Telescope Array; Status and Prospects

The Telescope Array (TA) is the air shower experiment designed for observing extremely high energy cosmic rays. It consists of an array of scintillation counters covering the ground area of 760 km2 and 3 sets of air fluorescence telescopes placed in the perimeter of the array. The TA aims at making a decisive measurement of the cosmic ray spectrum in the GZK cutoff region, and pinning down the nature of cosmic rays exceeding 10^20 eV, which have been the subject of extensive studies by AGASA, HiRes and other air shower experiments. The TA is being constructed in Utah, USA, and the commissioning is expected in the spring of 2007. An extension of hybrid measurement is planned down to 1017.5 eV in order to elucidate the galactic to extra-galactic transition of cosmic ray sources (TALE proposal)