ERS - ENVISAT SYMPOSIUM Gothenburg 16-20 October, 2000 GOMOS Level 2 processing chain verification (step by step) : Check functionality of the level 2 processing chain using real measurements Coherency with model - climatology verification : Verification of the coherency using forward models (real star spectra, climatology models) Tuning of Level 2 processing parameters : analyse and validate the level 2 products tuning of the parameters of the level 2 processing chain to identify the new initial operational configuration (iterative tuning).