Wind Noise Mitigation of Infrasound Sensor Payloads on High Altitude Balloons

A major limitation of recording infrasound sources via ground-based sensors is wind noise. An approach that mitigates this limitation is the use of balloon-based sensors. Heliotropes, a type of high-altitude solar-powered balloon, float within the lower stratosphere and are regularly used to study infrasound sources due to the minimal relative speed between the air and the balloon (i.e., low wind). However, to determine the direction of arrival for a signal, there must be at least two sensors with a separation comparable to the wavelength. The separation between the balloon and the sensors result can result in higher relative wind speeds compared to the balloon since the sensors are being pulled towed by the balloon. The increased wind noise can obscure infrasound signals of interest. This has motivated the current study aimed at identifying a compact, lightweight infrasound windscreen that can be deployed on high-altitude balloons. Variations of a previous design, termed SunFoam, are evaluated with ground and flight testing. This includes a flight where the use of the SunFoam windscreen reduced the noise floor allowing for the detection of microbaroms.