A radiosonde is a small instrument package attached to a weather balloon. As the balloon ascends, the radiosonde takes a vertical profile of the atmosphere (up to ~30km), recording temperature, atmospheric pressure, relative humidity and wind velocity. A radio transmitter then transfers the data collected during the launch back to a computer for processing. These measurements serve as a reliable source for satellite data validation, and are the fundamental backbone for weather forecasting and atmospheric modeling. The Vaisala Radiosonde RS92-SGP measures temperature, atmospheric pressure, and relative humidity. Figure 1 shows an image of the RS92-SGP unit with each component identified.
The temperature sensor is a metallic rod. The resistance of the rod changes as a function of temperature. The humidity sensor is comprised of a heated twin, thin film capacitor. Capacitance of the sensors is changed as they absorb and diffuse water vapor. The sensor is comprised of twin sensors to prevent ice build up by heating one sensor while the other takes measurements (Vömel et. al. 2007). The GPS sensor is used to find wind speed and direction. Finally, the instrument is equipped with a silicon capacitive pressure sensor.Image description credit Jaime C.Compton