A Three-Thousand-Square-Kilometre Cosmic-Ray Surface Array: Aperture, Station Count and Event Rates Computed from the Flux

A ground array for ultra-high-energy cosmic rays is designed from the flux it must harvest: 1,540 water-Cherenkov stations on a 1.5 km triangular grid cover 3,000 square kilometres and present a geometric aperture of 8,482 square kilometres steradians for showers within 60 degrees of zenith. At adopted integral fluxes the array records about 170 events per year above 10 EeV and 55,983 per year above 1 EeV at partial efficiency. The stations are autonomous and solar-powered; the whole array totals 2,713 tonnes and averages 78 kW, almost none of it at any central site. All figures are computed from the stated flux and geometry model; the design is simulated, not measured.