The most significant progress in x-ray astronomy in the past few years has been brought about by the advent of satellite observatories and by the great number of new radio and optical identifications of cosmic x-ray sources. Since the discovery, with rocket-borne instruments, of extrasolar sources of x radiation ten years ago, it has been clear to most experimenters that a very considerable advance in our knowledge could be obtained with satellite instrumentation. The launch on 12 December 1970 of the first small astronomy satellite, UHURU, entirely devoted to x-ray observations, was expected to lead to the detection of fainter sources with finer angular resolution and positional accuracy, thereby expanding our catalog of celestial x-ray emitters. What was unexpected was the qualitative change in our understanding of the nature of cosmic x-ray emitting objects that several new discoveries by UHURU have brought about.