Long-term calibration and validation of stability of the Auger Engineering Radio Array using the diffuse Galactic radio emission

TL;DR

This study demonstrates the long-term stability of the Auger Engineering Radio Array's antennas by calibrating against diffuse Galactic radio emission over seven years, confirming minimal aging effects and supporting its use for extended cosmic ray observations.

Contribution

It introduces a novel calibration method using Galactic radio emission for long-term stability assessment of radio detectors in cosmic ray experiments.

Findings

No significant antenna aging observed over seven years

Calibration method effectively monitors detector stability

Supports extended operation of radio detection arrays

Abstract

The Auger Engineering Radio Array (AERA) measures radio emission from high-energy extensive air showers. Consisting of 153 autonomous radio-detector stations spread over $17$\,km$^2$, it detects radio waves in the frequency range of $30$ to $80$\,MHz. Accurate characterization of the detector response is crucial for proper interpretation of the collected data. Previously, this was achieved through laboratory measurements of the analog chain and simulations and measurements of the antenna's directional response. In this paper, we perform an absolute calibration using the continuously monitored sidereal modulation of the diffuse Galactic radio emission. Calibration is done by comparing the average frequency spectra recorded by the stations with predictions from seven different models of the full radio sky, accounting for the system response, which includes the antenna, filters, and amplifiers. The analysis of the calibration constants over a period of seven years shows no relevant and no significant ageing effect in the AERA antennas. This result confirms the long-term stability of the detector stations and demonstrates the possibility for a radio detector to effectively monitor ageing effects of other detectors operating over extended periods.