The solar pointed satellite SAC-B has been designed and will be built in Argentina. It will carry on-board an spectrometer aimed to the detection of hard X-ray produced in solar flares and other short and rapidly varying cosmic phenomena. It will carry also a second instrument observing at the anti-solar direction the soft X-ray cosmic background. The Hard X-Ray Spectrometer (HXRS) built at IAFE is a NAI (Tl) scintillator, that works normally within the 20 to 320 keV energy range, extensible by command up to about 600 keV. The HXRS will observe X-ray spectra with a good energy resolution and excellent time resolution (down to few milliseconds for the most intense events) which provides its capability to study in detail the impulsive phase of solar flares and of those short and intense cosmic γ ray emissions known as γ Ray Bursts. The second instrument, designed and to be built by the Penn State University, USa, is called CUBIC (Cosmic Unresolved X-Ray Background Instrument with CCDs) and is aimed to measure the isotropic background intensities and spectral shape and lines with high energy resolution in the range 0.1 to 10 keV.Asociación Argentina de Astronomía