Mount Lemmon Observatory (MLO), also known as the Mount Lemmon Infrared Observatory, is an astronomical observatory located on Mount Lemmon in the Santa Catalina Mountains approximately northeast of Tucson, Arizona (US). The site in the Coronado National Forest is used with special permission from the U.S. Forest Service by the University of Arizona's Steward Observatory, and contains a number of independently managed telescopes. History The MLO site was first developed in 1954 as Mount Lemmon Air Force Station, a radar installation of the Air Defense Command. Upon transfer to the Steward Observatory 1970, the site was converted to an infrared observatory. Until 2003, a radar tower operated from Fort Huachuca was used to track launches from the White Sands Missile Range in New Mexico and Vandenberg Air Force Base in California. Telescopes Below are the 8 telescopes currently operating at the observatory. The Steward Observatory Telescope is a Cassegrain reflector used for the Mount Lemmon Survey (MLS), which is part of the Catalina Sky Survey (CSS). It was built in the late 1960s and first installed at Catalina Station on Mount Bigelow, which is nearby in the Santa Catalina Mountains. It was moved to Mt. Lemmon in 1972, and then re-housed in its current location in 1975. Its original metal primary mirror performed poorly and was replaced in 1977 with a glass mirror made of Cer-Vit. It is one of the telescopes used by students at Astronomy Camp. It discovered 2011 AG5, an asteroid which achieved 1 on the Torino Scale. The UMN-MLOF (University of Minnesota Mount Lemmon Observing Facility) telescope began operating in 1970. It is a Dall-Kirkham optical/near infrared and is of the same general design as the 1.5 m Steward telescope and another at San Pedro Mártir. The original metal mirror performed poorly and was replaced with a Cer-Vit mirror in 1974. The University of California, San Diego (UCSD) was originally a partner of UMN in operating the telescope. The CSS (Catalina Sky Survey) reflecting telescope is an unusual Pressman-Camichel design and is used to provide automated follow up observations of newly discovered near-Earth objects. It was originally located at Catalina Station and was moved to MLO in 1975. It was refurbished in 2008 and placed in a new dome in 2009 before being integrated into CSS operations. The KASI robotic telescope was installed in 2003 and is the only instrument of the Mt. Lemmon Optical Astronomy