An external calibrator for hydrogen observatories

The External Calibrator for Hydrogen Observatories (ECHO) is an ongoing project to develop precision calibration sources for wide-field, low frequency, radio arrays such as the Murchison Widefield Array and the Hydrogen Epoch of Reionization Array which target 21cm radiation from primordial times. The accuracy of existing antenna beam models have been found to be a key factor limiting the realized sensitivity of the analysis pipelines. The precision required motivates us to go beyond applying a single model to each antenna in the array characterization and instead measure the response of the as-built system. We have developed a system for mapping the response pattern with a drone-mounted transmitter. Here we report a first series of tests, including our first test maps of known calibration standards and a second test mapping an MWA tile.