto; Canadian Institute for Advanced Research (CIFAR); state of Arizona