The ozonesonde is a lightweight, balloon-borne instrument. It is a combination of a conventional meteorological radiosonde and an electrochemical concentration cell (ECC) that senses ozone as is reacts with a dilute solution of potassium iodide to produce a weak electrical current proportional to the ozone concentration of the sampled air. As the balloon carrying the instrument package ascends through the atmosphere, the ozonesonde transmits data via a radio link to a ground receiving station. Data from an ozonesonde are ozone concentration and standard meteorological quantities such as pressure, temperature and humidity. Typically the balloon will ascend to altitudes of about 40 km before it bursts.