Streamsonde is proposed as the world’s lightest weather sonde, that can be launched out of airplane or balloon to measure atmospheric conditions off ground at unprecedented accuracy. The sonde carries also sensors for air quality measurements, as new technologies have become very light in the last years. Therefore, Streamsonde is able to measure not only the standard meteorological variables (e.g. pressure, temperature and relative humidity) but also additional air quality parameters (e.g. ozone, nitrogen dioxide) which so far require separate soundings. FM-radio based data transmission is planned to be used, while GNSS sensors installed on the sonde allow to tag accurately the measurements when the sonde floats through the atmosphere.