[D66] tycho USNO

[A.O.]

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https://tycho.usno.navy.mil/

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https://en.wikipedia.org/wiki/United_States_Naval_Observatory
Time service
Atomic clock ensemble at the U.S. Naval Observatory

The U.S. Naval Observatory operates two Master Clock facilities. The
primary facility, in Washington, D.C. maintains 57
HP/Agilent/Symmetricom 5071A-001 high performance cesium atomic clocks
and 24 hydrogen masers. The alternate master clock, at Schriever Air
Force Base, maintains 12 cesium clocks and 3 masers.[30] The observatory
also operates four[31] rubidium atomic fountain clocks, which have a
stability reaching 7×10−16.[32] The observatory intends to build several
more of this type for use at its two facilities.[30] The clocks used for
the USNO timescale are kept in 19 environmental chambers, whose
temperatures are kept constant to within 0.1 degree C and whose relative
humidities (for all masers and most cesiums) are kept constant to within
1%. The timescale is based only upon the Washington DC clocks. On June
7, 2007, 70 standards were weighted in the timescale computations.[30]

The U.S. Naval Observatory provides public time service via 26[30] NTP
servers on the public Internet,[33] and via telephone voice
announcements:[34]

    +1 202 762-1401 (Washington, D.C.)
    +1 202 762-1069
    +1 719 567-6742 (Colorado Springs)

The voice of actor Fred Covington (1928–1993) has been announcing the
USNO time since 1978.[35]

The voice announcements follow the same pattern at both sites. They
always begin with the local time (daylight or standard), and include a
background of 1-second ticks. Local time announcements are made on the
minute, and 15, 30, and 45 seconds after the minute. Coordinated
Universal Time (UTC) is announced five seconds after the local time.[36]
Upon connecting, only the second-marking ticks are heard for the few
seconds before the next scheduled local time announcement

The USNO also operates a modem time service,[37] and provides time to
the Global Positioning System.