Nanosecond-level time sinchronization of autonomous radio detector stations using a reference beacon and commercial airplanes.

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

JOURNAL OF INSTRUMENTATION

IOP PUBLISHING LTD

Lugar: Londres; Año: 2016 vol. 11 p. 1018 - 1018

1748-0221

To exploit the full potential of radio measurements of cosmic-ray air showers at MHzfrequencies, a detector timing synchronization within 1 ns is needed. Large distributed radio detectorarrays such as the Auger Engineering Radio Array (AERA) rely on timing via the Global PositioningSystem (GPS) for the synchronization of individual detector station clocks. Unfortunately, GPStiming is expected to have an accuracy no better than about 5 ns. In practice, in particular inAERA, the GPS clocks exhibit drifts on the order of tens of ns. We developed a technique tocorrect for the GPS drifts, and an independent method is used to cross-check that indeed we reacha nanosecond-scale timing accuracy by this correction. First, we operate a ?beacon transmitter?which emits defined sine waves detected by AERA antennas recorded within the physics data. Therelative phasing of these sine waves can be used to correct for GPS clock drifts. In addition to this,we observe radio pulses emitted by commercial airplanes, the position of which we determine in realtime from Automatic Dependent Surveillance Broadcasts intercepted with a software-defined radio.From the known source location and the measured arrival times of the pulses we determine relativetiming offsets between radio detector stations. We demonstrate with a combined analysis that thetwo methods give a consistent timing calibration with an accuracy of 2 ns or better. Consequently,the beacon method alone can be used in the future to continuously determine and correct for GPSclock drifts in each individual event measured by AERA.