The image quality of high-definition television (HDTV) cameras and camcorders for space activity is degraded by the presence of permanent bright pixels (so-called “white defects”) due to space radiation. We studied the space radiation damage to HDTV charge-coupled devices (CCDs; 2 × 106 pixels per chip) loaded in the Russian service module (SM) of the International Space Station (ISS) for 71 days, 256 days and 446 days. We used the “Passive Dosimeter for Lifescience Experiments in Space” (PADLES), which consists of CR-39 plastic nuclear track detectors (PNTDs) and thermoluminescent dosimeters, to measure space radiation doses received by the HDTV CCDs in the SM during loading periods. The average production rates of white defects for output voltage greater than 0.5 mV were 2.366 ± 0.055 pixels/day in Si and 5.213 ± 0.071 pixels/mGy in Si. We also investigated the correlation between the position of the white defects and tracks of high-energy particles with LET∞,Si of approximately 300 keV/μm or more using stacks of CR-39 PNTDs and the HDTV CCD chips. We found that approximately 30% of these high-energy high-LET particles coincided with the position of white defects on the HDTV CCDs in the SM.
Research Containing: Radiation exposure
Tests of shielding effectiveness of Kevlar and Nextel onboard the International Space Station and the Foton-M3 capsule
Radiation assessment and protection in space is the first step in planning future missions to the Moon and Mars, where mission and number of space travelers will increase and the protection of the geomagnetic shielding against the cosmic radiation will be absent. In this framework, the shielding effectiveness of two flexible materials, Kevlar and Nextel, were tested, which are largely used in the construction of spacecrafts. Accelerator-based tests clearly demonstrated that Kevlar is an excellent shield for heavy ions, close to polyethylene, whereas Nextel shows poor shielding characteristics. Measurements on flight performed onboard of the International Space Station and of the Foton-M3 capsule have been carried out with special attention to the neutron component; shielded and unshielded detectors (thermoluminescence dosemeters, bubble detectors) were exposed to a real radiation environment to test the shielding properties of the materials under study. The results indicate no significant effects of shielding, suggesting that thin shields in low-Earth Orbit have little effect on absorbed dose.
Several passive detectors were used to estimate dosimetry and microdosimetry characteristics of radiation field onboard spacecraft, namely: thermoluminescent detectors (TLDs), mainly to appreciate the contribution of radiation with low-linear energy transfer (LET); Si diode, to try to establish the contribution of fast neutrons; an LET spectrometer based on the chemically etched polyallyldiglycolcarbonate etched track detectors (PADC-TEDs). Detectors have been exposed onboard MIR and International Space Station (ISS) since 1997, they were also used during the MESSAGE 2 biological experiment, October 2003. The results are presented, analysed and discussed. Particular attention is devoted to the possibility of estimating neutron contribution based on data obtained with PADC-TED spectrometer of LET.
Collagen and silk materials, in neat forms and as silica composites, were flown for 18 months on the International Space Station [Materials International Space Station Experiment (MISSE)-6] to assess the impact of space radiation on structure and function. As natural biomaterials, the impact of the space environment on films of these proteins was investigated to understand fundamental changes in structure and function related to the future utility in materials and medicine in space environments. About 15% of the film surfaces were etched by heavy ionizing particles such as atomic oxygen, the major component of the low-Earth orbit space environment. Unexpectedly, more than 80% of the silk and collagen materials were chemically crosslinked by space radiation. These findings are critical for designing next-generation biocompatible materials for contact with living systems in space environments, where the effects of heavy ionizing particles and other cosmic radiation need to be considered.
DOsimetry of BIological EXperiments in SPace (DOBIES) with luminescence (OSL and TL) and track etch detectors
The objective of the “DOsimetry of BIological EXperiments in SPace” (DOBIES) project is to develop a standard dosimetric method as a combination of different techniques to estimate absorbed dose, dose equivalent, and linear energy transfer (LET) spectrum in biological samples in space experiments. The detectors investigated in the project include various types of thermoluminescence detectors (TLDs), such as LiF:Mg,Ti, LiF:Mg,Cu,P, CaSO 4 :Dy, as well as Al 2 O 3 :C used as TLD and optically stimulated luminescence detectors (OSLDs), and track-etch detectors (TED). This paper describes the DOBIES project and reports preliminary results obtained during the BASE-A experiment carried out at the International Space Station (ISS) in September, 2006. The results are compared to data from previous space exposures carried out by the members of the DOBIES project.
Barley seeds were exposed to outer space for 13 months in a vented metal container without a climate control system to assess the risk of physiological and genetic mutation during long-term storage in space. The space-stored seeds (S0 generation), with an 82% germination rate in 50 seeds, lost about 20% of their weight after the exposure. The germinated seeds showed normal growth, heading, and ripening. The harvested seeds (S1 generation) also germinated and reproduced (S2 generation) as did the ground-stored seeds. The culm length, ear length, number of seed, grain weight, and fertility of the plants from the space-stored seeds were not significantly different from those of the ground-stored seeds in each of the S0 and S1 generation. Furthermore, the S1 and S2 space-stored seeds respectively showed similar β-glucan content to those of the ground-stored seeds. Amplified fragment length polymorphism analysis with 16 primer combinations showed no specific fragment that appears or disappears significantly in the DNA isolated from the barley grown from the space-stored seeds. Though these data are derived from nine S0 space-stored seeds in a single exposure experiment, the results demonstrate the preservation of barley seeds in outer space for 13 months without phenotypic or genotypic changes and with healthy and vigorous growth in space.
This article presents the results of a systematic literature review to locate peer-reviewed journal articles that offer equivalent or absorbed radiation dose measurements for locations in outer space. The review utilized three separate keyword searches, one using MEDLINE and 2 using Google Scholar. The queries returned a total of 3,779 potential source documents, 819 of which were screened for inclusion. The final article set contained 43 articles. The articles were all in English though they were contributed by authors from 10 different nations. The United States was the most frequent contributor followed by Germany. The articles provided data from every manned US space program except Project Mercury, as well as from 3 Soviet space stations. The article pool displayed recency in publication, with a majority of the articles published in 1990 or later. It is speculated that this is due to a preference for reporting results in technical reports and conference abstracts in the 1960s and 1970s. The shift from research conducted by contractors to the National Aeronautics and Space Administration (NASA) to partnerships with civilian scientists at universities may be responsible for the increased frequency of publication in peer-reviewed journals. The collection of articles provides more than 550 dose measurements for spacecraft and extra-vehicular activity in 42 combinations of inclination and altitude in low Earth orbit. The articles also provide 57 measurements for lunar missions. The most often sampled locations were those that had space stations, followed by measurements taken aboard the Gemini capsules and the Space Shuttle fleet. This review demonstrates that dosimetric data exist in sufficient abundance that they might be further synthesized into useful dose estimation models and tools. Such tools could be of great utility in mission planning and epidemiological studies of the effects of space radiation on human health.
Cytogenetic damage was assessed in blood lymphocytes from 16 astronauts before and after they participated in long-duration space missions of 3 months or more. The frequency of chromosome damage was measured by fluorescence in situ hybridization (FISH) chromosome painting before flight and at various intervals from a few days to many months after return from the mission. For all individuals, the frequency of chromosome exchanges measured within a month of return from space was higher than their preflight yield. However, some individuals showed a temporal decline in chromosome damage with time after flight. Statistical analysis using combined data for all astronauts indicated a significant overall decreasing trend in total chromosome exchanges with time after flight, although this trend was not seen for all astronauts and the yield of chromosome damage in some individuals actually increased with time after flight. The decreasing trend in total exchanges was slightly more significant when statistical analysis was restricted to data collected more than 220 days after return from flight. When analysis was restricted to data collected within 220 days of return from the mission there was no relationship between total exchanges and time. Translocation yields varied more between astronauts and there was only a slight non-significant decrease with time after flight that was similar for both later and earlier sampling times.
We review methods and data used for determining astronaut organ dose equivalents on past space missions including Apollo, Skylab, Space Shuttle, NASA-Mir, and International Space Station (ISS). Expectations for future lunar missions are also described. Physical measurements of space radiation include the absorbed dose, dose equivalent, and linear energy transfer (LET) spectra, or a related quantity, the lineal energy (y) spectra that is measured by a tissue equivalent proportional counter (TEPC). These data are used in conjunction with space radiation transport models to project organ specific doses used in cancer and other risk projection models. Biodosimetry data from Mir, STS, and ISS missions provide an alternative estimate of organ dose equivalents based on chromosome aberrations. The physical environments inside spacecraft are currently well understood with errors in organ dose projections estimated as less than plus or minus 15%, however understanding the biological risks from space radiation remains a difficult problem because of the many radiation types including protons, heavy ions, and secondary neutrons for which there are no human data to estimate risks. The accuracy of projections of organ dose equivalents described here must be supplemented with research on the health risks of space exposure to properly assess crew safety for exploration missions.
NASCA Report 2: Longitudinal Study of Relationship of Exposure to Space Radiation and Risk of Lens Opacity
The NASA Study of Cataract in Astronauts (NASCA) was designed to measure the impact of exposure to space radiation on progression rates of cortical, nuclear, and posterior subcapsular cataract in U.S. astronauts who have flown in space and comparison groups of astronauts who had not flown in space, and subjects with a history of military aviation. We present our analyses of 5 years of data with an average of 3.8 exams per subject. All subjects had digital lens images with the Nidek EAS 1000 Lens Imaging System. Because of high variability and skewness of opacity measures, nonparametric methods were used to test for association between rates of opacification and space radiation exposure. First, median regression was used to collapse longitudinal data into robust estimates of progression rates (opacity severity compare to time for each eye of each subject). To quantify and test for a radiation effect, median regression with the dependent variable being the maximum of the two slopes (OD and OS) per subject was then used, adjusting for the confounding variables of age, nutritional, and sun-exposure histories. Median regression showed evidence of an association between the rate of cortical progression in the worse eye with radiation dose and age. The estimated median progression rate from space radiation being 0.25 ± 0.13% lens area/Sv/year (P = 0.062). We found no relationship between radiation exposure and progression of aggregate area of posterior subcapsular cataract or nuclear progression rates. However, longer follow-up may be needed to further understand any impact of space radiation on progression rates for posterior subcapsular cataracts and nuclear cataracts, and to characterize changes to visual acuity.