# Calibration of the LOFAR low-band antennas using the Galaxy and a model of the signal chain

## TL;DR

This paper presents an improved calibration method for LOFAR low-band antennas using Galactic emission and a detailed signal chain model, enhancing spectral analysis accuracy for cosmic ray studies.

## Contribution

The study introduces a new calibration approach combining Galactic emission data and a detailed signal chain model for LOFAR antennas, achieving better spectral accuracy.

## Key findings

- Achieved a systematic uncertainty of 13% in calibration.
- Improved spectral shape agreement between data and simulations.
- Provided an absolute energy scale for cosmic ray measurements.

## Abstract

The LOw-Frequency ARray (LOFAR) is used to make precise measurements of radio emission from extensive air showers, yielding information about the primary cosmic ray. Interpreting the measured data requires an absolute and frequency-dependent calibration of the LOFAR system response. This is particularly important for spectral analyses, because the shape of the detected signal holds information about the shower development. We revisit the calibration of the LOFAR antennas in the range of 30 - 80 MHz. Using the Galactic emission and a detailed model of the LOFAR signal chain, we find an improved calibration that provides an absolute energy scale and allows for the study of frequency-dependent features in measured signals. With the new calibration, systematic uncertainties of 13% are reached, and comparisons of the spectral shape of calibrated data with simulations show promising agreement.