Measured Thermal Dynamics of the Haystack Radome and HUSIR Antenna

In 2010 the Haystack 37 meter reflector was replaced with a new antenna. This work presents measurements of the spatial and temporal thermal behavior of the antenna and its radome under diurnal and seasonal forcing. Values for thermal capacity and resistance of the antenna structure and radome are derived. The convective heat transfer coefficient acting on the aluminum antenna backstructure is found to be 2 to 5 W/m² -K for all instrumented member geometries. Modeling with a simple lumped-thermal-element representation is presented, which accurately matches observed temperatures. The heat and ventilation equipment and controls are demonstrated to be sufficient to keep modeled antenna gain reductions due to thermally-induced distortions <; 0.4 dB more than 90% of the time during heating season. Gain reductions during summer will be dominated by vertical stratification of air in the radome, which is shown to be associated with daylight hours and outside temperature > 15°C.