SPI is a coded-mask telescope aboard INTEGRAL, with a 19-element Germanium solid-state detector camera and a massive anticoincidence shield of BGO scintillation detectors. Detectors are maintained at ~90K through Stirling coolers. The spectral resolution is fine enough to resolve astrophysical lines and allow spectroscopy in the regime of gamma-rays. The coded mask provides imaging at moderate resolution.
Science objectives are nucleosynthesis, relativistic-particle accelerators, and strong-field signatures in compact stars; this is studied through nuclear lines and spectral features in accreting binaries, pulsars, or solar flares, but also through energetic continuum radiation in the 20 keV - 10 MeV range from the variety of cosmic sources, including AGN and gamma-ray bursts.

SPI is a collaborative international project, with IRAP(CESR) Toulouse and MPE as PI-Institutes (CESR Co-PI Jean-Pierre Roques, MPE Co-PI Roland Diehl). CESR provided the Ge Camera, and coordinated the overall instrument assembly with CNES as main industry contractor. The MPE provided the anticoincidence system ('ACS') of SPI, the GACE institute at the University of Valencia provided the coded mask, and CEA Saclay the electronics systems.  Instrument operations are managed by the CESR group (J.P. Roques), the ACS performance is optimized by MPE (A.von Kienlin). Data processing and initial analysis is centralized for INTEGRAL at the ISDC, with secondary processing pipelines and databases at CESR and MPE.

Acknowledgement (for all publications using SPI data): "The SPI project has been completed under the responsibility and leadership of CNES/France.We are grateful to ASI, CEA, CNES, DLR, ESA, INTA, NASA and OSTC for support." [plus for german-led papers: " The SPI anticoincidence system is supported by the German government through DLR grant 50.0G.9503.0."]