DNA Damage in Splenocytes of Mice Exposed to Secondary Radiation Created by 650 MeV Protons Bombarding a Concrete Shielding Barrier.

The proportion of splenocytes with a high level of DNA double-strand breaks was determined in mice exposed to primary and secondary radiation created by bombarding of a concrete barrier (thickness 20, 40, and 80 cm) by 650 MeV protons. The proportion of splenocytes with a high level of DNA double-strand breaks was assessed by flow cytometric analysis of γH2AX+ and TUNEL+ cells. It is shown that concrete barrier can significantly reduce primary proton radiation; the severity of negative biological effects in mice irradiated in the center of the proton beam decreased with increasing the thickness of this barrier. However, the spectrum of secondary radiation changes significantly with increasing the barrier thickness from 20 to 80 cm and the distance from central axis of the beam from 0 to 20 cm, and the proportion of the neutron component increases, which also causes negative biological effects manifesting in a significant (p<0.05) increase in the percentage of splenocytes with a high level of DNA damage in mice irradiated at a distance of 20 cm from the center of the proton beam and receiving relatively low doses (0.10-0.17 Gy).

A new type of ground-based simulator of radiation field inside a spacecraft in deep space.

The problem of full-scale ground-based modeling of cosmic radiation on heavy-ion accelerators for space radiobiology is very urgent. A new type of space radiation simulator at the 56Fe ion beam with energy 1 GeV/n is proposed. The simulator uses rotating converters consisting of segmented targets with varying thicknesses. When a flat uniform field of primary 56Fe ions is used, this design ensures the uniformity of the fields of all secondary particles behind the targets. The proposed setup with four replaceable converters makes it possible to simulate not only the distribution of linear energy transfers of cosmic radiation but also reproduce continuous energy spectra of all charged fragments of the projectile ion from protons to Co. The results of simulation of the internal radiation field inside the habitable module of a spacecraft with a shell of 15 g/cm2 Al, generated by particles of galactic cosmic rays in the solar activity range from 0 to 190 Wolf numbers, are presented.

Fluence-to-effective dose conversion coefficients for male astronauts.

The problem of the reliable estimation of astronauts' radiation exposure doses in deep space is very important and relevant in connection with the accepted space research programmes. The effective dose value based on ICRP Publication 103 presents too conservative an estimate of an astronaut's radiation risk. A more realistic dose can be calculated on the basis of relationships between the radiation quality factor and linear energy transfer or linear energy or Z*2/ß 2, according to the NASA concept. In addition, it is reasonable to use a set of tissue weighting coefficients (normalised relative detriments) that have been averaged over a cohort of working age males similar to the male astronaut cohort. The closest to the male astronauts is the NASA cohort of males aged 30-60 years who have never smoked. The fluence-to-effective dose equivalent conversion coefficients calculated specially for male astronauts are compared. Different approaches to radiation risk estimation for astronauts are discussed.

The ADRON-RM Instrument Onboard the ExoMars Rover.

This overview presents the physical principles, design, measurement capabilities, and summary of planned operations of the autonomous detector of radiation of neutrons onboard rover at Mars (ADRON-RM) on the surface of Mars. ADRON-RM is a Russian project selected for the joint European Space Agency-Roscosmos ExoMars 2020 landing mission. A compact passive neutron spectrometer, ADRON-RM, was designed to study the abundance and distribution of water and neutron absorption elements (such as Cl, Fe, and others) in the martian subsurface along the path of the ExoMars rover. Key Words: Mars exploration-Surface-Neutron Spectroscopy-Water. Astrobiology 17, 585-594.

A comparative study of LaBr3(Ce(3+)) and CeBr3 based gamma-ray spectrometers for planetary remote sensing applications.

The recent availability of large volume cerium bromide crystals raises the possibility of substantially improving gamma-ray spectrometer limiting flux sensitivities over current systems based on the lanthanum tri-halides, e.g., lanthanum bromide and lanthanum chloride, especially for remote sensing, low-level counting applications or any type of measurement characterized by poor signal to noise ratios. The Russian Space Research Institute has developed and manufactured a highly sensitive gamma-ray spectrometer for remote sensing observations of the planet Mercury from the Mercury Polar Orbiter (MPO), which forms part of ESA's BepiColombo mission. The Flight Model (FM) gamma-ray spectrometer is based on a 3-in. single crystal of LaBr3(Ce(3+)) produced in a separate crystal development programme specifically for this mission. During the spectrometers development, manufacturing, and qualification phases, large crystals of CeBr3 became available in a subsequent phase of the same crystal development programme. Consequently, the Flight Spare Model (FSM) gamma-ray spectrometer was retrofitted with a 3-in. CeBr3 crystal and qualified for space. Except for the crystals, the two systems are essentially identical. In this paper, we report on a comparative assessment of the two systems, in terms of their respective spectral properties, as well as their suitability for use in planetary mission with respect to radiation tolerance and their propensity for activation. We also contrast their performance with a Ge detector representative of that flown on MESSENGER and show that: (a) both LaBr3(Ce(3+)) and CeBr3 provide superior detection systems over HPGe in the context of minimally resourced spacecraft and (b) CeBr3 is a more attractive system than LaBr3(Ce(3+)) in terms of sensitivities at lower gamma fluxes. Based on the tests, the FM has now been replaced by the FSM on the BepiColombo spacecraft. Thus, CeBr3 now forms the central gamma-ray detection element on the MPO spacecraft.

Experiment LEND of the NASA Lunar Reconnaissance Orbiter for high-resolution mapping of neutron emission of the Moon.

The scientific objectives of neutron mapping of the Moon are presented as 3 investigation tasks of NASA's Lunar Reconnaissance Orbiter mission. Two tasks focus on mapping hydrogen content over the entire Moon and on testing the presence of water-ice deposits at the bottom of permanently shadowed craters at the lunar poles. The third task corresponds to the determination of neutron contribution to the total radiation dose at an altitude of 50 km above the Moon. We show that the Lunar Exploration Neutron Detector (LEND) will be capable of carrying out all 3 investigations. The design concept of LEND is presented together with results of numerical simulations of the instrument's sensitivity for hydrogen detection. The sensitivity of LEND is shown to be characterized by a hydrogen detection limit of about 100 ppm for a polar reference area with a radius of 5 km. If the presence of ice deposits in polar "cold traps" is confirmed, a unique record of many millions of years of lunar history would be obtained, by which the history of lunar impacts could be discerned from the layers of water ice and dust. Future applications of a LEND-type instrument for Mars orbital observations are also discussed.

The Dynamic Albedo of Neutrons (DAN) experiment for NASA's 2009 Mars Science Laboratory.

We present a summary of the physical principles and design of the Dynamic Albedo of Neutrons (DAN) instrument onboard NASA's 2009 Mars Science Laboratory (MSL) mission. The DAN instrument will use the method of neutron-neutron activation analysis in a space application to study the abundance and depth distribution of water in the martian subsurface along the path of the MSL rover.

[Cytogenetic effects in human blood lymphocytes in vitro after irradiation by protons with 1-GEV energy].

Cytogenetic disorders in peripheral blood lymphocytes of humans were studied in culture following single irradiation by protons with energy of 1 GeV. Doses ranged from 0.05 to 2.0 Gy. A large number of structural damages were observed. Nature of dependence of frequency of such irradiation markers as dicentrics and centric ring was established. Relative biological coefficient of relative energy protons was calculated as 1.2.