U.S. official time gets 4.8 microseconds slower over storm-triggered power outage

LOS ANGELES, Dec. 22 (Xinhua) -- A powerful windstorm that swept through the U.S. state of Colorado last week disrupted the power supply to more than a dozen atomic clocks responsible for maintaining the U.S. official time, causing the national time standard to slow by 4.8 microseconds, U.S. media reported Monday.

Gizmodo.com, a U.S.-based technology, science and science fiction website, cited an email sent on Dec. 19 by U.S. National Institute of Standards and Technology (NIST) supervisory physicist Jeffrey Sherman, saying that the atomic ensemble time scale at NIST's Boulder campus failed Wednesday due to a utility power outage.

According to a report by National Public Radio (NPR), since 2007, the official time in the United States has been determined by the commerce secretary, who oversees NIST, in coordination with the U.S. Navy. The national time standard, known as NIST UTC, is currently calculated by a weighted average of readings from 16 atomic clocks located across the Boulder campus.

Atomic clocks, including hydrogen masers and cesium beam clocks, rely on the natural resonant frequencies of atoms to measure time with extremely high precision.

NIST's standard time serves as a reference for critical systems such as telecommunications networks and GPS signals.

"The agency has backup generators in case the local grid fails due to, say, an unfortunate weather incident. But there wasn't a backup generator for the backup generator when, last Wednesday, a powerful windstorm knocked out the power in Boulder," Gizmodo.com reported.

Sherman disclosed that during the mass outage last week, a failure of one of the key generators caused some clocks to lose connection with NIST's measurement and distribution systems.

The lapse resulted in NIST UTC being 4.8 microseconds slower than it should have been, said NIST spokesperson Rebecca Jacobson, who explained that it takes a person about 350,000 microseconds (0.35 seconds) to blink.

As for whether the 4.8 microsecond "drift" had any impact, Sherman told NPR that the effect depends on the user. While the deviation would likely be imperceptible to the public, he said it could pose more serious consequences for applications involving critical infrastructure, telecommunications, GPS signals and more.

As of Sunday, utility power had been restored to NIST's facilities in Boulder, and assessment and repair activities are in progress, the reports said.