ИСТИНА

Despite the efforts of numerous experiments with different components of extensive air showers (EAS) in the last decades, the uncertainty in the all nuclei spectrum of primary cosmic rays is still high and the results on chemical composition of primary cosmic rays from different experiments contradict each other. In this study an overview of the SPHERE experiment based on detection of the Vavilov-Cherenkov radiation from EAS reflected from the snow surface and of various experiments based on the same method in the same energy region E>10^15 eV is given. In particular, experimental results, methods of analysis of collected data along with subsequent methods of spectrum and mass composition reconstruction, their advantages and weak points are discussed. The first results on the energy spectrum and mass composition reconstruction of the SPHERE experiment are given and discussed and the main sources of systematic uncertainties that can affect these results are evaluated. Finally prospects of the SPHERE experiment and this technique are given.