In this brief review, I propose to give an account of the main facts about the cosmic radiation as they are at present known to us, and of the outstanding problems which await solution. The intention is to provide a suitable background against which to discuss the advantages to be gained by experiments with artificial satellites. I shall address myself particularly to those who are not specialists in the subject. During the past ten years, two aspects of the study of cosmic radiation have received particular attention: 1. The cosmic radiation provides us with a source of particles of much greater energy than any which we shall be able to generate in the next one or two decades. The great acclerators under construction will give us beams of protons with energies up to 25 GeV. It is possible that machines of similar design, employing the strong-focusing principle, will be constructed for energies up to 50 GeV. Such a machine has been designed, for example, by Russian scientists. But the construction of even larger machines would encounter great technical difficulties. Further, when a high-energy proton collides with one at rest, the energy made available in the C -system of the interaction, E a , increases only slowly with the speed of the primary particle, E p ; E a ~ E 1/2 p ; and it is this quantity E a which determines the amount of energy which can appear in the form of the rest-mass of new particles created in the collision. In this situation, it is not clear that the advantages to be gained would justify the great expense of even larger machines based on present methods.