Antenna pattern calibration of radio telescopes using an UAV-based device

Paraboloid antenna telescopes have been used for the last 70 years to perform radio astronomy observations and their main characteristics are well known. Over the years, telescopes operated at a given facility are often modified or upgraded with new feeds or support struts, or see their immediate surrounding environment modified. The gain of such instruments needs therefore to be measured to account for these external factors. Radio astronomers typically use galactic or extra galactic sources to assess the directional pattern. However, small radio telescopes (5-6 m) might not have the proper sensitivity to observe, in good conditions, such sources at different elevations in the sky. We present in this article a brief summary of our attempt to calibrate a 6-m dish telescope used in Belgium for solar spectrography by using an Unmanned Aerial Vehicle (UAV) carrying a small emitter.