The researches at GEPI have as primary goal to understand the formation and evolution of stars, our own Galaxy and of the galaxies, in general, that constitute the baryonic matter of the Universe. This requires an increasing competence in many disciplines, ranging fron chemistry to physics, intrumentation and engineering, from project management to financial management in an international framework.
The motto, that summarises the activities of GEPI is « from instrumental conception to the exploitation of data and their modelling ». The field of activity from stellar physics to galactic physics assembles some unique competences and know-how from high resolution spectroscopy to 3D spectroscopy, from detailed chemical analysis of stars to multi-wavelength analysis of galaxies. These activities require cutting-edge mastering of physical phenomena and their understanding via observations. This also implyes the use of a vast choice of instruments. GEPI is at the heart of several priority projects in the field. Its know-how and scientific quality are internationally recognized and the European agencies (ESA, ESO) give to GEPI important responsabilities in many projects. Working upon its experience on the Hipparcos mission, GEPI is the French laboratory providing the largest contribution to the Gaia satellite, cornerstone mission of ESA, to be launched in 2013. The European laboratories are fully are fully responsible for the developpment and deployment of the data reduction software of the mission and GEPI dedicates to this about 10 FTEs (Full Time Equivalent) per year, with important responsabilities within the consortium. The succes of the VLT/FLAMES instrument, with the Giraffe spectrograph, built by a GEPI team, and that, not of lesser importance of the X-shooter instrument, that saw its first light in 2009, testify the major implication of GEPI in astronomical instrumentation. Furthermore GEPI is the French laboratory that is most engaged in the E-ELT project (European Extremely Large Telescope, with a major participation in the phase A study of two multi-obejct spectrographs and on adaptive optics system). The E-ELT constitutes the top priority of European astronomy (ASTRONET report). GEPI is also strongly engaged in low-frequency radioastronomy and has important responsabilities in the Square Kilometer Array (SKA) and its precursors (LOFAR, MeerKAT, ASKAP).
The GEPI is a tripartite Mixed Research Unit: it is a Department of Paris Observatory, a CNRS laboratory (UMR 8111) and a laboratory associated with the University Paris 7. It comprises four teams: Physics of Galaxies and Cosmology, Stellar and Galactic Physics, and the Instrumental Pole.