When developing the strategy of long-term interplanetary missions, minimization of risks associated with radiation hazard (for both the spacecraft systems and the crew) in manned expeditions is one of the most important conditions. In order to forecast such risks, one usually estimates the absorbed and equivalent doses that can be received by elements of devices and by astronauts, respectively. To take into account the numerous factors that influence the dose values inside a spacecraft is a laborious problem. The goal of this paper is to describe a technique developed for dose predictions in interplanetary space missions using computer versions of the models of particle fluences for radiation environment and spacecraft construction.In this paper the technique is applied for calculation of absorbed doses onboard the interplanetary space vehicle Fobos-Grunt (under development by the Lavochkin NPO), whose launch is planned in 2009. Currently, there are several alternative scenarios of this mission. One of the basic variants (its characteristics are presented in Table 1) was used to make calculations.The method of predicting the absorbed dose value includes the following four program levels of computation.1. Calculation of energy spectra of particle fluences in the open space which act upon a spacecraft during its flight.2. Calculation of energy spectra of particle fluences in the center of a spherically symmetrical shield.3. Calculation of absorbed and equivalent doses in the center of the spherically symmetrical shield.4. Calculation of local doses taking into account the real structures of the spacecraft.The output data of programs of the preceding level serve as input data for the subsequent level. Computations of the first three levels are realized in a single software package SEREIS developed in Skobeltsyn Institute of Nuclear Physics, MSU [1,2]. At the fourth program level computations are made using an independent software package LocalDose developed in the Federal State Enterprise "Lavochkin NPO" [3].At the first program level the energy spectra Φ i ( E ) of particle fluences are calculated for galactic and solar cosmic rays (GCR and SCR) which act upon a spacecraft on particular segments of its route and throughout the entire flight. For calculation we used two programs computing the particle fluences for GCR and SCR, respectively. They were developed on the basis of computerized versions of the dynamic model of fluences of galactic cosmic rays [4] and the probabilistic model of fluences of solar cosmic rays [5]. These models yield the particle fluence at the Earth's orbit as a function of solar activity. Special corrections are made in new computerized versions of these models in order to take into account the variation of the particle fluence depending on the distance of a spacecraft from the Sun. Each program makes successive step by step computation for a specified trajectory of a spacecraft.

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In the course of operation spacecrafts are exposed to ionizing radiation from outer space. The electronic component base (ECB) used in creating onboard radio-electronic equipment of universal space platforms does not always correspond to the external operating conditions in terms of radiation resistance for some spacecraft orbits due to a number of technical and/or economic reasons. One method to increase the radiation resistance of onboard equipment is to install additional mass protection in the form of screens on the whole equipment or local screens on individual critical radio and electronic components. The article describes the design of additional radiation protection of the geostationary spacecraft scientific equipment complex for adaptation to the radiation conditions of operation in orbits of the “Molniya” type. The solution of the problem involves several preliminary steps, namely: determining the radiation conditions for the spacecraft operation in the target orbit, estimating the local absorbed doses at the locations of the onboard equipment, estimating absorbed doses directly in the electronic component base of the equipment and analyzing the radiation resistance. Designing the radiation complex of scientific equipment was based on the values of the radiation resistance of the equipment and its components, as well as the calculated values of the local absorbed doses in the components

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