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Leap second keeps Schriever, world on time

SCHRIEVER AIR FORCE BASE, Colo. -- We all know what leap year is - the day in February that comes every four years to keep our calendar on track with the Earth's revolution around the sun - but how many know of the leap second?

Leap second is essentially the same thing. Periodically, one second will be added to the Master Clock in Washington D.C. and the Alternate Master Clock, located here at Schriever Air Force Base, to keep our clocks on track with the Earth's naturally slowing rotation.

Members of the U.S. Naval Observatory here added one second to the Coordinated Universal Time (UTC) on the Alternate Master Clock June 30 and will continue to manage and adjust components to ensure seamless support to their customers worldwide.

"When the Earth's rotation gets out of sync with the clocks by .9 seconds, we put a leap second in to account for it," said Bill Bollwerk, Department of Defense Deputy Precise Time/ Time Interval Manager.

The addition of leap seconds is vitally important, as it aligns the Earth with the Celestial Reference Frame (stars and spacecraft); this ties systems such as Global Positioning System to the Earth to ensure the receiver provides the correct location on the surface of the Earth.

For the 2nd Space Operations Squadron, this means careful planning is required in order to ensure the GPS mission is not impacted.

First Lt. Sara Holman, 2 SOPS navigation payload analyst, has been tracking and planning for leap second since its announcement.

"We input the code for leap second in January so our systems would account for it. Today is a matter of ensuring the leap second occurred within the Navigation system," said Holman.

Each time a leap second occurs, there is potential for system impacts. However, proper planning and accounting for the event mitigates that risk.

"The last leap second had many commercial impacts," said Bollwerk. "Airline reservation systems crashed stranding passengers, computer systems were impacted and some social media sites went down."

Most GPS receivers are automated and programmed to account for leap seconds, so most commercial users shouldn't have a problem.

"As long as the receiver is made within the interface specifications established by the GPS program, they shouldn't have a problem with the leap second," said Bollwerk.

Because the addition of leap seconds is based off of the Earth's rotation, the number of times it happens fluctuates and is not predictable more than six months in advance.

"The frequency of the addition of leap seconds varies, but we expect it to increase in the future," said Bollwerk.

For now, rest assured the U.S. Naval Observatory is on the clock, ensuring the world's clocks are synchronized and right on time.
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