How does CERN synchronize timing devices?

How CERN Syncs Time Using GPS

CERN's scientists have written detailed, complex papers explaining the inner workings of their timing systems. Signal frequencies, measurement systems and accuracy equations are just a few of the elements in CERN reports that scientists eat up and the rest of us wrinkle our brows at, including one that details the calibration of the GPS time link between CERN and LNGS.

Here's the short version: When measuring the speed of neutrinos traveling from CERN to Gran Sasso National Laboratory (LNGS), scientists need to precisely sync their instruments. So, one pulse-per-second (PPS) GPS measurements are time stamped with a measurement system called CTRI, which is based on the atomic clock that's linked to both labs and is paired to a GPS system. Those timestamps can then be compared between the two locations, and the difference in time reveals the flight time of the neutrinos. Sounds pretty simple, right?

Well, the setups still require all sorts of tests to ensure accuracy and equations to account for inevitable margins of error. The receivers CERN uses in communication with LNGS are certified by the Swiss FederalOfficeofMetrology. Because they're dealing with such precise numbers, even the position of an antenna and the cables used can throw off results.