The SAX (Satellite per Astronomia X) mission is a major joint program
of the Italian Space Agency (ASI) and the Netherlands Agency for Space Programs
(NIVR). In the framework of past and future X-raymissions the SAX satellite, launched
in April 1996, stands out for its very wide spectral coverage from 0.1 to 200 keV, with
well-balanced performances of the low-energy and high-energy instrumentation. The
sensitivity of the scientific payload will allow the exploitation of the full band of SAX
also for weak sources (1/20 of 3C273), opening new perspectives in the study of spectral
shape and variability of several classes of objects. In this paper we describe the main
aspects of the mission, the instruments, the scientific objectives and operations