The National Solar Observatory (NSO) is a United States public research institute that studies the Sun. It is headquartered in Boulder, Colorado, with major sites in Tucson, Arizona and Maui, Hawaii. The NSO is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation (NSF). The NSO designs, builds, and operates ground-based telescopes and instruments to study the Sun and its effects on Earth. The NSO also provides data and tools to the scientific community to support solar research.