Photometric stability analysis of the Exoplanet Characterisation Observatory

Photometric stability is a key requirement for time-resolved spectroscopic observations of transiting extrasolar planets. In the context of the Exoplanet Characterisation Observatory (EChO) mission design, we here present and investigate means of translating space-craft pointing instabilities as well as temperature uctuation of its optical chain into an overall error budget of the exoplanetary spectrum to be retrieved. Given the instrument specications as of date, we investigate the magnitudes of these photometric instabilities in the context of simulated observations of the exoplanet HD189733b secondary eclipse.