US NAVAL OBSERVATORY
The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States
Primary missionto produce PNT [Positioning, Navigation and Timing]
()for the United States Navy and the United States Department of Defens
Adde gubernandi studium: Pervenit in astra, et pontum caelo conjunxit
"Increase the study of navigation: it arrives in the stars, and marries the sea with heaven"
The author of Astronomica is neither quoted nor mentioned by any ancient writer.
The U.S. Naval Observatory operates two Master Clock facilities.
The primary master clock, in Washington, D.C.
The alternate master clock, at Schriever Air Force Base
57 HP/Agilent/Symmetricom 5071A-001 high performance cesium atomic clocks and 24 hydrogen masers.
12 cesium clocks and 3 masers.
The observatory also operates
4 rubidium atomic fountain clocks, which have a stability reaching 7×10−16