GOMOS (Global Ozone Monitoring by Occultation of Stars)
The Global Ozone Monitoring by Occultation of Stars (GOMOS) Instrument on board Envisat is the newest ESA instrument aiming at ozone monitoring. It is a tool to provide altitude-resolved global ozone mapping and trend monitoring with very high accuracy, as needed for the understanding of ozone chemistry and for model validation. The primary GOMOS mission objectives are:
Measurement of profiles of ozone, NO2, NO3, OClO, temperature, and water vapor;
Day- and night-side measurement capability;
Global coverage with typically over 600 profile measurements per day;
Altitude measurement capability between the tropopause and 100 km;
Altitude resolution of better than 1.7 km.

MERIS (MEdium Resolution Image Spectrometer Instrument)
The MEdium Resolution Imaging Specrometer Instrument MERIS measures the solar radiation reflected by the Earth, at a ground spatial resolution of 300m, in 15 spectral bands, programmable in width and position, in the visible and near infra-red. MERIS allows global coverage of the Earth in 3 days.

The primary mission of MERIS is the measurement of sea colour in the oceans and in coastal areas. Knowledge of the sea colour can be converted into a measurement of chlorophyll pigment concentration, suspended sediment concentration and of aerosol loads over the marine domain.

Why measure ocean colour?
Four broad domains of applications of ocean-colour data can be identified:
the ocean carbon cycle
the thermal regime of the upper ocean
the management of fisheries
the management of coastal zones