Anomalous Long Term Effects in Astronauts' Central Nervous System (ALTEA) integrates several diagnostic technologies to measure the effect of the exposure of crewmembers to cosmic radiation. It will improve the understanding of the impacts that radiation has on the human central nervous system functions, and will study the flashes from cosmic radiation that astronauts have reported since the Apollo flights. ALTEA will also provide an assessment of the radiation environment in the ISS.Principal Investigator(s)
Italian Space Agency (ASI), Rome, , Italy
Alenia Spazio - Laben, Milano, , Italy
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Italian Space Agency (ASI)Research Benefits
Information PendingISS Expedition Duration:
April 2006 - October 2007Expeditions Assigned
13,14,15Previous ISS Missions
The predecessor of ALTEA, Alteino, was conducted aboard ISS in April of 2002 during a Soyuz taxi mission.
Long-duration space flights result in increased cosmic radiation exposure to astronauts. The ALTEA hardware is
designed to measure particle radiation in the space environment, and determine how this radiation impacts the
central nervous system (CNS) of the crew. The experiment is comprised of a helmet-shaped device holding 6
silicon particle detectors designed to measure cosmic radiation passing through the brain. The detectors measure the
trajectory, energy, and species of individual ionizing particles. At the same time an electroencephalograph (EEG)
will measure the brain activity of the crewmember to determine if radiation strikes cause changes in the
electrophysiology of the brain in real time.
A common effect of radiation exposure that is reported by astronauts is the perception of light flashes. The actual mechanism of these light flashes is not understood. Earlier studies on the Mir space station suggest that both heavy nuclei and protons trigger abnormal CNS responses. (Casolino et al, 2003). A Visual Stimulator tests the astronaut's overall visual system, including dark adaptation stimuli to monitor visual status. . While not manned, the ALTEA hardware provides a continuous measure of the cosmic radiation in the ISS U.S. Laboratory, Destiny. The neurophysiological effects of cosmic radiation in long term space travel have never been explored with the depth of the ALTEA experiment. Data collected will help quantify risks to astronauts on future long-duration space missions and propose optimized countermeasures.
Astronauts from Apollo missions onward have reported seeing unexplained light flashes (phosphenes), which were attributed to abnormal brain function caused by space radiation. Outside the protection of Earth's magnetic shield, ISS crewmembers are exposed to increased radiation, but the radiation environment is even more severe as exploration crews leave Earth's geomagnetic field and transit to other planets. The tests conducted using the ALTEA hardware will help scientists characterize how the heavy ion radiation of space impacts the brain and whether or not that radiation causes any temporary or permanent abnormalities in the brain function and the visual system in particular.Earth Applications
Data provided from ALTEA can lead to further understanding of how radiation may affect brain function on Earth as well as in space. While the levels of heavy ion radiation are much higher in space that on Earth, any understanding into the way radiation may alter brain function is extremely useful to neuroscientists of these studies. Ion therapies to treat brain tumors will also benefit from the ALTEA results.
Once the crewmember being tested has set up the experiment he or she then wears the ALTEA helmet for roughly 90 minutes, the time it takes for the ISS to completely orbit the Earth. ALTEA will require 6 of these tests.Operational Protocols
A typical manned run of the experiment involves setting up the ALTEA hardware and performing calibrations before the ALTEA helmet is donned by the crewmember. The crewmember will then wear the helmet for 90 minutes while the sensors in the helmet are collecting EEG measurement. The unmanned run does not require crewtime after it is launched.
Since the Apollo flights to the Moon, it has been known that most astronauts experience sudden visual light flashes during space flight. Described in early reports as occurring in darkness and typically before falling asleep, these light flashes are thought to originate as an effect of high-energy particles, abundant in space, interacting with the eye and/or the visual anatomy.
The ALTEA (Anomalous Long Term Effects on Astronauts) project, active on ISS since August 2006, currently investigating the ISS-US Lab radiation environment (ALTEA-DOSI, ALTEA-SHIELD/survey), has also been studying the risks of possible damage to the brain from particle radiation in space (ALTEA-CNSM). It is proposed that these interaction effects may go well beyond light flashes and could constitute a new kind of risk for longer space voyages. One study focus was on these abnormal visual perceptions and the impact on retinal and brain visual structures. ALTEA, with its six double detectors covering most of the astronaut?s head, permits a 3-D reconstruction of the energy released in the brain by ionizing particles. In addition, ALTEA monitors the functional state of the optical pathway in order to interpret the biophysical mechanisms generating abnormal perceptions (Narici et al., 2004).
In the framework of ALTEA, a survey was conducted in 2003 with 59 astronauts on the perception of light flashes, or "phosphenes", during missions. It was found that 80% of space explorers experience light flashes at some point (mainly before sleep when the eyes are night adjusted). As many as 20% of the respondents thought that light flashes sometimes disturbed their sleep. Light flashes are predominantly white, but other colors are mentioned, in particular yellow (10%). Most light flashes have an elongated shape, like stripes or comets, and are associated with a perception of motion. The motion is left-right or in-out, but never up-down, and about 8% of light flashes have a "blob" shape. There is a positive correlation between light flashes and radiation flux, and the majority of light flash in space is most likely produced by a direct interaction of an ion with the retina, although there is indirect indication that light flashes can result from interaction between particles and brain structures as well (Fuglesang et al., 2006).
ALTEA's predecessor, Alteino/SilEye3, provided the first measurement with particle nuclear identification of the radiation environment in the ISS, and gave the research team the opportunity to master electroencephalogram (EEG) measurements in space. Seven ALTEA-CNSM (Central Nervous System Monitoring) sessions with 3 astronauts have been performed to date with the last session lengthened for a full passage through the South Atlantic Anomaly (SAA). The seven sessions produced 20 perceived light flashes in about 7 hours of observation. More than half of these light flashes were recorded in a single session. The astronaut performing the last session paid particular attention during the SAA transit, however, reported no light flash during that period. Using the discriminating and tracking capability of ALTEA, the ionizing radiation passing through the eyes and brain of the astronauts has been measured and characterized for the first time. The total rate of radiation passing through the head in the energy range detected by ALTEA were evaluated and consistently yielded 20 ions per minute in the eyes and 400?500 ions per minute for the brain. Geometrical considerations show that only about 1 particle will be measured for every 6?7 passing through the eye. Indeed researchers identified 3 specific ion candidates for the 20 light flashes. Preliminary findings seem to indicate that the most probable ions for generating these flashes were light ions. Further data analysis should permit the contributions of the different ions to be separated and the dose per day in the eye/brain to be determined. Head radiation exposure is then quantified and, in principle, be applicable to any ISS orbits (excluding SAA), and to any crewmember.
The large variability of the light flash reports from the astronauts is unlikely to be explained entirely by differences in radiation kind and amount (due to altitude, latitude and vessel shielding), thus giving hints toward the coexistence of other routes to light flash generation. And according to investigators, physiological and psychological factors should be included as well. This should be taken into account when interpreting the, lower than expected, light flash rate measured by ALTEA, which might be only partly explained by the better shielding of the ISS Destiny Lab and by the possible non complete dark adaption as suggested by one of the subjects. The study of the radiation environment in the ISS along with crewmembers' electrophysiological measurements will provide more complete risk assessment and for countermeasure strategies to be developed. Finally these findings may be extrapolated for future interplanetary missions, the next return to the Moon, or flight to Mars (Narici 2008).
Taking the US Lab hull thickness as an adjustable parameter, the ALTEA team found that 5 centimeters represents the best value for the real thickness transverse by the outer radiation particles when entering the space station structure in location Lab1P1, on the port side close to Node 2. A survey of several location in the US Lab is planned for the continuation of the ALTEA experiment (ALTEA-Shield). This experiment will allow researchers to estimate, among other quantities, the shielding thickness at different locations thus giving data to calculate the average shielding thickness of the USLab (La Tessa et al., 2009).
The 2006?2007 radiation measurements which spanned for a total of about 11 months for three regions (polar, equatorial and South Atlantic Anomaly) revealed that the spectra of the radiation after being transported inside the ISS reflect the differences due to the varying energy cutoff in a similar way for all the ion peaks, consequently the relative abundances are not significantly different from the ones calculated with the data from all regions. Researchers also found that the cosmic ray relative nuclear abundances do not change considerably between the outside and the inside of the ISS. The small differences observed can be accounted for by the nuclear interactions of the ions with the ISS hull. The Fe abundance, about one-half of the previously published value, has not been completely understood and its meaning is currently under investigation. The ion transport mechanism through aluminum and the cross-sections of the nuclear reactions that cosmic rays experience crossing matter are being studied to explain the ALTEA abundance values. The results from these investigations will be reported in the future. (Zaconte et al., 2010).
Solar Particle Events (SPEs) could represent a high radiation hazard for ISS crew. During most of the December 2006 SPE, the ALTEA detector collected continuous data inside the US Lab module. 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). As expected, the SPE produces an increase of the light ion (Z < 5) rate with respect to the values recorded during the quiescent times. At the same time, the rates of heavier ions with Z > 5 did not change significantly. Nevertheless, these results indicate that a SPE significantly affects radiation Linear Energy Transfer (LET) in the ISS, producing a substantial increase of low-LET radiation rate which reaches the highest values in quite short periods, confirming the need to consider SPEs in those biological processes for which radiation rate plays an important role. These results provide the first information for charged radiation risk assessment in space habitats during a SPE (Larosa et al., 2011).
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