The article provides a brief description of the Liulin-MO dosimeter, which is part of the FREND (Fine Resolution Epithermal Neutron Detector) device installed on the TGO (Trace Gas Orbiter) spacecraft of the ExoMars-2016 mission. Since April 2018, TGO has been operating in orbit around Mars. Data are presented on the radiation environment in the orbit of Mars during the decline phase of the 24th cycle of solar activity and the growth phase of the 25th cycle. During the period under review, a maximum flux and dose rate due to galactic cosmic rays (GCR) were observed. Between July 2021 and March 2023, the Liulin-MO dosimeter recorded eight increases in particle fluxes and dose rates from solar proton events (SPEs). Data are presented on the radiation environment during the SPE in Mars orbit in July 2021–March 2022, when Mars was on the opposite side of the Sun from Earth. A comparison is made of particle fluxes measured in orbits around the Earth and Mars.

The paper presents the results of the analysis of the neutron component of the radiation background on Mars in the Gale crater, where the NASA Curiosity rover conducts its research. Numerical estimates have shown that the effective dose rate for neutrons at the maximum flux of galactic cosmic rays varies along the rover path by 20% in the range of 92–108 μSv/day. This variation is mainly driven by the variable content of subsurface water, which ranges from 0.5 to 5% mass fraction along the rover path. The estimates obtained are comparable with the measurements of the RAD radiation dosimeter. The comparison with doses from charged particles shows that the contribution of the neutron component on the surface of Mars to the total dose with no radiation protection is 10%, which should be taken into account when planning manned missions to Mars.

This paper presents the results of the analysis of data from the BTN-Neutron space experiment carried out onboard the Russian module Zvezda, which is part of the International Space Station . The long observation period from 2008 to 2019 covers the end of the 23rd and almost all of the 24th solar cycle. This made it possible to estimate the amplitude of long-period variations of the neutron background outside the ISS due to solar modulation of galactic cosmic rays. For equatorial regions with a high geomagnetic-cutoff index, it does not exceed 10%, while the neutron background changes by almost 1.5–2 times in high-latitude regions around the Earth’s magnetic poles and the South Atlantic Magnetic Anomaly. For the periods of minimum and maximum solar activity within the 24th solar cycle, according to the BTN-Neutron experiment, maps of the distribution of the neutron-component power were constructed and the average neutron-dose rates that the cosmonauts could receive during these periods were estimated. It was shown that, for maximum and minimum solar activity, the average neutron dose rate varies from 25 to 35 µSv/day for neutrons with energies below 15 MeV.

Space radiation has been monitored successfully using the Radiation Risks Radiometer-Dosimeter (R3D) installed at the ESA EXPOSE-R (R3DR) facility outside of the Russian Zvezda module of the International Space Station (ISS) between March 2009 and January 2011. R3DR is a Liulin type spectrometer–dosimeter with a single Si PIN detector 2cm2 of area and 0.3mm thick. The R3DR instrument accumulated about 2 million measurements of the absorbed dose rate and flux of 10s resolution. The total external and internal shielding before the detector of R3DR device is 0.41gcm−2. The calculated stopping energy of normally incident particles to the detector is 0.78MeV for electrons and 15.8MeV for protons. After the Coronal Mass Ejection (CME) at 09:54 UTC on 3 April 2010, a shock was observed at the ACE spacecraft at 0756 UTC on 5 April, which led to a sudden impulse on Earth at 08:26 UTC. Nevertheless, while the magnetic substorms on 5 and 6 of April were moderate; the second largest in history of GOES fluence of electrons with energy >2MeV was measured. The R3DR data show a relatively small amount of relativistic electrons on 5 April. The maximum dose rate of 2323μGyday−1 was reached on 7 April; by 9 April, a dose of 6600μGy was accumulated. By the end of the period on 7 May 2010 a total dose of 11,587μGy was absorbed. Our data were compared with AE-8 MIN, CRESS and ESA-SEE1 models using SPENVIS and with similar observations on American, Japanese and Russian satellites.

The paper presents observations of relativistic electron precipitations (REP) on the International Space Station (ISS) obtained by three Bulgarian-built instruments flown in 2001 and 2008–2010. The first data are from the Liulin-E094 instrument flown in May–August 2001 inside the US laboratory module of the ISS. Next the time profiles of the REP-generated daily fluences and the absorbed doses at the orbit of ISS during the period February 2008–August 2010 are analyzed in dependence of the daily Ap index and compared with the daily relativistic electron fluence with energies of more than 2MeV measured by the GOES. The REP in April 2010 being the second largest in GOES history (with a >2MeV electron fluence event) is specially studied.

The main purpose of Liulin-type spectrometry-dosimetry instruments (LSDIs) is cosmic radiation monitoring at the workplaces. An LSDI functionally is a low mass, low power consumption or battery-operated dosemeter. LSDIs were calibrated in a wide range of radiation fields, including radiation sources, proton and heavy-ion accelerators and CERN-EC high-energy reference field. Since 2000, LSDIs have been used in the scientific programmes of four manned space flights on the American Laboratory and ESA Columbus modules and on the Russian segment of the International Space Station, one Moon spacecraft and three spacecraft around the Earth, one rocket, two balloons and many aircraft flights. In addition to relative low price, LSDIs have proved their ability to qualify the radiation field on the ground and on the above-mentioned carriers.

Liulin-type spectrometers can characterise the type of predominant particles and their energy in the radiation environment. The results from calibrations and space and aircraft experiments revealed that the most informative is by the shape of the deposited energy spectrum. Spectra generated by galactic cosmic rays (GCR) protons and their secondaries look like straight lines in the coordinates deposited energy/deposited per channel dose rate. The position of the maximum of the deposited energy spectra depends on the incident energy of the incoming protons. Spectra generated by relativistic electrons in the outer radiation belt have a maximum in the first channels. For higher energy depositions, these spectra are similar to the GCR spectra. All types of spectra have a knee close to 6.3 MeV of deposited energy, which corresponds to the stopping energy of protons in the detector.

The absorbed dose rates from Galactic Cosmic Rays (GCR) and their secondary were continuously measured at aircraft altitudes with Liulin type spectrometer since 2001. These measurements were performed in cooperation with Czech Airlines (CSA). The data cover the declining phase of the 23 solar cycle and show increase from about 1.7to 2.5 μGy/h. The dose rates from GCR were also independently measured with analogical instruments onboard following spacecraft: International Space Station in 2001 and 2008-2009; Foton-M2/M3 satellites in June 2005 and September 2007 respectively and on Indian Chandrayaan-1 satellite in 2008-2009. The dose rates in LEO and relatively high latitudes increase from about 6 to 12 μGy/h. Obtained experimental data are compared with computational models.

CHANDRAYYAN-1 SATELLITE AND A COMPARISON WITH THE RADOM EXPERIMENT DATA G. De Angelis, Ts.P. Dachev, B. Tomov, Yu. Matviichuk, Pl. Dimitrov, F. Spurny, S. Vadawale Istituto Superiore di Sanità, Rome, I-00161, Italy (Mail Code CNESPS, Istituto Superiore di Sanità, Viale Regina Elena 299, Rome, I-00161, Italy, giovanni.deangelis@iss.it), Solar-Terrestrial Influences Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria, tdachev@bas.bg, Nuclear Physics Institute, Czech Academy of Sciences, Czech Republic, spurny@ujf.cas.cz, Physical Research Laboratory, Astronomy & Astrophysics Division, Ahmedabad, India, svadawale@gmail.com

Solar and space radiation have been monitored using the R3D-B2 radiation risks radiometer-dosimeter on board a recent space flight on the Russian satellite Foton M2 within the ESA Biopan 5 facility mounted on the outside of the satellite exposed to space conditions. The solar radiation has been assayed in four wavelength bands (UV-C, 170–280nm, UV-B, 280–315nm), UV-A (315–400nm) and PAR (photosynthetic active radiation, 400–700nm). The data show an increasing tumbling rotation of the satellite during the mission. The photodiodes do not show a cosine response to the incident light which has been corrected. After calibration of the signals using the extraterrestrial spectrum, doses have been calculated for each orbit, for each day and for the total mission as basic data for the biological material which has been exposed in parallel in the Biopan facility. Cosmic ionizing radiation has been monitored and separated in 256 deposited energy spectra, which were further used for determination of the absorbed dose rate and flux. Basic data tables were prepared to be used by other Biopan 5 experiments. The paper summarizes the results for the Earth radiation environment at the altitude (262–304km) of the Foton M2 spacecraft. Comparisons with the predictions of NASA Earth radiation environment experimental models AE-8 and AP-8, and the PSB97 model are also presented, which calculate the fluxes of ionizing radiation from a simulation. AP-8 is a model for trapped radiation.

INSTRUMENT ON INDIAN CHANDRAYYAN-1 SATELLITE. PRELIMINARY RESULTS. Ts.P. Dachev, B.T. Tomov, Yu.N. Matviichuk, Pl.S. Dimitrov, G. De Angelis, F. Spurny, S. Vadawale Solar-Terrestrial Influences Institute, Bulgarian Academy of sciences, Sofia, Bulgaria, tdachev@bas.bg; Istituto Superiore di Sanita, Rome, I-00161, Italy, giovanni.deangelis@iss.it) Nuclear Physics Institute, Czech Academy of Sciences, Czech Republic, spurny@ujf.cas.cz Physical Research Laboratory, Astronomy & Astrophysics Division, Ahmedabad, India, svadawale@gmail.com

CHARGED PARTICLE TELESCOPE LIULIN-PHOBOS. Ts.P. Dachev, J.V. Semkova, S. Maltchev, B. Tomov, Yu. Matviichuk, R. Koleva, V. Benghin, I. Chernykh, V. Shurshakov, V. Petrov, G. De Angelis Solar-Terrestrial Influences Institute, Bulgarian Academy of Sci. (STIL-BAS), Sofia, Bulgaria tdachev@bas.bg; jsemkova@stil.bas.bg Institute of Biomedical Problems, Russian Academy of Sci. (IBMP-RAS), Moscow, Russia, benghin@pike.net.ru Istituto Superiore di Sanità, Rome, I-00161, Italy, giovanni.deangelis@iss.it

The radiation protection is one of the two NASA highest concerns priorities [1]. In view of manned missions targeted to Mars [2], for which radiation exposure is one of the greatest challenges [3], it is fundamental to determine particle fluxes and doses at any time and at any location and elevation on and around Mars [4]. With this goal in mind, models of radiation environment induced by Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE) on Mars and Phobos have been developed [5]. The work is de-scribed [6] as incoming cosmic ray [7-9] and solar events [5-6] primary particles rescaled for Mars condi-tions then transported through the atmosphere down to the surface, with topography and backscattering taken into account, then through the subsurface layers, with volatile content and backscattering taken into account, eventually again through the atmosphere, and interact-ing with some targets described as material layers. Models have been developed for the surface of the satellites Phobos, as well as for the cruise phase. These results for Mars and Phobos Radiation Environment have been obtained in the framework of the LIULIN-PHOBOS investigation that will be onboard the PHOBOS-GRUNT mission by the Russian Space Agency RKA. The LIULIN-PHOBOS investigation is described in another LPSC 2009 paper by Ts. Dachev.

During the analysis of the R3D-B2/B3 data from the flights of the Foton M2/M3 satellites were obtained new type deposited energy spectra with very high count rates in the first few channels. The count rate in higher deposited energy channels was similar to the usual GCR count rate. It was found that these types of spectra are localized at high latitudes where other radiation belt particles are expected and that the specific dose per particle is less than 0.7 nGy.cm 2 .particle -1 . On the base of this and on the base of search of the literature we considered that only electrons with energy higher than few MeV are able to produce this type of spectra. When after March 2008 we start to analyse the data from the R3DE instrument situated at EuTEF facility of European Columbus module of ISS we was happy to found very similar spectra but even with higher count rate because of smaller shielding of it. The paper analyse all data where at the 3 carriers relativistic electrons are observed. The measured absolute maximums of the doses generated by relativistic electrons are distributed as follows: 304 μGy.h -1 behind 1.75 g.cm -2 shielding at Foton M2, 2314 μGy.h -1 behind 0.71 g/cm 2 shielding at Foton M3 and 19195 μGy.h -1 (Flux is 8363 cm -2 s -1 ) behind les than 0.4 g/cm 2 shielding at ISS.