[Show abstract][Hide abstract] ABSTRACT: A reliable radiation risk assessment in space is a mandatory step for the development of countermeasures and long-duration mission planning in human spaceflight. Research in radiobiology provides information about possible risks linked to radiation. In addition, for a meaningful risk evaluation, the radiation exposure has to be assessed to a sufficient level of accuracy. Consequently, both the radiation models predicting the risks and the measurements used to validate such models must have an equivalent precision. Corresponding measurements can be performed both with passive and active devices. The former is easier to handle, cheaper, lighter, and smaller but they measure neither the time dependence of the radiation environment nor some of the details useful for a comprehensive radiation risk assessment. Active detectors provide most of these details and have been extensively used in the International Space Station. To easily access such an amount of data, a single point access is becoming essential. This review presents an ongoing work on the development of a tool that allows obtaining information about all relevant measurements performed with active detectors providing reliable inputs for radiation model validation.
Preview · Article · Dec 2015 · Frontiers in Oncology
[Show abstract][Hide abstract] ABSTRACT: The project ALTEA-shield/survey is part of an European Space Agency (ESA) - ILSRA (international Life Science Research Announcement) program and provides a detailed study of the international Space Station (ISS) (USLab and partly Columbus) radiation environment. The experiment spans over 2 years, from September 20, 2010 to September 30, 2012, for a total of about 1.5 years of effective measurements. The ALTEA detector system measures all heavy ions above helium and, to a limited extent, hydrogen and helium (respectively, in 25 Mev-45 MeV and 25 MeV/n-250 MeV/n energy windows) while tracking every individual particle. It measures independently the radiation along the three ISS coordinate axes. The data presented consist of flux, dose, and dose equivalent over the time of investigation, at the different surveyed locations. Data are selected from the different geographic regions (low and high latitudes and South Atlantic Anomaly, SAA). Even with a limited acceptance window for the proton contribution, the flux/dose/dose equivalent results as well as the radiation spectra provide information on how the radiation risks change in the different surveyed sites. The large changes in radiation environment found among the measured sites, due to the different shield/mass distribution, require a detailed Computer-Aided Design (CAD) model to be used together with these measurements for the validation of radiation models in space habitats. Altitude also affects measured radiation, especially in the SAA. In the period of measurements, the altitude (averaged over each minute) ranged from 339 km to 447 km. Measurements show the significant shielding effect of the ISS truss, responsible for a consistent amount of reduction in dose equivalent (and so in radiation quality). Measured Galactic Cosmic Ray (GCR) dose rates at high latitude range from 0.354 ± 0.002 nGy/s to 0.770 ± 0.006 nGy/s while dose equivalent from 1.21 ± 0.04 nSv/s to 6.05 ± 0.09 nSv/s. The radiation variation over the SAA is studied. Even with the reduced proton sensitivity, the high day-by-day variability, as well as the strong altitude dependence is clearly observed. The ability of filtering out this contribution from the data is presented as a tool to construct a radiation data set well mimicking deep space radiation, useful for model validations and improvements.
No preview · Article · Dec 2015 · Journal of Space Weather and Space Climate
[Show abstract][Hide abstract] ABSTRACT: Context. Solar activity poses substantial risk for astronauts of the International Space Station (ISS) both on board and during extravehicular activity. An accurate assessment of the charged radiation flux in space habitats is necessary to determine the risk and the specific type of radiation exposure of ISS crew members, and to develop ways to protect future crews for planetary missions, even in case of high solar activity. Aims. To reduce the present-day uncertainties about the nature and magnitude of the particle fluxes in space habitats during a solar event, it is fundamental to measure those fluxes in situ. Methods. The ALTEA (Anomalous Long Term Effects on Astronauts) experiment on board the ISS is an active detector composed of six silicon telescopes and is able to follow the dynamics of the radiation flux. During its operation in 2012 a number of flux peaks were detected in correspondence with solar events. Results. We present in this work an analysis of the ALTEA data measured during the March 7th, 2012 solar event, produced by NOAA AR11429. Conclusions. During this event, the flux was enhanced tenfold with respect to "quiet Sun'' conditions, producing strong dose increases at high geomagnetic latitudes.
No preview · Article · May 2014 · Journal of Space Weather and Space Climate
[Show abstract][Hide abstract] ABSTRACT: High-energy charged particles represent a severe radiation risk for astronauts and spacecrafts and could damage ground critical infrastructures related to space services. Different natural sources are the origin of these particles, among them galactic cosmic rays, solar energetic particles and particles trapped in radiation belts. Solar particle events (SPE) consist in the emission of high-energy protons, alpha-particles, electrons and heavier particles from solar flares or shocks driven by solar plasma propagating through the corona and interplanetary space. Ground-level enhancements (GLE) are rare solar events in which particles are accelerated to near relativistic energies and affect space and ground-based infrastructures. During the current solar cycle 24 a single GLE event was recorded on May 17th, 2012 associated with an M5.1-class solar flare. The investigation of such a special class of solar events permits us to measure conditions in space critical to both scientific and operational research. This event, classified as GLE71, was detected on board the International Space Station (ISS) by the active particle detectors of the ALTEA (Anomalous Long Term Effects in Astronauts) experiment. The collected data permit us to study the radiation environment inside the ISS. In this work we present the first results of the analysis of data acquired by ALTEA detectors during GLE71 associated with an M5.1-class solar flare. We estimate the energy loss spectrum of the solar particles and evaluate the contribution to the total exposure of ISS astronauts to solar high-energy charged particles.
Full-text · Article · May 2014 · Journal of Space Weather and Space Climate
[Show abstract][Hide abstract] ABSTRACT: The study and optimization of material effectiveness as radiation shield is a mandatory step toward human space exploration. Passive radiation shielding is one of the most important element in the entire radiation countermeasures package.
Crewmembers will never experience direct exposure to space radiation; they will be either inside some shelter (the spacecraft, a ‘base’) or in an EVA (Extra Vehicular Activity) suit. Understanding the radiation shielding features of materials is therefore an important step toward an optimization of shelters and suits construction in the quest for an integrated solution for radiation countermeasures.
Materials are usually tested for their radiation shielding effectiveness first with Monte Carlo simulations, then on ground, using particle accelerators and a number of specific ions known to be abundant in space, and finally in space.
Highly hydrogenated materials perform best as radiation shields. Polyethylene is right now seen as the material that merges a high level of hydrogenation, an easiness of handling and machining as well as an affordable cost, and it is often referred as a sort of ‘standard’ to which compare other materials' effectiveness.
Kevlar has recently shown very interesting radiation shielding properties, and it is also known to have important characteristics toward debris shielding, and can be used, for example, in space suits.
We have measured in the ISS the effectiveness of polyethylene and kevlar using three detectors of the ALTEA system [
3] from 8 June 2012 to 13 November 2012, in Express Rack 3 in Columbus. These active detectors are able to provide the radiation quality parameters in any orbital region; being identical, they are also suitable to be used in parallel (one for the unshielded baseline, two measuring radiation with two different amounts of the same material: 5 and 10 g/cm2).
A strong similarity of the shielding behavior between polyethylene and kevlar is documented. We measured shielding providing as much as ∼40% reduction for high Z ions. In Fig. 1, the integrated behavior (3 ≤LET ≤ 350 keV/µm) is shown (ratios with the baseline measurements with no shield) both for polyethylene and kevlar, in flux, dose and dose equivalent.
The measured reductions in dose for the 10 g/cm2 shields for high LET (>50 keV/µm, not shown in the figure) are in agreement with what found in accelerator measurements (Fe, 1 GeV) . The thinner shielding (5 g/cm2) in our measurements performs ∼2% better (in unit areal density).
Fig. 1.Integrated behavior (3 ≤ LET ≤ 350 keV/μm) of Flux, Dose and Equivalent Dose. The ratios with the baseline measurements with no shield are shown, both for Kevlar and Polyethylene as measured with the two different material thicknesses.
Full-text · Article · Mar 2014 · Journal of Radiation Research
[Show abstract][Hide abstract] ABSTRACT: The Sileye3/Alteino experiment is devoted to the investigation of the light flash phenomenon and particle composition of the cosmic ray spectrum inside the ISS. The particle detector is a silicon telescope consisting of eight planes, each divided into 32 strips. Data acquisition was initiated in 2002 in the Russian Pirs module. The data on nuclei from C to Fe in the energy range above about 60 MeV/n presented here were taken as part of the ESA Altcriss project [
1] from late 2005 through 2007. Here we report on LET, from different locations and orientations, in both the Pirs and Zvezda modules. Taking solar modulation into account the results are in agreement with ALTEA measurements from USLab [
2]. To convert the energy deposition in Si to the equivalent in water, the logarithmic relation between LET in Si and water adopted from [
3]. In Fig. 1, the LET spectra in water for Alteino and ALTEA are compared with DOSTEL spectrum from 2001 [
4], and we see a good overall agreement. We are currently in the process of preparing a detailed paper on the dose and dose equivalent rates in different places inside the Zvezda and Pirs modules and a novel analysis of the contribution to the different doses as a function of strip hit multiplicity.Fig. 1.LET spectra in water from Alteino (red triangle), ALTEA (black diamond) [
2], DOSTEL 2001 (solid line) [
Full-text · Article · Mar 2014 · Journal of Radiation Research
[Show abstract][Hide abstract] ABSTRACT: Exposure to space radiation may have impacts on brain function, either during or following missions. It is most important
to determine how low doses of protons and high-LET irradiation elicit changes in brain function. Within this framework, the
role of oxidative stress should also be assessed, as well as other possible interaction mechanisms involving, e.g., genetic,
environmental, and sex-dependent risk factors. The hippocampus is particularly susceptible to radiation. It plays an essential
role in memory formation and consolidation and is one of the most investigated brain components for its responses to radiation.
The hippocampus is also one of the first brain structures to be damaged in the pathogenesis of Alzheimer's disease, an important
potential late impairment following irradiation. In ‘Section 3: CNS risk’, six papers have been presented focused on these
issues. For details the reader is directed to the specific papers. Here a very short summary follows.
Preview · Article · Mar 2014 · Journal of Radiation Research
[Show abstract][Hide abstract] ABSTRACT: In this work we present data from the Sileye-3/Alteino detector on board the International Space Station (ISS), which was gathered following a recalibration after several years in orbit. We also measure the relative nuclei abundance and integrated flux, which were normalized to the solar modulation values of August 2007. The measurements were made at different locations of the Russian part of the ISS. The relative nuclear abundances of C to Fe in relation to C, in an energy range above ≃ 60 MeV/n, shows high levels of odd Z particles inside the ISS and an under-abundance of C and O compared with the galactic spectrum, as presented by Simpson in 1983. In addition, the values of the integrated flux varies primarily according to location and detector orientation. An additional polyethylene shield also reduces the flux, although in a lower amount than changes in the orientation of the telescope. Data were taken as part of the ESA ALTCRISS project from late 2005 through to 2007.
No preview · Article · Jan 2014 · Journal of Physics G Nuclear and Particle Physics
[Show abstract][Hide abstract] ABSTRACT: In this work we present data on linear energy transfer (LET), dose and dose equivalent rates from different locations of the Russian part of the International Space Station (ISS) measured by the Sileye-3/Alteino detector. Data were taken as part of the ESA ALTCRISS project from late 2005 through 2007. The LET rate data shows a heavy-ion (LET>50 keV/μm) anisotropy. From the heavy-ion LET rate in the Zvezda service module we find ISS ŷ (Starboard) and ẑ (Nadir) to be about 10–15 times higher than in xˆ(Forward). The situation is similar for dose and dose equivalent rates, ranging from 25–40 μGy d⁻¹ in xˆ to about 75 μGy d⁻¹ in ẑ, whereas for the dose equivalent the rate peaks in ŷ with around 470 μSv d⁻¹. The heavy-ion anisotropy confirms what has been reported by the ALTEA collaboration. Measurements using two sets of passive detectors, DLR-TLDs and PADLES (TLD+CR-39), have also been performed in conjunction with Alteino measurements, both shielded and unshielded. The passive detectors register a dose rate about 3–5 times as high as Alteino, 260–280 μGy d⁻¹ for PADLES and 200–260 μGy d⁻¹ for DLR-TLDs. For the dose equivalent PADLES measurements ranges from 560–740 μSv d⁻¹.
No preview · Article · Jan 2014 · Journal of Physics G Nuclear and Particle Physics
[Show abstract][Hide abstract] ABSTRACT: Purpose:
In a previous paper, we showed that chemiluminescence from radical recombination (initiated by lipid peroxidation and propagated by polyunsaturated fatty acids [PUFA]) has a bleaching effect comparable to that caused by light on the rhodopsin of retinal rod outer segment (RdOS) prepared from bovine eyes. Photons generated by radical recombination were suggested to be the origin of phosphenes perceived as light flashes by the human eye. Irradiation with (12)C carbon ions was used in this study to stimulate radical production, propagation and recombination leading to photoluminescence.
Materials and methods:
(12)C radiation bleached RdOS rhodopsin, but structural damage increasing with the radiation dose was also observed. For this reason, only the effects on rhodopsin at doses producing next to negligible biodamage and permitting regeneration have been considered as bleaching effects.
(12)C irradiation bleached RdOS rhodopsin, but increasing structural damage with radiation dose was also observed. For the measure of bleaching and to reveal dose response effects on rhodopsin that were able to be regenerated only results from doses producing nearly negligible biodamage have been considered.
Recombination of radicals appears responsible for the release of photons with subsequent bleaching of rhodopsin. This effect could have an important role in the generation of the anomalous visual effects (phosphenes) experienced by patients during hadrotherapy or by astronauts in space.
Full-text · Article · May 2013 · International Journal of Radiation Biology
[Show abstract][Hide abstract] ABSTRACT: Purpose:
To report the results of short-term electrophysiologic monitoring of patients undergoing (12)C therapy for the treatment of skull chordomas and chondrosarcomas unsuitable for radical surgery.
Methods and materials:
Conventional electroencephalogram (EEG) and retinal and cortical electrophysiologic responses to contrast stimuli were recorded from 30 patients undergoing carbon ion radiation therapy, within a few hours before the first treatment and after completion of therapy. Methodologies and procedures were compliant with the guidelines of the International Federation for Clinical Neurophysiology and International Society for Clinical Electrophysiology of Vision.
At baseline, clinical signs were reported in 56.6% of subjects. Electrophysiologic test results were abnormal in 76.7% (EEG), 78.6% (cortical evoked potentials), and 92.8% (electroretinogram) of cases, without correlation with neurologic signs, tumor location, or therapy plan. Results on EEG, but not electroretinograms and cortical responses, were more often abnormal in patients with reported clinical signs. Abnormal EEG results and retinal/cortical responses improved after therapy in 40% (EEG), 62.5% (cortical potentials), and 70% (electroretinogram) of cases. Results on EEG worsened after therapy in one-third of patients whose recordings were normal at baseline.
The percentages of subjects whose EEG results improved or worsened after therapy and the improvement of retinal/cortical responses in the majority of patients are indicative of a limited or negligible (and possibly transient) acute central nervous system toxicity of carbon ion therapy, with a significant beneficial effect on the visual pathways. Research on large samples would validate electrophysiologic procedures as a possible independent test for central nervous system toxicity and allow investigation of the correlation with clinical signs; repeated testing over time after therapy would demonstrate, and may help predict, possible late toxicity.
Full-text · Article · Nov 2012 · International journal of radiation oncology, biology, physics
[Show abstract][Hide abstract] ABSTRACT: Iron abundance in cosmic rays impinging on astronauts in space habitats is of paramount importance when calculating the radiation risk for human space exploration. The concurrent high relative abundance of iron in Galactic Cosmic Rays (GCR) and iron ability to produce damages at cellular and molecular levels, together with recent radiobiology results suggests iron as a major candidate to be studied in order to produce accurate radiation hazard assessments. Iron may be in fact responsible for a large percentage of cancer risk during a long interplanetary voyage, and therefore deserves a specific attention. We built a simple model based on CREME96 for the radiation in the International Space Station (ISS) and tested it against recently performed measurements with the ALTEA and Alteino particle detectors. While we can report a good agreement between 50m and 250 keV/μm (very good for several peaks such as Si, Mg, S) we show an overestimation by this model of iron abundances of about 25–80% when compared to the measurements. New analysis on previously published work, supporting this result, are also reported.Reasons for this overestimation are discussed, they are likely to be related to the not detailed enough transport through the multiplicity of the ISS shielding and to the often used simplification of “aluminum equivalent shielding”. The iron sources in LEO, possibly not yet accurate enough when transported in Low Earth Orbit, can also play a role. New concurrent measurements (inside–outside the ISS) are suggested to help resolving this issue.
No preview · Article · Oct 2012 · Radiation Measurements
[Show abstract][Hide abstract] ABSTRACT: The knowledge of the composition of the radiation environment is an
important information for all the radiation safety issues needed for the
planning of future long manned space missions. The ALTEA detector is on
board the International Space Station since July 2006 and during this
period it has performed a detailed measurement of the radiation
environment. In this paper we present a summary of past measures and
No preview · Article · Oct 2012 · Journal of Physics Conference Series
[Show abstract][Hide abstract] ABSTRACT: Active detectors used as radiation monitors in space are not usually able to perform Particle Identification (PID). Common techniques need energy loss spectra with high statistics to estimate ion abundances. The ALTEA-space detector system is a set of silicon strip particle telescopes monitoring the radiation environment on board the International Space Station since July 2006 with real-time telemetry capabilities. Its large geometrical factor due to the concurrent use of six detectors permits the acquisition of good energy loss spectra even in a short period of observation. In this paper we present a novel Fast Probabilistic Particle Identification (FPPI) algorithm developed for the ALTEA data analysis in order to perform nuclear identification with low statistics and, with some limitations, also in real time.
No preview · Article · Aug 2012 · Advances in Space Research
[Show abstract][Hide abstract] ABSTRACT: In general, radiation exposure represents one of the greatest risks to
humans traveling on exploration missions beyond low Earth orbit (LEO).
The ALTEA detector (ALTEA-Shield experiment) is used to measure the
radiation environment in different places of the ISS-USLab. ALTEA-Shield
is part of the ALTEA program, a multidisciplinary research project which
aims at obtaining a better understanding of the radiation environment on
board the International Space Station, and also at studying the
interaction between cosmic rays and the astronauts visual system. The
ALTEA-Shield/Survey experiment, financed by the Italian Space Agency
(ASI) and sponsored by ESA, uses the six particle detectors (SDUs,
Silicon Detector Units) of ALTEA arranged on a 3D isotropic support. It
is capable to measure cosmic ray particles coming from three different
directions, being able to give an overview on the particle fluxes (in a
detectable energy range between 3 and 900 keV/um) in different locations
of the USLab. The ALTEA-Shield/Survey experiment started on September
2010 and it was placed in four locations of the USLab, resulting in a
total observation time of more than 290 days. We present here the
particle fluxes in the four positions, together with previous
measurements acquired under the ALTEA-DOSI experimental sessions in
2006-2009; ALTEA is able to discriminate ion species (charge Z) from
Z>4 and to measure the trajectory of each particle, so to be able to
reconstruct the radiation flux in the three direction XYZ. The
differences in the flux measured along these directions (along the ISS
main body and two transverse directions) are mostly due to the different
amount and quality of shielding materials passed by the incoming nuclei.
[Show abstract][Hide abstract] ABSTRACT: Rod outer segments of photoreceptors are characterized by rhodopsin, a membrane protein surrounded by phospholipids containing a very high concentration of polyunsaturated fatty acids. These fatty acids can propagate free radicals, initiated by peroxidation, whose recombination is eventually associated with light emission as chemiluminescence. The results reported here indicate that this effect produces an isomerization of the retinal (bleaching effect) of the rhodopsin, similar to that induced by light in normal vision. In vitro experiments on detergent-suspended rod outer segments (RdOS) from bovine eyes, using an enzymatic source of radicals, xanthine/xanthine oxidase, were carried out. The results indicate that the proposed mechanism is likely, because they can show the bleaching of rhodopsin in RdOS, owing to its extraordinary sensitivity. Thus this mechanism is, also, a possible explanation for anomalous visual effects such as light flashes (phosphene-like) perceived by humans. The functionality of the rhodopsin in the RdOS was first tested by visible light. Rhodopsin reactivation after bleaching was obtained by adding cis-retinal to the suspension, demonstrating the reversibility of the bleaching process. A special experimental system was developed to observe the bleaching from luminescence by radical recombination, avoiding physical contact between the rod outer segment suspension and the radicals to prevent radical-induced damage and modifications of the delicate structure of the rod outer segment.
No preview · Article · May 2012 · Free Radical Biology and Medicine
[Show abstract][Hide abstract] ABSTRACT: Solar Particle Events (SPEs) are a major concern during prolonged space missions. During such events, a large amount of light ions, mostly protons and helium nuclei, are accelerated with enough energy to traverse the spacecraft hull and therefore represent a high hazard for the crews' health. The ALTEA particle telescope was collecting continuous data inside the USLab module of the International Space Station (ISS) during most of the December 2006 SPEs. The telescope is able to measure protons and helium respectively in the 42–45 MeV and 42–250 MeV/nucleon energy ranges, heavier ions up to relativistic molybdenum, and to discriminate nuclei for Z ≥ 5. First measurements of the charged radiation environment inside the USLab during a SPE are presented. The data averaged over the entire SPE week show an increase of the light ion rate (about a factor 1.5 in the energy range of the detector) when compared to quiet Sun conditions. The increase becomes much higher during the SPE climax (13 December) reaching a factor 10 (when averaged over three ISS orbits showing the highest activity). The extension of these results beyond the detector range is discussed. Conversely, the rates of ions with Z ≥ 5 are shown not to change significantly during the SPE week.
Full-text · Article · Jul 2011 · Journal of Physics G Nuclear and Particle Physics
[Show abstract][Hide abstract] ABSTRACT: The uneven shielding of the International Space Station from the vessel hull, racks and experiments produces a modulation of the internal radiation environment. A detailed knowledge of this environment, and therefore of the Station's shielding effectiveness, is mandatory for an accurate assessment of radiation risk. We present here the first 3D measurements of the Station's radiation environment, discriminating particle trajectories and LET, made possible using the detection capability of the ALTEA-space detector. We provide evidence for a strong (factor ≈ 3) anisotropy in the inner integral LET for high-LET particles (LET > 50 keV/µm) showing a minimum along the longitudinal station axis (most shielded) and a maximum normal to it. Integrating over all measured LETs, the anisotropy is strongly reduced, showing that unstopped light ions plus the fragments produced by heavier ions approximately maintain flux/LET isotropy. This suggests that, while changing the quality of radiation, the extra shielding along the station main axis is not producing a benefit in terms of total LET. These features should be taken into account (1) when measuring radiation with detectors that cannot distinguish the direction of the impinging radiation or that are unidirectional, (2) when planning radiation biology experiments on the ISS, and (3) when simulating the space radiation environment for experiments on the ground. A novel analysis technique that fully exploits the ability to retrieve the angular distribution of the radiation is also presented as well as the angular particle flux and LET characteristic of three geomagnetic zones measured during 2009 by the ALTEA-space detector. This technique is applied to the ALTEA-space detector, but a wider applicability to other detectors is suggested.
No preview · Article · May 2011 · Radiation Research