Tortugas Mountain Observatory, operated by New Mexico State University on Tortugas Mountain near Las Cruces, was founded in 1963 under Clyde Tombaugh. Built for planetary observation, it began work with a single telescope before its main building was completed, then expanded with another dome and several instruments, including a 0.61-meter reflecting telescope installed in 1967, the largest ever at the site. After 1990, that telescope was the only one reported in operation and was used in the 1990s to monitor Jupiter and Saturn. Regular use ended around 1999 or 2000, but the observatory returned to service in 2008 and revival efforts began in 2010.