An improved high altitude ultrasonic anemometer

Abstract

This paper describes a sonic anemometer for low pressure (∼10mbar) environments. The technology is being developed as a high accuracy 3-D wind measurement system for the surface of Mars and stratospheric balloons. Applications include climate research, balloon navigation, and detection of energetic events through infrasonic atmospheric gravity waves. The device was constructed from an ST 32 bit Nucleo microcontroller and a custom daughter board that interface with high performance application specific amplifiers and multiplexers. Total power draw is 1.5 W. The sensor head uses narrowband commercial ultrasound transducers operating near 40 kHz at voltages below 30 Vpp. The total mass of the head is 180 g with a volume 15 cm on a side. The resulting system can take speed of sound and 3-axis flow velocity data at 0.4 Hz with 10 cm/s RMS fluctuation. Bell jar testing demonstrated operation to −5 oC and 10 mbar. A balloon launch to 32 km will occur before the meeting and will result in the first wind measurements at this altitude with a digital sonic anemometer. We will report on results and compare to inertial and GPS. [Work supported by NASA-NNX16AJ24G and NASA-80NSSC20M0007. Thanks to the NASA Wallops Balloon Programs Office for technical support.]