Ultra-high-energy cosmic rays: the experimental situation

The methods of detection of high-energy cosmic rays are briefly described a nd it is shown that results on the energy spectrum and arrival direction di stribution obtained above 4x10(19)eV confound theoretical expectation. Ther e is an urgent need for better statistics as only about 12 events above 10( 20) eV have been detected and the limit to the energy which cosmic rays can reach is not known. The new, funded, instruments, the Pierre Auger Observa tory and the Hi-Res fluorescence detector, are described and the plans for an ambitious satellite observatory (Airwatch/OWL) are outlined. (C) 2000 El sevier Science B.V. All rights reserved.