Beam calibration of radio telescopes with drones
  We present a multi-frequency far-field beam map for the 5m dish telescope at
the Bleien Observatory measured using a commercially available drone. We
describe the hexacopter drone used in this experiment, the design of the flight
pattern, and the data analysis scheme. This is the first application of this
calibration method to a single dish radio telescope in the far-field. The high
signal-to-noise data allows us to characterise the beam pattern with high
accuracy out to at least the 4th side-lobe. The resulting 2D beam pattern is
compared with that derived from a more traditional calibration approach using
an astronomical calibration source. We discuss the advantages of this method
compared to other beam calibration methods. Our results show that this
drone-based technique is very promising for ongoing and future radio
experiments, where the knowledge of the beam pattern is key to obtaining
high-accuracy cosmological and astronomical measurements.
