High time-resolved measurements of ozone during high altitude flights can address many scientific question regarding stratospheric ozone depletion, exchange processes across the tropopause and potential vorticity barriers - such as the polar vortices and the sub-tropical barrier - and the microphysics of ozone in clouds. A Fast OZone ANalizer (FOZAN) was developed and installed on board of M55-Gheophysica, a stratospheric platform able to reach an altitude of more then 20 Rm. FOZAN is a joint Russian-Italian instrument and uses the chemioluminescent heterophase reaction between ozone in the airflow and a solid state sensor; the luminescence intensity is proportional to ozone concentration, and it is registered by a photomultiplier. The devices includes an automatic self-calibrator, as well as an optical modulator, pump, microprocessor unit, air valve, ozone generator, ozone destroyer, thermostabilizer. This instrument comprises an electronic unit to control the instrument performance and to process measurement data To improve the instrument sensitivity and measurement precision, synchronous digital detection and signal averaging are performed. The instrument features also a built-in calibrated ozone generator. The instrument was tested during test flights in Italy and was operated successfully during flights over mid-latitudes and Arctic region. A tropical campaign in spring '99 over the InterTropical Convergence Zone (ITCZ) took place in the frame of the THESEO project. The paper presents the design of the instrument, the result of laboratory tests as well as preliminary results of scientific flights on board of M55-Geophysica aircraft.
