New results for the space radiation environment of MIR space station obtained by Liulin dosimeter-radiometer. Comparison with LET spectrometer NAUSICAA

Since 1988 high sensitivity semiconductor dosimeter-radiometer “Liulin” worked on board of MIR space station. Device measured the absorbed dose rate and the flux of penetrating particles. The analysis of the data hows the following new results:

In October 1989 and after March 24, 1991, two additional stable maximums in flux channel were observed in the southern-eastern part of South Atlantic Anomaly (SAA). These two maximums existed at least several months and seem to be due to trapped high energy electron and proton fluxes. In April 1991 additional maximums were localized in the following geographical coordinates regions: LATITUDE = (−35 °)–(−50 °) LONGITUDE = 332 ° − 16 ° and lat.(−46 °)–(−52 °) long. 360 ° − 60 °. Additional maximums diffusion occurs inside radiation belt. Appearance of these maximums seems to be closely connected with preceding powerful solar proton events and associated geomagnetic dynamics of new belt disturbances. After the series of solar proton events in June 1991 we observed significant enhancement of this new radiation belt formation. To achieve sufficient accuracy of dose rate predictions in low Earth orbits the structure and dynamics of new belt should be carefully analyzed to be included in a new environment model.

From the inter comparison of the data from “Liulin” and French developed tissue equivalent LET spectrometer NAUSICAA in the time period August–November 1992 we come to the following conclusions: Mainly there is good agreement between both data sets for absorbed dose in the region of SAA; Different situation of the instruments on the station can explain the cases when differences up to 2 times are observed; At high latitudes usually the tissue equivalent absorbed dose observations are 2 times larger than “Liulin” doses.     

Proposal for a new radiation dose control system for future manned space flights

Radiation risk on a future long-duration manned space mission appears to be one of the basic factors in planning and designing the mission. Since 1988 different active dosimetric investigations has been performed on board the MIR space station by the Bulgarian-Russian dosimeter-radiometer LIULIN and French tissue-equivalent proportional counters CIRCE and NAUSICAA. A joint French-Bulgarian-Russian dosimetry experiment and the dosimetry-radiometry system RADIUS-MD have been developed for the future MARS-96 mission. On the base of the results and experience of these investigations a conception for a new radiation dose control system for the future orbital stations, lunar bases and interplanetary space ships is proposed. The proposed system which consists of different instruments will allow personal radiation control for crew members, radiation monitoring inside and outside each habitat, analysis and forecasting of the situation and will suggest procedures to minimize the radiation risk.     

Changes in symbiotic and associative interrelations in a higher plant-bacterial system during space flight.

The miniature cenosis consisting of the water fern Azolla with its associated symbiotic nitrogen-fixing cyanobacterium Anabaena and the concomitant bacteria was investigated. Ecological closure was shown to produce sharp quantitative and qualitative changes in the number and type of concomitant bacteria. Changes in the distribution of bacterial types grown on beef-extract broth after space flight were recorded. Anabaena azollae underwent the most significant changes under spaceflight conditions. Its cell number per Azolla biomass unit increased substantially. Thus closure of cenosis resulted in a weakening of control over microbial development by Azolla. This tendency was augmented by spaceflight factors. Reduction in control exerted by macro-organisms over development of associated micro-organisms must be taken into account in constructing closed ecological systems in the state of weightlessness.