Update on Boulder Internet Time Services and atomic time scale
jeff.s...@nist.gov
Dear colleagues,
Utility power was recently restored to the NIST Boulder campus. Assessment and repair activity is in progress, but I want to give a brief status update regarding Internet Time Services on the NIST Boulder campus. As usual, status notes per-server will be manually updated here:
Clocks and time transfer services operated from the NIST WWV/Ft. Collins and Gaithersburg, MD campuses are independent and were unaffected throughout.
Soon after the last notice, NIST facilities staff stationed on-site started a diesel generator held in reserve and activated a power transfer switch positioned to supply “second backup” power to the affected laboratory. The period without ac power (due to automatic “first backup” generator failure after 2 days of continuous operation) was about 2 hours. However, large battery banks kept all clocks and most measurement and distribution chains powered throughout. Additional quick action by NIST facility staff secured temperature control for the most sensitive clocks. We regained some monitoring ability showing that the disseminated UTC(NIST) signal likely did not deviate by more than 5 us (five millionths of a second) and appeared stable. Knowing this, I decided to keep the Boulder Internet Time Servers active until we lost monitoring or some other event caused the time scale deviation to increase significantly.
To put a deviation of a few microseconds in context, the NIST time scale usually performs about five thousand times better than this at the nanosecond scale by composing a special statistical average of many clocks. Such precision is important for scientific applications, telecommunications, critical infrastructure, and integrity monitoring of positioning systems. But this precision is not achievable with time transfer over the public Internet; uncertainties on the order of 1 millisecond (one thousandth of one second) are more typical due to asymmetry and fluctuations in packet delay.
NIST provides high-precision time transfer by other service arrangements; some direct fiber-optic links were affected and users will be contacted separately. However, the most popular method based on common-view time transfer using GPS satellites as "transfer standards" seamlessly transitioned to using the clocks at NIST's WWV/Ft. Collins campus as a reference standard. This design feature mitigated the impact to many users of the high-precision time signal.
Best wishes,
-Jeff Sherman
Project email: internet-t...@nist.gov