RADIATION ENVIRONMENT STUDY DURING PHOBOS SAMPLE RETURN MISSION BY CHARGED PARTICLE TELESCOPE LIULIN-PHOBOS. Ts.P. Dachev 1 , J.V. Semkova 1 , S. Maltchev 1 , B. Tomov 1 , Yu. Matviichuk 1 , R. Koleva 1 , V. Benghin 2 , I. Chernykh 2 , V. Shurshakov 2 , V. Petrov 2 , G. De Angelis 3 1 Solar-Terrestrial Influences Institute, Bulgarian Academy of Sci. (STIL-BAS), Sofia, Bulgaria tdachev@bas.bg ; jsemkova@stil.bas.bg 2 Institute of Biomedical Problems, Russian Academy of Sci. (IBMP-RAS), Moscow, Russia, benghin@pike.net.ru 3 Istituto Superiore di Sanità, Rome, I-00161, Italy, giovanni.deangelis@iss.it Introduction: With regards to the human explora- tion of Mars, the radiation exposures to be received by astronauts in transit to Mars and on the Mars surface have to be assessed including the understanding of the modification of cosmic rays by the Martian atmos- phere and identifying shielding optimisation ap- proaches. Some calculation models [1-3] have been elaborated but still there arelarge uncertainties aboutthe dose evaluation, because of the lack of knowledge of the source term (precise radiation com- position, energy spectrum, flux) as well as the influ- ence of the environment (atmosphere, surface). An- other important issue is the biological effect of cosmic highly energetic particles in the heavy ion component, typically referred to as HZE particles, that is still not well known and is the subject of several research pro- grams at international level [4,5]. HZE particles play a particularly important role in space dosimetry. Those particles, especially iron, have high linear energy transfer (LET) and are highly penetrating, giving them a large potential for radiobiological damage [6]. The “late effects” caused by GCR heavy ions have been identified by the National Research Council [7] as the principal radiation risk to astronauts on extended stays outside LEO. The effective dose expected for an exploratory space mission is very large compared to the effective dose limits recommended by the International Com- mission on Radiological Protection (ICRP) [8] for the general public (1 mSv.year -1 ) and for occupational exposures (20 mSv.year -1 ) and is expected to be higher than the exposure limits recommended by the National Council of Radiation Protection and Measurements (NCRP) [9] for astronauts during exploration missions at low Earth orbit (LEO) (0.5 mSv maximum annual dose to the blood-forming organs). This NCRP report specifies that these limits do not apply to interplanetary missions because of the large uncertainties in predict- ing the risks of late effects from heavy ions. The current models for radiation risk assessment lead to evaluations with very large uncertainties because of the lack of knowledge of: i) the source term (precise radiation composition, energy spectrum, flux); ii) the interactions of cosmic radiation with matter for each particular case, needed for the calculation of shielding and dose in human body and, iii) the biological effects of cosmic particles, especially the HZE particles. Development of techniques and methods for investigation of the radiation hazards during future exploratory missions as well as components of the radiation safety system for manned deep space missions is demanded. Recently the near-Mars charged particles radiation environment was explored by the MARIE experiment aboard the 2001 Mars Odyssey spacecraft [10]. Data have revealed on the one hand that the radiation exposure in the transit period was “approximately double” that which astronauts are receiving on the International Space Station (ISS) and on the other hand that the exposure to the heavy nuclei, up to and including iron nuclei, is “approximately three times” what the astronauts are receiving on the ISS. The obtained dose equivalent in Mars orbit was about 2.5 times larger than on ISS [11]. The GCR dose obtained was about 250 μGy/day, which corresponds to about 0.3 to 0.4 Sv/yr dose equivalent. Because the NASA career limit for astronauts is 1-4 Sv, depending on the age and gender of the individual, it means that a three year mission to Mars and back would put some astronauts in danger of exceeding their career limit. The Liulin-Phobos radiation environment en route and on Phobos surface is described and modeled in a separate LPSC 2009 paper by G. De Angelis. Scientific Objectives of Liulin-Phobos experi- ment: An instrument Liulin-Phobos for a new experi- ment in radiation research is under development to be flown onboard the future Phobos - Soil sample return mission to the satellite of Mars – Phobos. Launch of the spacecraft is scheduled for late 2009 [12]. The main goal of the Liulin-Phobos experiment is the investigation of the radiation environment and doses in the heliosphere at distances of 1 to 1.5 AU from the Sun and in the near-Mars space. This research will be used for the assessment of radiation risk to the crewmembers of future exploratory flights. Description of Liulin-Phobos experiment: The instrumentation will qualitatively and quantitatively characterize, in terms of dose rate and linear energy 1297.pdf 40th Lunar and Planetary Science Conference (2009)