Notice advisory to NAVSTAR users

A notice advisory to NAVSTAR users, or NANU, is a message issued jointly by the United States Coast Guard and the GPS Operations Center at Schriever Air Force Base in Colorado. NANUs provide updates on the general health of individual satellites in the GPS constellation. NANUs are typically issued approximately three days prior to a change in the operation of a GPS satellite, such as a change in orbit or scheduled on-board equipment maintenance.