Drone-Based Antenna Beam Calibration in the High Arctic

Abstract

Precision calibration is a critical requirement for future ultra-low-frequency observations of the early universe. The Array of Long Baseline Antennas for Taking Radio Observations from the Seventy-Ninth Parallel (ALBATROS), a radio interferometer located in the Canadian high Arctic, is designed to map Galactic foreground emission as a pathfinder for these future experiments. Accurate antenna beam characterization at these frequencies is therefore essential, yet remains uniquely challenging. We present PteroSoar, a custom-built drone platform equipped with a calibrated radio-frequency transmitter that enables controlled, in-situ measurements of low-frequency antenna beams. As an initial demonstration, we produce a two-dimensional beam map of an ALBATROS antenna at 50~MHz to a precision of approximately $10\%$ near zenith. We identify the dominant sources of systematic uncertainty, including timing imprecision, and outline hardware and software improvements that are expected to reduce beam measurement uncertainties to below $5\%$. This target is sub-dominant to the $\sim 20\%$ amplitude variability introduced by ionospheric scintillation at these frequencies, providing a practical pathway toward precision beam calibration for ALBATROS and other ultra-low-frequency radio experiments.