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As June 30 Nears, Leap Second Looms

June 22, 2015  - By


The world’s clocks will be adjusted by one second on June 30, when a leap second will be inserted into Coordinated Universal Time (UTC), the standard international time scale.

In theory, all UTC clocks should insert a second labeled 23h 59m 60s (the leap second) following one labeled 23h 59m 59s UTC. This is equivalent to having all of the clocks in the world stop for one second at that time, as explained in May’s Expert Advice column.

Several legacy GPS receivers immediately and incorrectly applied a leap second correction as early as January, or showed incorrect leap-second-pending data when queried due to an incorrect interpretation of the GPS specification by the firmware programmers of those GPS receivers, according to Jackson Labs Technologies.

To help affected industries prepare, the DHS National Coordinating Center for Communications issued guidance with a paper titled “Best Practices for Leap Second Event Occurring on 30 June 2015.”

The financial market has prepared for potential disruptions. The adjustment could present technical difficulties for traders and exchanges, as some computers might not be programmed to account for the adjustment.

One company preparing is Racelogicwho makes the LabSat simulator. Racelogic will be recording the leap second as it happens and will then have the scenarios available for customers to replay. A variety of recordings will be taken: GPS, GLONASS, and BeiDou constellations will each be captured as a single channel, and also as a simultaneous triple-constellation recording. These will then be available to use with the LabSat.

Jackson Labs has released new firmware versions for various products that address any potential issues for the pending and future leap second events, and that add a number of additional commands to query and handle leap second events.

Precise Time and Frequency, Inc., has published a paper, “Phase Error Correction — Precision versus Speed,” which describes a technique for rapidly eliminating very large phase offsets (up to 0.5 seconds) between two 1 pulse per second pulses. The change is achieved without a sudden step change (which can be unwelcome in numerous applications) while retaining the ability to tune the phase with high precision (resolution of 0.006 pico seconds) once the large error is eliminated.

“Like many novel ideas, the simplicity of this technique belies its effectiveness,” according to the paper. “With hindsight it seems like an obvious solution; however, the engineering mind is trained to know that to generate a one-second pulse from a reference frequency (in this case 10 MHz), it must be divided by the frequency itself, and the concept of an ‘incorrect’ divisor is not necessarily so obvious. In this case, however, the technique provides an ideal solution that reduces the phase-lock capture time from something that would be intolerable to a very acceptable time period.”

Download the paper at this link.

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