Properties and performance of the prototype instrument for the Pierre Auger observatory

Construction oft he first stage of the Pierre Auger Observatory has begun. The aim of the Observatory is to collect unprecedented information about cosmic rays above 1018 eV: The first phase ofth e project, the construction and operation ofa prototype system, known as the engineering array, has now been completed. It has allowed all of the sub-systems that will be used in the full instrument to be tested under field conditions. In this paper, the properties and performance of these sub-systems are described and their success illustrated with descriptions ofso me of the events recorded thus far.