Use of pulsed ultraviolet irradiation of elements of the ExoMars-2020 spacecraft landing module to fulfill planetary protection requirements
Abstract
In order to prevent pollution by terrestrial microorganisms of Mars, the landing module (DM) of the ExoMars 2020 spacecraft (SC) should not contain more than 300 bacterial spores/m$ ^{2}$ (in accordance with the recommendations of COSPAR). Considering that not all materials of spacecraft structural elements are compatible with traditional sterilization methods (thermal, radiation, or gas), a method has been proposed and experimentally substantiated for the effective disinfection of open surfaces when combined processing of pulsed high-intensity flows of ultraviolet (UV) radiation of a continuous spectrum and ethanol vapor. The disinfection efficiency of the open surfaces of the materials used in the design of the landing module was studied during their preliminary contamination with microorganisms in the spore form (most resistant to UV radiation) to levels from 10$ ^{5}$ to 10$ ^{6}$ spores/cm$ ^{2}$. The source of UV radiation of the continuous spectrum was a pulsed xenon lamp of the Yanex-2M device. The effectiveness of disinfection of pre-packaged contaminated samples in a transparent and sealed film was also investigated. It was shown that the efficiency obtained in the experiments corresponds to the requirements of planetary protection and does not depend on the type of material used in the design of the landing module, except for porous materials characterized by high hydrophilicity. The required disinfection efficiency was maintained when irradiating elements of complex shape that were irradiated with reflected or scattered light from a flash xenon lamp. The values of energy fluxes (the so-called surface disinfecting doses) and the modes (duration, distance, etc.) of UV-irradiation of surfaces are determined. Recommendations on UV processing of the landing module as a whole and of individual elements of its design are developed. The regulations for maintaining the microbiological cleanliness of the surfaces and air of large-sized cleanrooms at «Lavochkin Research and Production Association» and at the Baikonur Cosmodrome have been worked out.
- Publication:
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43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E2246D