1. ASTEROSEISMOLOGY and SEARCH for EXOPLANETS Vienna - September 18 th 2001 Optical performance characterization Point Spread Function (PSF) : Telescope + Dioptric Objectif Sensitivity of the PSF with temperature (in 12 points of the field) Baffle performance characterization Modelisation of the straylight attenuation achieved with technical manufacturing hypothesis (coating diffusion, diffraction and quality of the chicanes against grazing incidence reflections, contamination) Caracterisation of this hypothesis after manufacture No possible measurement of the attenuation factor (10 -13 ) ACHIEVABLE CHARACTERIZATIONS ON THE INSTRUMENT

2. ASTEROSEISMOLOGY and SEARCH for EXOPLANETS Vienna - September 18 th 2001 Camera performance characterization To adjust interface between Objective and Focal Plane and to obtain the good PSF : Two optical system simulators - star simulator with the best representativity of the spectral response - colimator to simulate performances of telescope Caracterisation of the PSF sensitivity with temperature CCD Calibration : dark signal, uniformity, spectral quantum efficiency... Electronic performance characterization Noise value (rms and frequency determinist) Offset and gain Electronic performances (stability) are not compliant with the need of the mission : Corrections are necessary  Gain and offset sensitivity with temperature ACHIEVABLE CHARACTERISATIONS ON THE INSTRUMENT

3. ASTEROSEISMOLOGY and SEARCH for EXOPLANETS Vienna - September 18 th 2001 Technical difficulties to measure performances on the integrated instrument Attenuation of light for the baffle Quality and stability with the temperature of the PSF when the instrument is complitely integrated (in vacuum, at -40°C and class 100) Cost and delay for the instrument tests The modelisation allows : To assemble the performances of different sub-systems : Telescope + Dioptric Objectif Camera Electronic Scientific processing (with calibration data) To model the variation of performances with :  the variation of temperature along the orbit  the fluctuation of the pointing system To validate the expected gain with the ground correction Why a need of modelisation ?