The Atomic Clocks - More than 20 atomic clocks are measured and tracked at the NIST laboratories in Boulder, Colorado, and as noted earlier, from 10 to 15 atomic clocks are typically included in the time scale ensemble. The following sections briefly describe the various elements of UTC(NIST), including the atomic clocks, the measurement systems, the ATI time scale algorithm and the free-running TA(NIST) time scale, and the realization and generation of UTC(NIST) as a physical signal.
Leap seconds are incorporated into the UTC(NIST) time codes but do not change the physical signals (5 MHz and 1 PPS). Rate adjustments applied to TA(NIST) generate UTC(NIST) and keep the time |UTC – UTC(NIST)| small. TA(NIST) is analogous to EAL, generated from measurements of free-running atomic clocks at NIST. TAI is identical to UTC except for an integer number of seconds, known as leap seconds, that UTC within 0.9 seconds of astronomical time scales. The rate of EAL is compared to measurements of the SI second (realized by primary/secondary atomic frequency references) to obtain rate corrections that are applied to EAL to generate TAI.
#WHATS THE UTC CLOCK FOR IN RUNESCAPE FREE#
EAL is the BIPM’s time scale of the world’s free running atomic clocks. When necessary, leap seconds are inserted into UTC and into the UTC(NIST) time codes, but do not change the physical UTC(NIST) signals.įigure 1. A reference plane for the 1 PPS timing signals indicates the point where the signals are exactly “on time”. The physical signals, in the form of one pulse per second (PPS) signals for time, and 5 MHz signals for frequency are distributed through various distribution amplifiers in the NIST laboratories. The difference, once again, is that UTC(NIST) produces physical signals, and that UTC does not. ALGOS computes a free-running atomic time scale called EAL, that is similar to TA(NIST). The BIPM utilizes a time scale algorithm called ALGOS that is similar to AT1. This process, shown in Figure 1, is again similar to the way that UTC works. UTC(NIST) is generated by applying coordination adjustments to TA(NIST) so that that UTC(NIST) agrees in time (synchronization) and in frequency (syntonization) with UTC.
However, TA(NIST) is not the same thing as UTC(NIST), it is a free-running time scale that is not adjusted. For example, it is designed to keep running if any of the individual clocks fail, and it is also designed to be more stable than any of the individual clocks. TA(NIST) has both reliability and performance advantages over any individual clock. The AT1 algorithm then generates a composite oscillator, called TA(NIST), that serves as the primary oscillator for the UTC(NIST) time scale. The clocks are continuously measured to determine their relative stability, and the measurement data is input to a time scale algorithm, called AT1. UTC(NIST) works by continuously operating its ensemble of atomic clocks under carefully controlled environmental conditions.
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