Аннотация:Relatively simple detector SPHERE (spherical mirror $\sim 1.5 m^2$ and retina of 100 pixels) is presented for the Antarctic balloon-borne measurements of the CR spectrum. Long time winter flight make it possible to measure the spectrum above $10^{20}$ eV. Comparison with satellite and ISS projects of the nearest future show that the efficiency of this detector is sufficiently high. The energy threshold is less ($\sim 10^{18}$ eV). The accuracy of the energy definition is high
as two methods are together -- the measurement of the EAS fluorescence track in the atmosphere and the measurement of the full flux of the EAS Cherenkov light.
