A stratospheric ozonesonde has been developed which utilizes the chemiluminescent principle for the measurement of ozone concentration after deployment from an Arcas rocket vehicle. A sample bottle-empties as it is carried to low pressures of high altitudes and is ejected above the stratopause level. Flow into the bottle results from the differential pressure as the instrument descends on a drag parachute. Ozone in the environment flows over the detector and the photons produced by the destruction of ozone molecules on the chemiluminescent material are monitored by a photomultiplier tube. The output signal is transmitted on a carrier frequency of 1680 megacycles and received at the ground by AN/GMD-l equipment. The instrument is calibrated with known concentrations of ozone and flow rate. Results of one firing are.