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L. Scarsi (Istituto Fisica Cosmica e Informatica)
The X-ray Astronomy satellite SAX was launched on April 30, 1996 from Cape Canaveral into a circular orbit of 600 Km height, with an inclination of 3.9 degrees to the Equator. After launch it was renamed BeppoSAX adding the nickname "Beppo" in honor of Giuseppe "Beppo" Occhialini. BeppoSAX is a major program of the Italian Space Agency, with participation of the Netherlands Agency for Aerospace Programs. The scientific payload comprises a package of co-aligned (Z axis) Narrow Field of View (NFI) instruments allowing broad-band spectroscopy (E /DE ~ 12) in the energy range (0.1-10 keV) with imaging resolution of 1\arcmin and continuum / line spectroscopy for 3-200 keV (E / DE ~ 5-20). The payload is complemented by 2 Wide Field Cameras covering large regions of the sky (20 x 20 degrees) in diametrically opposed directions (along the Y axis) perpendicular to NFI axis; the WFC have angular resolution better than 3\arcmin, with an energy range 2 - 30 keV. Finally, there is Gamma Ray Burst Monitor (GRBM), with sensitivity to fluxes > 10^-6 erg /cm^2 in the range 60-600 keV with temporal resolution of about 1 ms. During 2.5 years of operation, BeppoSAX has produced new and valuable results from the observation of both galactic and extragalactic sources, showing a complex temporal variability as a function of energy over the large (more than three decades) band covered. A spectacular breakthrough in the identification of the GRB sources has characterized the BeppoSAX mission. By exploiting, to the fullest the capacity of the Scientific payload and operation, the BeppoSAX team in charge of the GRBM has been able to pinpoint the source position by observing the X-ray afterglow and, by providing useful positional information to ground and space based Observatories operating in the radio, IR and optical bands, to allow fundamental progress in the understanding of the phenomenon. Systematic observations have taken place since January 1997; a comprehensive account of the results to date will be presented.