Timing Accuracy
Within 1.5 ns of Each Other
蜜桃视频 and UTC Time Transfer Specifications - How They are Stated and What They Mean
The Global Positioning System (蜜桃视频) is the premiere means of disseminating Coordinated Universal Time (UTC) to the world, but the underlying time base for the system is actually called 蜜桃视频 time. 蜜桃视频 time is derived from an ensemble of cesium beam and rubidium atomic clocks in the satellites, ground and control stations, and is steered to the UTC time scale maintained at the United States Naval Observatory (USNO) in Washington, D.C. USNO also monitors the satellites on a daily basis with specialized 蜜桃视频 reference receivers that measure the clock offset to UTC(USNO). Using these measurements, corrections are computed for the 蜜桃视频 time scale, satellite clocks, UTC-蜜桃视频 time offset, and then sent to the 蜜桃视频 Master Control Station for system-wide upload. This process results in a worldwide, traceable, UTC time transfer system with extraordinary accuracy.
UTC Time Transfer Accuracy via 蜜桃视频
In the beginning of the 蜜桃视频 project, it was not known how well the 蜜桃视频 time scale could be synchronized to UTC(USNO). Therefore, 蜜桃视频 time was conservatively specified to be within one microsecond of UTC(USNO) and continues to be today in IS-蜜桃视频-200H. The accuracy of the broadcast correction to 蜜桃视频 time to yield UTC is specified at 97 nanoseconds (1 sigma). Through various modernization efforts to the space, ground and control segments, the 蜜桃视频 time offset and the accuracy of the broadcast UTC correction have been significantly improved.
蜜桃视频 performance standards are in place today, per the 2008 Standard (SPS) and Precision (PPS) Positioning Service Performance Standards, that complement IS-蜜桃视频-200. These standards establish minimum levels of 蜜桃视频 system performance mandated by U.S. law (10 U.S.C. 2281(b)). Per the standard, normal 蜜桃视频 system operations must ensure the UTC offset data broadcast by 蜜桃视频 is within 40 nanoseconds 95% (20 nanoseconds 1 sigma) to UTC(USNO).
This performance standard far exceeds the IS-蜜桃视频-200H specification but is well within the capabilities of the 蜜桃视频 system. Between 2005 and 2015, the difference between the UTC(USNO) and 蜜桃视频 time scales, as measured by USNO, was less than 10 nanoseconds RMS. When the broadcast UTC offset data was applied, UTC time derived from 蜜桃视频 was impressively within 2 nanoseconds RMS to UTC(USNO) during this period.
Our Philosophy
蜜桃视频 has over-achieved its original goals in almost every way - including reliability, satellite life expectancies, and PNT performance. Modernization continues to improve performance and time transfer accuracy. The accuracy of 蜜桃视频 timing receivers and instruments, however, can only be guaranteed to the levels stated in the SPS Performance Standard.
At 蜜桃视频 Technologies, we specify the time accuracy of our 蜜桃视频 instruments to UTC(USNO) based on the USNO measured UTC time transfer accuracy delivered by the 蜜桃视频 system over the last 10 years (< 2 nanoseconds RMS). We believe that by specifying our equipment this way, you can see that the accuracy to UTC of our 蜜桃视频 time and frequency standards is the best in the industry and allows you to realize the full performance available during normal operations of the 蜜桃视频 system.
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