A Thermal Anemometer for the Mars Meteorological Sensor Network

Abstract

Details of the design and simulation of a thermal micro anemometer intended for Mars meteorological measurements are presented. The device consists of a double sided anemometer formed on thermal isolation aerogel. Thermal input to the device is provided by a set of Pt hot films distributed evenly in an octagonal area of an AlN substrate. A thin film resistance-temperature detector (RTD) is coupled to the edge of each heater for temperature reading as the thermal distribution on the substrate changes with wind speed and direction. Finite element modeling of the device showed that the temperature gradient between the upstream and downstream RTDs increases with increasing distance from the hot film and decreases with increasing wind speed. Evaluation of the device transfer function suggested that it could be suited for measuring wind speeds of up to 60 m/s with a resolution in the order of 1 m/s. These characteristics are comparable with the requirements of past Mars missions. The configuration of the device allows also the evaluation of the out-of-plane component of wind speed and of the wind direction. It was found that quadratic fitting function based on the highest temperature readings of the distributed RTDs could be used to determine more accurately the wind direction.