Search

Work is currently under way in the Tunka Valley, 50 km from Lake Baikal, to create the TAIGA gamma observatory for studying gamma radiation and cosmic ray fluxes in the 1013–1018 eV range of energies. To detect gamma rays with energies above tens of TeV, a hybrid method of detecting showers is implemented. It is based on data obtained by the TAIGA Imaging Atmospheric Cherenkov Telescope (IACT) and the wide-angle TAIGA-HiSCORE array. The preliminary results from processing the telescope’s data for the low-energy region (>2–3 TeV) are presented. Joint events with energy more than 50 TeV are analyzed and compared to Monte Carlo calculations.

The TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma-ray Astronomy) experiment aims at observing gamma-rays in the energy range from 1 TeV to several 100 TeV. The operation of the observatory is based on a new hybrid approach that combines imaging air Cherenkov telescopes (IACTs) and wide-angle Cherenkov detectors (TAIGA-HiSCORE) for measuring times of extensive air shower (EAS) light front arrival. Monte Carlo simulations are compared to real data to determine the performance of the detector setup. Dedicated software and algorithms are described, model parameters are given, and an overview of the current status of model-based performance studies is presented.

The concept of a multi-functional astronomical complex as applied to robotic astronomy networks and systems is formulated. The practical realization of this concept in the MASTER global network of robotic telescopes of Moscow State University is described. The dynamically integrated MASTER database, which transforms a network of robotic telescopes into a robotic network, is described. Real, multi-channel astronomical observations obtained on the MASTER global network are used to show the effective application of this concept. The MASTER global network is continuously participating in multi-wavelength and multi-channel observations aimed at studying astrophysical sources located in extreme conditions, including the sources of gravitational waves registered by the LIGO/VIRGO detectors, of high-energy neutrinos detected by IceCube and ANTARES, and of fast radio bursts (FRBs) and gamma-ray bursts (GRBs). The MASTER network provided the most extensive survey of the first error field for the LIGO gravitational-wave outburst GW 150914 (5000 square degrees) and carried out the first independent localization of the gravitational-wave event GW170817. TheMASTER network has also discovered more than 1600 optical transients with various physical natures. Data obtained with the MASTER network have been used to provide pointing information to major ground-based and space-based telescopes.

The physical motivations and performance of the TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) project are presented. The TAIGA observatory addresses ground-based gamma-ray astronomy at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV and astroparticle physics. The pilot TAIGA complex locates in the Tunka valley, ~50 km West from the southern tip of the lake Baikal. It includes integrating air Cherenkov TAIGA-HiSCORE array with 120 wide-angle optical stations distributed over on area 1 square kilometer about and three the 4-m class Imaging Atmospheric Cherenkov Telescopes of the TAIGA-IACT array. The latter array has a shape of triangle with side lengths of about 300m, 400m and 500m. The expected integral sensitivity of the 1 km2 TAIGA detector will be about 2,5 × 10-13 TeV cm-2 sec-1 for detection of E ≥ 100 TeV gamma-rays in 300 hours of source observations. The combination of the wide angle Cherenkov array and IACTs could offer a cost effective-way to build a really large (up to 10 km2) array for very high energy gamma-ray astronomy. The reconstruction of a given EAS energy, incoming direction and the core position, based on the TAIGA-HiSCORE data, allows one to increase the distance between the relatively expensive IACTs up to 600-800 m. These, together with the surface and underground electron/Muon detectors will be used for selection of gamma-ray induced EAS. Present status of the project, together with the current array description and the first experimental results and plans for the future will be reported.

A new knee-like approximation of the lateral distribution function (LDF) of EAS Cherenkov light in the 30–3000 TeV energy range was proposed and tested with simulated showers in our earlier studies. This approximation fits the LDFs of individual showers accurately for all types of primary particles gamma-rays, protons, and nuclei) and is suitable for reconstructing the shower core, determining the energy, and separating gamma-induced showers from hadron-induced ones. In the present study, the knee-like fitting function is used to determine the parameters of real showers detected by TAIGA-HiSCORE. It is demonstrated that this approximation characterizes properly all types of individual LDFs of experimental events in the 300–1000 TeV range. The accuracy of fit is governed by fluctuations intrinsic to the process of measurement of the Cherenkov photon density. The probability density function of these fluctuations was reconstructed and introduced into simulations. Certain useful methodical applications of the knee-like approximation are con-sidered, and the possibility of shower sorting into nuclei groups is examined. The extensive statistical coverage and detailed LDF measurement data of HiSCORE have provided the first opportunity to examine in depth the LDF of Cherenkov radiation in the 300–1000 TeV range.

Over the past few years, the TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma-ray Astronomy) observatory has been being deployed in the Tunka Valley, Republic of Buryatia. It is designed for studying gamma rays of energy above 30 TeV and performing searches for sources of galactic cosmic rays with energies in the vicinity of 1 PeV, which is an energy region around the classic knee in the cosmic-ray energy spectrum. The first phase of the observatory will be situated at a distance of about 50 km from Lake Baikal at the site of the Tunka-133 array. The TAIGA gamma observatory will include a network of 500 wide-angle (0.6 sr) Cherenkov detectors (TAIGA-HiSCORE array) and up to 16 atmospheric Cherenkov telescopes (ACT) designed for analyzing the EAS images (imaging atmospheric Cherenkov telescopes, or IACT) and positioned within an area of 5 km2. The observatory will also include muon detectors of total area 2000 m2 distributed over an area of 1 km2. Within the next three years, it is planned to enhance the area of the TAIGA-HiSCORE array by a factor of four—from 0.25 km2 to 1 km2; to supplement the existing IACT with two new ones; and to deploy new muon detectors with a total coverage of 200 m2. The structure of the new observatory is described along with the data analysis techniques used. The most interesting physical results are presented, and the research program for the future is discussed.

The article presents the relevance and advantages of the new gamma observatory TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy), which is being constructed in the Tunka Valley 50 km from Lake Baikal. Various detectors of the six TAIGA gamma observatory arrays register the Cherenkov and radio radiation, as well as the electron and muon components of EAS. The primary objective of the TAIGA gamma observatory is to study the high-energy part of the gamma-ray spectrum, in particular, in order to search for Galactic PeVatrons. The energy, direction, and position of the EAS axis are reconstructed in the observatory based on the data of the wide-angle Cherenkov detectors of the TAIGA-HiSCORE experiment. Taking into account this information, the gamma quanta are distinguished from the hadron background using the data obtained by the muon detectors and telescopes that register the EAS image in the Cherenkov light. In this hybrid mode of operation, the atmospheric Cherenkov telescopes can operate in the mono-mode, and the distance between them can be increased to 800–1000 m, which makes it possible to construct an array with an area of 5 km2 and more at relatively low cost and in a short time. By 2019, the first stage of the gamma observatory with an area of 1 km2 will be constructed; its expected integral sensitivity for detecting the gamma radiation with an energy of 100 TeV at observation of the source for 300 hours will be approximately $$2 \times 5$$ 10–13 TeV cm–2s–1.

The TAIGA experiment in the Tunka valley near Lake Baikal is planning an extension with new TAIGA-Muon scintillation detector stations. The main purpose of TAIGA is gamma-ray astronomy in the TeV to PeV energy range and cosmic ray physics. The purpose of the Taiga-Muon detectors is to measure the muon component of air showers for improving cosmic ray composition measurements as well as gamma–hadron separation above 100 TeV. Monte Carlo simulations of the experiment are done with the software packages CORSIKA and GEANT4. Extensive air showers of primary particles in the energy range 100–3000 TeV are created with CORSIKA. The trigger efficiency is calculated and used for optimization. The suppression factor of hadronic showers versus electromagnetic showers is studied, leading to an optimum depth of soil absorber (2 m), at the lowest energy range. Data on the identification efficiency for primary gamma-quanta and proton events are presented as well as the suppression factor.

We present the earliest astronomical observation of a high energy neutrino error box in which its variability was discovered after high-energy neutrinos detection. The one robotic telescope of the MASTER global international network (Lipunov et al. 2010) automatically imaged the error box of the very high-energy neutrino event IceCube-170922A. Observations were carried out in minute after the IceCube-170922A neutrino event was detected by the IceCube observatory at the South Pole. MASTER found the blazar TXS 0506+056 to be in the off-state after one minute and then switched to the on-state no later than two hours after the event. The effect is observed at a 50-sigma significance level. Also we present own unique 16-years light curve of blazar TXS 0506+056 (518 data set)., 17 pages, 3 figures, 1 Table accepted to The Astrophysical Journal Letters

The Tunka-Grande scintillation array is described. The first results from its operation are presented. The prospects for studying primary cosmic rays in the energy range of 1016 to 1018 eV during simultaneous registration of the Cherenkov and charged particle components along with radio emissions from extensive air showers are discussed.

The Tunka-Grande and TAIGA-Muon arrays are the part of a single experimental complex, which also includes the Tunka-133 and TAIGA-HiSCORE (High Sensitivity COsmic Rays and gamma Explorer) wide-angle Cherenkov arrays, TAIGA-IACT array (Imaging Atmospheric Cherenkov Telescope) and Tunka-Rex radio antennas array (Tunka Radio Extension). This complex is located in the Tunka Valley (Buryatia Republic, Russia), 50 km from Lake Baikal. It is aimed at investigating the energy spectrum and mass composition of charged cosmic rays in the energy range 100 TeV - 1000 PeV, searching for diffuse gamma rays above 100 TeV and studying local sources of gamma rays with energies above 30 TeV. This report outlines 3 key points. The first is a description of the Tunka-Grande and TAIGA-Muon scintillation arrays. The second part presents preliminary results of the search for diffuse gamma rays with energies above 50 PeV according to the Tunka-Grande data. The third part is devoted to the prospects of the search for diffuse gamma rays with energies above 100 TeV using the TAIGA-Muon array.

TAIGA array addresses gamma-ray astronomy at energies from a few TeV to several PeV as well as cosmic ray physics from 100 TeV to several EeV. A 1 km2 TAIGA setup will consist of 120 wide-angle detectors of the Cherenkov timing array TAIGA-HiSCORE and three imaging air Cherenkov telescopes with the field of view diameter of 9.6°. In this paper, first experimental results of the first operation stage are presented: signal detection from two gamma-ray sources, the Crab Nebula and Markarian 421, by the first IACT in stand-alone mode. The detected signal is shown to be in agreement with the Monte Carlo expectation. In future, gamma-ray signal will be detected by a larger number of TAIGA telescopes as well as the TAIGA-HiSCORE array, that is, in combined operation mode.

The Tunka Radio Extension (Tunka-Rex) is a digital antenna array for the detection of radio emission from cosmic-ray air showers in the frequency band of 30 to 80 MHz and for primary energies above 100 PeV. The standard analysis of Tunka-Rex includes events with zenith angle of up to 50$^\circ$. This cut is determined by the efficiency of the external trigger. However, due to the air-shower footprint increasing with zenith angle and due to the more efficient generation of radio emission (the magnetic field in the Tunka valley is almost vertical), there are a number of ultra-high-energy inclined events detected by Tunka-Rex. In this work we present a first analysis of a subset of inclined events detected by Tunka-Rex. We estimate the energies of the selected events and test the efficiency of Tunka-Rex antennas for detection of inclined air showers., ARENA2018 proceedings

The Tunka Radio Extension (Tunka-Rex) is a digital radio array operating in the frequency band of 30-80 MHz and detecting radio emission from air-showers produced by cosmic rays with energies above 100 PeV. The experiment is installed at the site of the TAIGA (Tunka Advanced Instrument for cosmic rays and Gamma Astronomy) observatory and performs joint measurements with the co-located particle and air-Cherenkov detectors in passive mode receiving a trigger from the latter. Tunka-Rex collects data since 2012, and during the last five years went through several upgrades. As a result the density of the antenna field was increased by three times since its commission. In this contribution we present the latest results of Tunka-Rex experiment, particularly an updated analysis and efficiency study, which have been applied to the measurement of the mean shower maximum as a function of energy for cosmic rays of energies up to EeV. The future plans are also discussed: investigations towards an energy spectrum of cosmic rays with Tunka-Rex and their mass composition using a combination of Tunka-Rex data with muon measurements by the particle detector Tunka-Grande., Comment: ARENA2018 proceedings

The combination of a wide angle timing Cherenkov array and Imaging Atmospheric Cherenkov Telescopes operated in mono mode offers a cost-effective way to construct a few square kilometers array for ultrahigh-energy gamma astronomy. The first stage of the TAIGA Observatory (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) is described here. It will comprise TAIGA-HiSCORE - 120 wide angle Cherenkov stations distributed over an area of 1.0 km2 and three IACTs (TAIGA-IACT).

The Tunka-HISCORE wide-angle Cherenkov array, one part of the planned TAIGA integrated gamma observatory intended for investigations in the field of high-energy (>30 TeV) gamma-ray astronomy and cosmic-ray physics, is deployed in the Tunka Valley (Buryat Republic). The first results from operating a prototype array composed of nine stations spread over an area of ∼0.1 square kilometers during the winter of 2013–2014 are presented. Data processing techniques are described, along with data on the accuracy of reconstructing the position of a shower’s axis, energy, and angle of arrival. The differential spectrum of all cosmic-ray particles in a shower in the energy range of 2 × 1014 to 2 × 1016 eV is presented and compared to the available data.

International audience; This paper presents the first investigation results of possible coincidences of optical transients in the MASTERglobal robotic telescope net database with the localization regions of VHE and UHE neutrino alert events fromANTARES and IceCube observatories. MASTER is the first robotic telescopic system in Russia, dedicated tooptical observation and registration of the most energetic and fastest explosive processes in the Universe. Thegoal is a deeper and more thorough study of space and time coincidences of the MASTER optical transientsand high energy neutrinos.

The very to ultra high energy gamma-ray regime up to several 100 TeV is the key to spectrally resolve the cutoff regime of the long-sought Pevatrons, the Galactic cosmic-ray PeV accelerators. One component of the TAIGA hybrid detector is the TAIGA-HiSCORE shower-front sampling timing array, which currently consists of 28 wide angle (0.6\,sr) air Cherenkov timing stations distributed on an area of 0.25 km$^{2}$, and which will be doubled in area by fall 2017. We report on the status and first results of the HiSCORE timing array after the first 2 operation seasons, including calibration studies on timing and pointing, cross calibration with data from the first TAIGA-IACT, observations with the timing array of a LIDAR operating on the ISS, a measurement of the Cosmic Ray spectrum, and a systematic search for high energy gamma-rays from Galactic sources such as the Crab.

Tunka-Rex (Tunka Radio Extension) is an antenna array for cosmic-ray detection located in Siberia. Previous studies of cosmic rays with Tunka-Rex have shown high precision in determining the energy of the primary particle and the possibility to reconstruct the depth of the shower maximum. The next step is the reconstruction of the mass composition and the energy spectrum of cosmic rays. One of the main problems appearing within this task is to estimate the detection efficiency of the instrument, and the exposure of the observations. The detection efficiency depends on properties of the primary cosmic rays, such as energy and arrival direction, as well as on many parameters of the instrument: density of the array, efficiency of the receiving antennas, signal-detection threshold, data-acquisition acceptance, and trigger properties. More than that, the configuration of detector changes with time. During the measurements some parts of the detector can provide corrupted data or sometimes do not operate. All these features should be taken into account for an estimation of the detection efficiency. For each energy and arrival direction we estimate the detection probability and effective area of the instrument. To estimate the detection probability of a shower we use a simple Monte Carlo model, which predicts the size of the footprint of the radio emission as function of the primary energy and arrival direction (taking into account the geometry of Earth's magnetic field). Combining these approaches we calculate the event statistics and exposure for each run. This is the first accurate study of the exposure for irregular large-scale radio arrays taking into account most important features of detection, which will be used for the measurement of primary cosmic-ray spectra with Tunka-Rex.

A central question of Astroparticle Physics, the origin of cosmic rays, still remains unsolved. HiSCORE (Hundred*i Square-km Cosmic ORigin Explorer) is a concept for a large-area wide-angle non-imaging air shower detector, addressing this question by searching for cosmic ray pevatrons in the energy range from 10TeV to few PeV and cosmic rays in the energy range above 100TeV. In the framework of the Tunka-HiSCORE project, first prototypes have been deployed on the site of the Tunka-133 experiment, where we plan to install an engineering array covering an area of the order of 1km2. On the same site, also imaging and particle detectors are planned, potentially allowing a future hybrid detector system. Here we present the HiSCORE detector principle, its potential for cosmic ray origin search and the status of ongoing activities in the framework of the Tunka-HiSCORE experiment.

We present the main results of the Extensive Air Shower Cherenkov array Tunka-25. They cover the energy spectrum from 8 · 1014 to 1017 eV and mass composition of primary cosmic rays in the energy range of 3·1015 − 3 · 1016 eV. A new lateral distribution function (LDF) of Air Shower Cherenkov light and a new method to analyze the maximum depth distribution of the shower have been developed. Both have been successfully applied in the data analysis of Tunka-25. We also discuss methods of time and amplitude calibration of the array, providing an accurate determination of the primary energy and the steepness of the LDF.

We present physical motivations and advantages of the new gamma-observatory TAIGA (Tunka Advanced Instrument for cosmic ray physics and gamma-ray astronomy). TAIGA will be located in the Tunka valley, 50 km to the west of Lake Baikal, at the same place as the integrating air Cherenkov detector for cosmic rays Tunka-133. The TAIGA array is a complex, hybrid detector for ground-based gamma-ray astronomy for energies from a few TeV to several PeV as well as for cosmic ray studies from 100 TeV to several EeV. The array will consist of a wide angle Cherenkov array – TAIGA-HiSCORE with 5km2 area, a net of 16 IACT telescopes (with FOV of about 9.72°×9.72°) as well as muon and other detectors. We present the current status of the array construction.

The operation of large underwater neutrino telescopes requires the precise knowledge of the water parameters governing light absorption and scattering, as well as a continuous monitoring of these parameters. For this purpose, a stationary underwater device, ASP-15, has been developed by the Baikal collaboration. We describe the basic assumptions and formulae behind ASP-15, the methods how absorption length, scattering length and phase functions are determined, the design of the device, and give some results obtained over many years of operation in conjuction with the Baikal telescope NT200.

The currently running NT200 and NT200+ Baikal neutrino telescopes and the prospects for development of the Baikal Neutrino Project are briefly descr⇊ed. Preliminary results of the search for neutrino events correlated with cosmological gamma-ray bursts at the NT200 are presented. The feasibility of developing a method for acoustic detection of ultrahigh-energy neutrinos in the Baikal Neutrino Project is discussed. The calculation results for the energy spectrum and zenith-angle distributions of atmospheric neutrinos in the energy range from 10 to 107 GeV obtained within various high-energy hadron-nucleus interaction models are presented.

In TAIGA Observatory (Tunka Advanced Instrument for cosmic ray physics and Gamma-ray Astronomy) we are commissioning the first Imaging Atmospheric Cherenkov Telescope (IACT). The telescope has an alt-azimuth mount and 17-bit shaft encoder for each axis, stepper motors are used for axis control. For the pointing calibration of the telescope a CCD-camera is installed on the dish of the telescope and its position allows to capture simultaneously both the Cherenkov camera with LEDs and the sky with observed source. Since October 2017, the telescope has been operating in tracking mode. In this work the TAIGAIACT telescope pointing calibration approach and first results of the tracking operations are described.

The history, current status, and prospects for the development of the Baikal Neutrino Project are considered. The main physical results obtained with the help of NT200 and NT200+ neutrino telescopes are presented.

We review the status of high-energy acoustic neutrino detection activities in Lake Baikal. The Baikal collaboration constructed a hydro-acoustic device which may be regarded as a prototype subunit for a future underwater acoustic neutrino telescope. The device is capable of common operation with the Baikal neutrino telescope NT200+, and is operating at a depth of about 150 m on the “NT200+ instrumentation string”. Our measurements show that the integral noise power in the frequency band 20–40 kHz can reach levels as low as about 1 mPa, i.e. one of the lowest noise levels measured at the currently considered acoustic neutrino sites. At the same time, short acoustic pulses with different amplitudes and shapes have been observed. Low sound absorption in Baikal freshwater and absence of strong acoustic noise sources do motivate further activities towards a large-scale acoustic neutrino detector in Lake Baikal.

An optical detector and an electronic system have been developed for studying the shape of Cherenkov light pulses from extensive air showers in the TUNKA experiment. Results of measurements on the described experimental setup are presented.

We review the status of the Baikal Neutrino Experiment. The Neutrino Telescope NT200 is operating in Lake Baikal since 1998 and has been upgraded to the 10 Mton detector NT200+ in 2005. We present selected results concerning astroparticle physics as well as results of environmental studies. We describe the strategy of creating a Gigaton (km3) scale neutrino detector at Lake Baikal. First steps of activities towards a km3 Baikal neutrino telescope, including the development of acoustic high energy neutrino detection method are discussed.

Physics letters / B 763, 179 - 185(2016). doi:10.1016/j.physletb.2016.10.031, The radio technique is a promising method for detection of cosmic-ray air showers of energies around View the MathML source100PeV and higher with an array of radio antennas. Since the amplitude of the radio signal can be measured absolutely and increases with the shower energy, radio measurements can be used to determine the air-shower energy on an absolute scale. We show that calibrated measurements of radio detectors operated in coincidence with host experiments measuring air showers based on other techniques can be used for comparing the energy scales of these host experiments. Using two approaches, first via direct amplitude measurements, and second via comparison of measurements with air shower simulations, we compare the energy scales of the air-shower experiments Tunka-133 and KASCADE-Grande, using their radio extensions, Tunka-Rex and LOPES, respectively. Due to the consistent amplitude calibration for Tunka-Rex and LOPES achieved by using the same reference source, this comparison reaches an accuracy of approximately 10%10% – limited by some shortcomings of LOPES, which was a prototype experiment for the digital radio technique for air showers. In particular we show that the energy scales of cosmic-ray measurements by the independently calibrated experiments KASCADE-Grande and Tunka-133 are consistent with each other on this level., Published by North-Holland Publ., Amsterdam

The 10 Mton scale Neutrino telescope NT 200 + is operating in Lake Baikal since April, 2005. It's main physics goal is the detection of high energy neutrino cascades in the 10 2 – 10 5 TeV energy range. The NT 200 + sensitivity to astrophysical diffuse neutrinos is four times that of it's predecessor NT200 the telescope that has been operating since 1998, yielding a variety of physics results. A km-scale (Gigaton Volume) Neutrino telescope in Lake Baikal is planned, the R&D phase has started in 2006. We give the basic layout of this Baikal km3-detector, which will be made of building blocks similar to NT 200 + .

The Baikal neutrino telescope NT200 takes data since 1998. In 2005, the deployment of three additional strings for common operation with NT200 was finished. We describe the physics program and the design of the new telescope named NT200+ and present selected physical results obtained with NT200. First results from NT200+ will be presented at the conference., Comment: 4 pages, 5 figures, Proceedings of 29th International Cosmic Ray Conference (ICRC) 2005, Pune, India

Spatial distribution of Cerenkov radiation of extensive air shower particles with energies 1013–1016 eV is simulated by the CORSIKA code for conditions and configuration of the Tunka-25 facility. Based on the calculated results, sets of approximating functions are constructed for different primary particles and zenith angles. A comparison of the calculated spatial distribution functions of Cerenkov light with the functions measured on the Tunka-25 facility demonstrates the feasibility of identification of the particle initiating the shower and determination of its energy in the vicinity of the bend point of the cosmic ray spectrum.

We review the present status of the Baikal neutrino experiment. The structure and parameters of the neutrino telescope NT-200, which was put into operation in April 1998, are described. Selected methodological results are presented. Physics results cover separating up-going muons from atmospheric neutrinos, searches for neutrino events from WIMP annihilation, searches for magnetic monopoles, and high-energy neutrinos.

Tunka-Rex is a radio detector for cosmic-ray air showers in Siberia, triggered by Tunka-133, a co-located air-Cherenkov detector. The main goal of Tunka-Rex is the cross-calibration of the two detectors by measuring the air-Cherenkov light and the radio signal emitted by the same air showers. This way we can explore the precision of the radio-detection technique, especially for the reconstruction of the primary energy and the depth of the shower maximum. The latter is sensitive to the mass of the primary cosmic-ray particles. In this paper we describe the detector setup and explain how electronics and antennas have been calibrated. The analysis of data of the first season proves the detection of cosmic-ray air showers and therefore, the functionality of the detector. We confirm the expected dependence of the detection threshold on the geomagnetic angle and the correlation between the energy of the primary cosmic-ray particle and the radio amplitude. Furthermore, we compare reconstructed amplitudes of radio pulses with predictions from CoREAS simulations, finding agreement within the uncertainties., Comment: Description and Calibration paper for Tunka-Rex

The TAIGA observatory addresses ground-based gamma-ray astronomy at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV . TAIGA will be located in the Tunka valley, ~ 50 km West from Lake Baikal. The different detectors of the TAIGA will be grouped in 6 arrays to measure Cherenkov and radio emission as well as electron and muon components of atmospheric showers. The combination of the wide angle Cherenkov detectors of the TAIGA-HiSCORE array and the 4-m Imaging Atmospheric Cherenkov Telescopes of the TAIGA-IACT array with their FoV of 10×10 degrees and underground muon detectors offers a very cost effective way to construct a 5 km2 array for gamma-ray astronomy.

A Cerenkov detector of extensive air showers developed for joint operation with the Baikal deep-water HT-200 neutrino telescope is described.

The status of the Baikal neutrino experiment is briefly reviewed and the results of the search for the natural flux of high-energy neutrinos are reported.

The Baikal neutrino telescope NT200 is in operation since April, 1998. We present physics results obtained with this detector during 1998–2002. Since April 2005, the upgraded 10-Mton scale telescope NT200+ is operating. For a km3-scale neutrino telescope in Lake Baikal, the R&D phase has started in 2006.

As a non-imaging wide-angle Cherenkov air shower detector array with an area of up to 100 km 2 , the HiSCORE (Hundred⁎i Square km Cosmic ORigin Explorer) detector concept allows measurements of gamma rays and cosmic rays in an energy range of 10 TeV up to 1 EeV. In the framework of the Tunka-HiSCORE project we have started measurements with a small prototype array, and planned to build an engineering array (1 km 2 ) on the site of the Tunka experiment in Siberia. The first results and the most important hardware components are presented here.

We report on the current state of the Baikal acoustic neutrino detection project. The new results of pulse simulation are presented. The Askarian approach was exploited to calculate the acoustic pulses produced by ultra-high-energy (UHE) particles. Preliminary results of the telescope effective volume estimation are presented. It is described how new Acoustic Sensor Modules are put into operation.

Since one and a half year, the underwater Cherenkov telescope NT-36 consisting of 36 photomultipliers attached to 3 strings is operated in lake Baikal. The large statistics of collected data allows for comparison with Monte Carlo predictions starting from the level of detector response up to more sophisticated dependences like the angular distribution of muon intensity.

We report the present status and perspectives of the feasibility study to detect cosmic neutrinos acoustically in the Lake Baikal. The results of background studies are presented. It was shown that most of the detected neutrino-like pulses come from the lake surface. This fact has been used in the project of an acoustic prototype detector that consists of compact Acoustic Sensor Modules with 4-channel antennas each, arranged above the Baikal Neutrino Telescope at shallow depths and “listening” the deep-water layers of the lake.

Addressing the mysteries of cosmic rays requires a comprehensive observational approach, including information on mass composition and spectrum (from CR nuclei) as well as directional information (gamma-rays or neutrinos). HiSCORE covers both approaches using indirect air-shower observations of cosmic rays from 100 TeV to 1 EeV and gamma-rays in the so far poorly covered energy range from 10 TeV to several PeV. Among other questions of astroparticle and particle physics, HiSCORE will allow cosmic ray composition and spectral measurements in the transition range between Galactic and Extragalactic origin. Searching for gamma-rays from the PeV-accelerators, the pevatrons, will consititute a crucial building-block for solving the question of the origin of Galactic cosmic rays. HiSCORE is an array of non-imaging light-collecting stations for Cherenkov light-front sampling. The lateral Cherenkov photon density and arrival-time distribution are measured, allowing the reconstruction of the direction, the energy, and the particle type (mainly shower depth) of the primary particle. A prototype detector station was developed and first air-shower measurements were performed in the Tunka valley (Siberia). The deployment of an engineering array of up to 1 square-km is planned on the Tunka cosmic ray experiment site in Siberia for 2012/2013.

The angular resolution of the Cerenkov detector of extensive air showers, developed for joint operation with the Baikal deep-water NT-200 neutrino telescope, was investigated. The angular resolution was shown to be within 1°.

A new array for studying ultra-high energy cosmic rays was inaugurated in 2009 in the Tunka Valley, about 50 km from Lake Baikal. Having an area of 1 km2, the new facility allows us to study cosmic rays with energies of 1015–1018 eV via the a unified method for registering Cherenkov radiation from extensive air showers (EASes) and is making a substantial contribution to understanding the origin of ultra-high energy cosmic rays. We describe the current state of the experiment, the new methodological approach, our initial results, and the plans for further development of the array.

Presented paper describes the basic principles and features of the implementation of a robotic network of optical telescopes MASTER, designed to study the prompt (simultaneous with gamma radiation) optical emission of gamma-ray bursts and to perform the sky survey to detect unknown objects and transient phenomena. With joint efforts of Sternberg astronomical institute, High altitude astronomical station of the Pulkovo observatory, Ural state university, Irkutsk state university, Blagoveshchensk pedagogical university, the robotic telescopes MASTER II near Kislovodsk, Yekaterinburg, Irkutsk and Blagoveshchensk were installed and tested. The network spread over the longitudes is greater than 6 hours. A further expansion of the network is considered., Comment: Accepted for publication in Experimental Astronomy, 18 pages, 11 figures

A project of the NT1000 deep-water neutrino telescope with an effective volume of ∼1 km3 is currently being developed by the BAIKAL collaboration. The telescope will be located in Lake Baikal in close vicinity of the NT200+ detector, which is currently in operation. The telescope will be composed of 12 clusters with 8 similar strings of optical modules in each (each string has two sections of the NT1000 optical modules). The section of the NT1000 optical modules has been developed using higher-efficiency photomultiplier tubes and state-of-the-art electronics. The field tests of the experimental string consisting of two sections with six optical modules in each have been performed. The results of these investigations are used in the project of the NT1000 neutrino telescope and in the hydrological study of Lake Baikal.

We describe the lake Baikal deep underwater detector “NT-200” and discuss its physics capabilities to investigate problems in the field of neutrino astrophysics, cosmic ray physics and particle physics.

A prototype string for the future km3-scale Baikal neutrino telescope has been deployed in April, 2008 and is fully integrated into the NT200+ telescope. All basic string elements - optical modules (with 12"/13" hemispherical photomultipliers), 200MHz FADC readout and calibration system - have been redesigned following experience with NT200+. First results of in-situ operation of this prototype string are presented., Comment: 8 pages, 15 figures; presented at VLVNT08 (Very Large Volume Neutrino Telescope) Workshop, Toulon, France, April, 2008; to appear in NIM-A