Different experiments use different techniques to detect and reconstruct cosmic-ray events, yielding
different energy scales. Having a method to compare the energy scales of different experiments
with minimal uncertainty is necessary in order to make meaningful comparisons of their spectra
and composition measurements, which are used to create global models of cosmic-ray sources,
acceleration and propagation. Comparing energy scales has proven to be difficult, given that
uncertainties on energy measurements depend on the location, technique and equipment used.
In this contribution we introduce a new radio-based technique which will be used to build a
universal cosmic-ray energy scale. Radio detection provides a measure of the radiation energy in
air showers, which scales quadratically with the electromagnetic energy. Once the local magnetic
field strength is taken into account, radiation energy can be directly compared at different locations.
A portable array of antennas will be built and deployed at various experiments, measuring radiation
energy in conjunction with the host experiments’ traditional air shower measurements. The energy
measured at each location can then be directly compared via the contemporaneous radiation energy
measurements. Using radiation energy to compare the energy scales eliminates uncertainties
due to measurements being made at different locations, and using the same array at each site
eliminates the uncertainties associated with the equipment and calibration. This will allow for
a cross-calibration of the energy scales of different experiments with minimal uncertainty. Here
we present the technique and report on the status of a prototype array that began taking data in
January 2021.
