U.S. Naval Observatory Alternate Master Clock

The U.S. Naval Observatory Alternate Master Clock at Schriever Air Force Base.  It is used to check the time being distributed by the Global Positioning Satellites.  The clock here showed 23:59:60 Saturday, January 1, 2006, reflecting the addition of the first leap second in seven years.

Caption:
The U.S. Naval Observatory Alternate Master Clock at Schriever Air Force Base.
Type: Photograph
Image Date: January 1, 2006
Image Taken: 2nd Space Operation Squadron's Operations Center, Schriever Air Force Base, Colorado, United States
Credit: U.S. Air Force
Origin: United States Air Force
Creator: Donald S. Branum
060104-F-3966R-005
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The U.S. Naval Observatory Alternate Master Clock at Schriever Air Force Base.