ИСТИНА

We consider spatial and temporal characteristics of optical Vavilov-Cherenkov radiation (“Cherenkov light”, CL) reflected from the snow surface of Lake Baikal, as registered by the SPHERE-2 detector. We perform detailed full direct Monte Carlo (MC) simulations of EAS development and present a new version of a dedicated highly modular code intended for detector response simulations with account for realistic instrumental thresholds in every measurement channel, as well as noise. Detector response properties are illustrated by example of several model EAS events. The instrumental acceptance of the SPHERE-2 detector was calculated for a range of observation conditions. We introduce and discuss the concept of “composite model quantities”, calculated for detector responses averaged over photoelectron count fluctuations, but retaining EAS development fluctuations. The distortions of EAS CL lateral distribution function (LDF) introduced by the SPHERE-2 telescope are understood by comparing composite model LDF with the corresponding function as would be recorded by an ideal detector situated at the ground surface. Finally, we compare the reflected CL method with other experimental techniques and briefly discuss its prospects.