Nanosecond-level time synchronization of autonomous radio detector stations for extensive air showers

Abstract

To exploit the full potential of radio measurements of cosmic-ray air showers at MHz frequencies, a detector timing synchronization within 1 ns is needed. Large distributed radio detector arrays such as the Auger Engineering Radio Array (AERA) rely on timing via the Global Positioning System (GPS) for the synchronization of individual detector station clocks. Unfortunately, GPS timing is expected to have an accuracy no better than about 5 ns. In practice, in particular in AERA, the GPS clocks exhibit drifts on the order of tens of ns. We developed a technique to correct for the GPS drifts, and an independent method is used for cross-checks that indeed we reach 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. The relative 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 real time 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 relative timing offsets between radio detector stations. We demonstrate with a combined analysis that the two 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 GPS clock drifts in each individual event measured by AERA.

arXiv comment26 pages. Replaced with published version. Added journal reference and DOI

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• Design and Initial Performance of the Prototype for the BEACON Instrument for Detection of Ultrahigh Energy Particles
• Self-triggered radio detection and identification of cosmic air showers with the OVRO-LWA
• Scalable and Passive Wireless Network Clock Synchronization
• Final results of the LOPES radio interferometer for cosmic-ray air showers
• Timing calibration and spectral cleaning of LOFAR time series data
• Expected performance of air-shower measurements with the radio-interferometric technique
• The Radar Echo Telescope for Cosmic Rays: Pathfinder Experiment for a Next-Generation Neutrino Observatory
• Radio Detection of ultra-high-energy Cosmic-Ray Air Showers
• A nanosecond-duration radio pulse originating from the defunct Relay 2 satellite
• Latest results of the Tunka Radio Extension (ISVHECRI2016)
• Air Shower Detection by Arrays of Radio Antennas (ISVHECRI 2018)