The results from measuring several parameters of the Antarctic atmosphere’s lower layers over the period 2004 through 2014 (Russian Antarctic expeditions 49 through 59) are presented. Such atmospheric parameters as the altitude dependence of the velocity and direction of the ground wind, the level of background radiation, and the concentrations of ozone and singlet oxygen are studied. Devices are installed on board the vessel Akademik Fedorov and at Antarctic ground stations. Tethered balloons are also used.

Представлен новый метод оценки типа частиц первичных космических лучей в области энергий 10–1000 ПэВ для индивидуальных событий, зарегистрированных установкой СФЕРА-2. Метод основан на сравнении образов зарегистрированных событий с моделированными событиями в предположении различных типов первичной частицы с учетом погрешностей измерения. Исследование направлено на поиск предела чувствительности в определении химического состава первичных космических лучей сверхвысоких энергий при использовании метода регистрации отраженного черенковского света широких атмосферных ливней.

A new method for assessing the type of particles of primary cosmic rays in the energy range of 10–1000 PeV for individual events recorded by the SPHERE-2 facility is presented. The method is based on comparing images of recorded events and simulated events, while assuming various types of primary particles with allowance for measuring errors. The aim of the study is to find the limits of sensitivity in determining of the chemical composition of ultrahigh-energy primary cosmic rays using the detection of reflected Cherenkov light generated by extensive air showers (EASes).

First preliminary results of the balloon-borne experiment SPHERE-2 on the all-nuclei primary cosmic rays (PCR) spectrum and primary composition are presented. The primary spectrum in the energy range 1016–5 · 1017 eV was reconstructed using characteristics of Vavilov-Cherenkov radiation of extensive air showers (EAS), reflected from a snow surface. Several sources of systematic uncertainties of the spectrum were analysed. A method for separation of the primary nuclei' groups based on the lateral distribution function' (LDF) steepness parameter is presented. Preliminary estimate of the mean light nuclei' fraction f30-150 at energies 3 · 1016–1.5 · 1017 eV was performed and yielded f30-150 = (21±11) %.

The devices for measuring the radiation level and wind speed in the balloon version are described. The results of measurements in Antarctica and during the Academician Fedorov research ship travel are presented.

Here is presented the current state of the SPHERE-2 balloon-borne experiment. The detector is elevated up to 1 km above the snow surface and registers the reflected Vavilov-Cherenkov radiation from extensive air showers. This method has good sensitivity to the mass-composition of the primary cosmic rays due to its high resolution near the shower axis. The detector consists of a 1500 mm spherical mirror with a 109 PMT cluster in its focus. The electronics record a signal pulse profile in each PMT. In the last 2 years the detector was upgraded: time resolution of pulse registration was enhanced up to 12.5 ns, channel sensitivity was increased by a factor of 3, a new LED-based relative PMT calibration method was introduced, and new hardware and etc. was installed.

The SPHERE-2 detector was lifted above the snow-covered surface of Lake Baikal by a captive balloon several times in 2010. The Vavilov-Cherenkov radiation of extensive air showers was measured. Preliminary results from processing the data of the SPHERE-2 experiment at various altitudes of observation are presented.

В начале 2010 г. проведено несколько подъемов установки СФЕРА-2 с помощью привязного аэростата над заснеженной поверхностью озера Байкал. Были проведены измерения черенковского света широких атмосферных ливней (ШАЛ). Приведены предварительные результаты обработки данных эксперимента СФЕРА-2 на различных высотах наблюдения.

The expedition carried out; in March, 2008 to Lake Baikal became an important stage in the development of the SPHERE experiment. During the expedition the SPHERE-2 installation was hoisted, for the first time, on a tethered balloon, APA, to a height of 700 to over the lake surface covered with ice and snow. A series of test measurements were made. Preliminary results of the data processing are presented. The next plan of the SPHERE experiment is to begin a set of statistics for constructing the CR spectrum in the energy range 10(16) - 10(18) eV.

The modern status of the SPHERE experiment and the method to determine the primary energy and the kind of the primary nuclear particles is presented. The SPHERE experiment is based on A.E.Chudakov's suggestion to use a new method for investigating the ultra high energy primary cosmic ray energy spectrum [1]. A small device lifted above the snow surface of the Earth detects the Cherenkov light of extensive air showers reflected from the surface. The relatively simple detector SPHERE-2 (spherical mirror 1.5m diameter and retina of 100 pixels) is presented. The next plan of the SPHERE experiment is to start measurements of the cosmic ray spectrum in the energy range 10(16) - 10(18) eV above the snow surface of Lake Baikal.

The results of simulation showing the possibility of mass analysis of primary cosmic-ray particles in the energy range 1016–1018 eV with the use of the SPHERE-2 balloon system are reported. The system is lifted by a tethered balloon at an altitude of 1 km. It has almost continuous sensitivity at an area of about 1 km2 that is viewed by 109 photoelectron multipliers. This property makes it possible to analyze in detail the spatial distribution of Cherenkov light in extensive air showers both in the immediate vicinity of the EAS core and at large distances from it.

The experiment SPHERE is based on a A.E. Chudakov's suggestion to use a new method for investigations of the energy spectrum of ultrahigh-energy primary cosmic rays. A small device lifted up off a snowed surface of the Earth detects Cherenkov light of an extensive air shower that is reflected from the surface. A contemporary status of the experiment SPHERE, a description of the method, the first measurements of the background night starlight in the region of the Russian Antarctic station Novolazarevskaya are presented. A relatively simple detector SPHERE-2 including a spherical mirror of the diameter 1.5m and a 100-pixel retina is developed for Antarctic balloon-borne measurements of the cosmic ray spectrum. A long-time winter flight makes it possible to measure the spectrum above 1020eV. A comparison with satellite and ISS projects of the nearest future shows that efficiency of this detector is sufficiently high.

The preparations to the measurements of UHE CR on the base of Russian Antarctic Station Novolazarevskaja using detectors SPHERE-1 and SPHERE-2 are fulfilled now. In this connection Monte-Carlo simulation was applied to estimate the accuracy of reconstruction of the EAS arrival direction and the Cherenkov light lateral distribution measured using the SPHERE-1 and SPHERE-2 balloon borne detectors at a height of 1 km by EAS Cherenkov light reflected from the Earth snowed surface.

The preparations to the measurements of UHE CR on the base of Russian Antarctic Station Novolazarevskaja using detectors SPHERE-1 and SPHERE-2 are fulfilled now. In this connection Monte-Carlo simulation was applied to estimate the accuracy of reconstruction of the EAS arrival direction and the Cherenkov light lateral distribution measured using the SPHERE-1 and SPHERE-2 balloon borne detectors at a height of 1 km by EAS Cherenkov light reflected from the Earth snowed surface.