Abstract
In the past few months x-ray astronomy has entered its third era, with the flood of observations from the first of a new generation of large satellites, HEAO-A. The first phase, of rocket flights, ended with the immensely successful satellite UHURU launched in 1970 and since then a succession of small satellites - principally the American SAS-3, the Dutch ANS and the British ARIEL V - have maintained the steady accumulation of observations which are possible with small-aperture instruments.