Within the BEXUS 12 campaign a combined high-resolution measurement of small scale fluctuations of wind and temperature was performed, using several sensors located at different sides of the gondola. For the wind measurement a constant temperature anemometer (CTA) is used. This instrument utilizes the cooling effect of a small (5µm diameter) wire which is held at a constant temperature. The voltage required for keeping the temperature constant gives the wind speed. Temperature is
measured with a resistance thermometer in form of an even thinner (1µm) wire, see picture below. The resistance is directly proportional to temperature. Due to the small heat capacity of the wire, a high resolution and a quick response time can be achieved.
Both sensors are sampled with 8 kHz which corresponds to a vertical resolution of less than a millimeter, assuming a mean ascend rate of 5 m/s. To distinguish whether a given sensor might be affected by gonola-induced turbulence, local flow direction relative to the gondola was recorded with a wind vane. Additionally sensors for attitude measurement and housekeeping were on board. The combined instruments were far too heavy to fly with a small balloon as can be launched from Kühlungsborn. The photograph below shows the 160kg payload (another experiment was on the gondola as well) just before launch.
Data analysis is ongoing.