As a part of the payload of the first European Polar Platform, the GOMOS instrument has been proposed by a group of 25 scientists from six countries. It consists of a telescope feeding two spectrographs, mounted on a dedicated steerable platform. The transmittance of the atmosphere between 250 and 675 nm is measured by comparing the spectrum of a star outside the atmosphere, and through it. The ozone tangential column is determined from its UV and Chappuis band absorption. This self-calibrated method is particularly well suited for the study of ozone long term trend. The altitude of each single measurement is precisely known (± 50 m), independently of altitude uncertainties. About 25 stellar occultations per orbit, and 350 per day, spread over all latitudes can be performed from 90 km down to 15-20 km of altitude. NO2, NO3, H2O, T(z) and aerosols are also simultaneously determined, important parameters associated to the ozone equilibrium. The ability to measure ozone long-term trends is calculated.