The SPI Spectrometer for the integral mission

SPI (Spectrometer for INTEGRAL) is a high spectral resolution gamma-ray tel escope to be flown on board the ESA mission INTEGRAL. It consists of an arr ay of 19 closely packed Germanium detectors surrounded by an active anticoi ncidence shield of EGO. The imaging capabilities of the instrument are obta ined with a tungsten coded aperture mask located 1.7 m from the Ge array. T he fully coded field-of-view is 16 degrees and the angular resolution appro ximate to 2 degrees. The energy range extends from 20 keV to 8 MeV with a t ypical energy resolution approximate to 2 keV at 1 MeV. The point-source na rrow-line sensitivity is estimated to be (3-7) x 10(-6) ph/cm(-2) s(-1) ove r most of the energy range of the instrument (E > 200 keV) for a 10(6) s ob serving time. With these expected performances a major step forward can be expected in fine gamma-ray spectroscopy of astrophysical objects.