On Dec. 6, 1830, the Department of the Navy established the Depot of Charts and Instruments to care for its chronometers, charts and other navigational equipment. By 1835, it had begun chart production, and in 1838, astronomical observations and original hydrographic research began. With an expanded mission, the agency was renamed the United States Naval Observatory in 1844. Today, its mission includes determining the positions and motions of the Earth, Sun, Moon, planets, stars and other celestial objects; providing astronomical data; determining precise time; measuring the Earth's rotation; and maintaining the Master Clock for the United States.