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Abstract. Three calibration campaigns of the spectrometer SPI have been performed before launch in order to determine the instrument characteristics, such as the effective detection area, the spectral resolution and the angular resolution. Absolute determination of the effective area has been obtained from simulations and measurements. At 1 MeV, the effective area is 65 cm 2 for a point source on the optical axis, the spectral resolution ∼2.3 keV. The angular resolution is better than 2.5• and the source separation capability about 1• . Some temperature dependant parameters will require permanent in-flight calibration.