International Space Station Missions Research Articles

Influence of microgravity on spontaneous calcium activity of primary hippocampal neurons grown in microfluidic chips

The influence of variations of gravity, either hypergravity or microgravity, on the brain of astronauts is a major concern for long journeys in space, to the Moon or to Mars, or simply long-duration missions on the ISS (International Space Station). Monitoring brain activity, before and after ISS missions already demonstrated important and long term effects on the brains of astronauts. In this study, we focus on the influence of gravity variations at the cellular level on primary hippocampal neurons. A dedicated setup has been designed and built to perform live calcium imaging during parabolic flights. During a CNES (Centre National d’Etudes Spatiales) parabolic flight campaign, we were able to observe and monitor the calcium activity of 2D networks of neurons inside microfluidic devices during gravity changes over different parabolas. Our preliminary results clearly indicate a modification of the calcium activity associated to variations of gravity.

Ocular complaints and diagnoses in spaceflight.

The NASA human system risk board (HSRB) has long focused on trauma and acute medical illness as a key contributor to high level in-flight medical risk. However, ocular issues, trauma, and complaints during spaceflight are poorly characterized. In a retrospective case series, the NASA data from the life sciences data archieve (LSDA) and the lifetime surveillance of astronaught health (LSAH) was queried for eye related complaints and conditions in spaceflight across international space station (ISS) missions and space shuttle (STS) missions. The ISS dataset included missions from the year 2000 to 2020, and the STS dataset included missions from 1981 to 2011. Data were reviewed and segmented into categories of ocular complaints. 135 STS missions and 63 ISS missions were included in this analysis. Ocular events were only noted across 83 STS missions (61.5%) and 41 ISS missions (65.1%). Overall, the most common ocular complaints were eye irritation (n = 80, 33.1%), ocular foreign body or foreign body sensation (n = 55, 22.7%), dry eye syndromes (n = 38, 15.7%), epiphora or excessive tearing (n = 19, 7.85%). Of all ocular complaints or diagnoses, 9 (3.72%) were considered higher severity (keratitis, corneal ulcer, chemical exposure, and corneal abrasion). However, seemingly none required evacuation from mission. Improved depiction of ocular symptoms and diagnoses, and a more standard classification system and process to describe ocular symptoms, diagnoses, and treatments in space is crucial to provide more effective and comprehensive treatments.

Neurocognitive Adaptations for Spatial Orientation and Navigation in Astronauts.

Astronauts often face orientation challenges while on orbit, which can lead to operator errors in demanding spatial tasks. In this study, we investigated the impact of long-duration spaceflight on the neural processes supporting astronauts' spatial orientation skills. Using functional magnetic resonance imaging (fMRI), we collected data from 16 astronauts six months before and two weeks after their International Space Station (ISS) missions while performing a spatial orientation task that requires generating a mental representation of one's surroundings. During this task, astronauts exhibited a general reduction in neural activity evoked from spatial-processing brain regions after spaceflight. The neural activity evoked in the precuneus was most saliently reduced following spaceflight, along with less powerful effects observed in the angular gyrus and retrosplenial regions of the brain. Importantly, the reduction in precuneus activity we identified was not accounted for by changes in behavioral performance or changes in grey matter concentration. These findings overall show less engagement of explicitly spatial neurological processes at postflight, suggesting astronauts make use of complementary strategies to perform some spatial tasks as an adaptation to spaceflight. These preliminary findings highlight the need for developing countermeasures or procedures that minimize the detrimental effects of spaceflight on spatial cognition, especially in light of planned long-distance future missions.

Optic disc edema during strict 6° head-down tilt bed rest is related to one-carbon metabolism pathway genetics and optic cup volume

Some astronauts on International Space Station missions experience neuroophthalmological pathologies as part of spaceflight associated neuro-ocular syndrome (SANS). Strict head-down tilt bed rest (HDTBR) is a spaceflight analog that replicates SANS findings and those who had 3–4 risk alleles (G and C alleles from the methionine synthase reductase [MTRR] A66G and serine hydroxymethyltransferase [SHMT1] C1420T, respectively) as compared to 1-2 risk alleles, had a greater increase in total retinal thickness (TRT). The objective of this study was to identify factors that contribute to the individual variability of the development of SANS in a 60 d HDTBR at the German Aerospace Center’s:envihab facility, Cologne Germany. 22 of 24 subjects who participated in the HDTBR study provided blood samples for genetic analysis. Total retinal thickness and optic cup volume were measured before and after bed rest. Subjects with 3–4 versus 0-2 risk alleles had greater ΔTRT during and after bed rest, and the model improved with the addition of baseline optic cup volume. This bed rest study confirms that variants of MTRR and SHMT1 are associated with ocular pathologies. Subjects with more risk alleles had the greatest HDTBR-induced ΔTRT, reaffirming that genetics predispose some individuals to developing SANS. Preflight optic cup volume and genetics better predict ΔTRT than either one alone. Whether nutritional supplements can override the genetic influences on biochemistry, physiology, and pathophysiology remains to be tested. These findings have significant implications for both aerospace and terrestrial medicine.

Designing Visual Displays for Deep Space Habitats: Challenges and Opportunities from a Cognitive Task Analysis with ISS Mission Control

This paper explores some challenges and opportunities in designing visual interfaces for deep space habitats with communication delays to Earth. The study first examines how Mission Control for the International Space Station (ISS) operates in detecting and responding to anomalous events. Interviews with participants who have held roles as flight controllers, backroom engineers, astronauts, or flight instructors for ISS and shuttle missions were conducted to gain insights into the responses to anomalous events. The collected anomalous scenarios were then re-considered under the context of deep space missions, where communication delays and other environmental factors are substantially different. Findings and insights on data analysis of the anomalous scenarios were then presented subsequently. Based on the findings, four areas of challenges and opportunities for visual interfaces design were identified. The paper suggests that these design challenges and opportunities be considered in more detail in future research.

Non-targeted effects and space radiation risks for astronauts on multiple International Space Station and lunar missions

Future space travel to the earth's moon or the planet Mars will likely lead to the selection of experienced International Space Station (ISS) or lunar crew persons for subsequent lunar or mars missions. Major concerns for space travel are galactic cosmic ray (GCR) risks of cancer and circulatory diseases. However large uncertainties in risk prediction occur due to the quantitative and qualitative differences in heavy ion microscopic energy deposition leading to differences in biological effects compared to low LET radiation. In addition, there are sparse radiobiology data and absence of epidemiology data for heavy ions and other high LET radiation. Non-targeted effects (NTEs) are found in radiobiology studies to increase the biological effectiveness of high LET radiation at low dose for cancer related endpoints. In this paper the most recent version of the NASA Space Cancer Risk model (NSCR-2022) is used to predict mission risks while considering NTEs in solid cancer risk predictions. I discuss predictions of space radiation risks of cancer and circulatory disease mortality for US Whites and US Asian-Pacific Islander (API) populations for 6-month ISS, 80-day lunar missions, and combined ISS-lunar mission. Model predictions suggest NTE increase cancer risks by about ∼2.3 fold over a model that ignores NTEs. US API are predicted to have a lower cancer risks of about 30% compared to US Whites. Cancer risks are slightly less than additive for multiple missions, which is due to the decease of risk with age of exposure and the increased competition with background risks as radiation risks increase. The inclusion of circulatory risks increases mortality estimates about 25% and 37% for females and males, respectively in the model ignoring NTEs, and 20% and 30% when NTEs are assumed to modify solid cancer risk. The predictions made here for combined ISS and lunar missions suggest risks are within risk limit recommendations by the National Council on Radiation Protection and Measurements (NCRP) for such missions.

Databases of the evolution of the microbiome and its drug susceptibility in astronauts and hermetic facility operators

When planning lunar bases and during long-term interplanetary (autonomous) flights, the issue of accumulation of pathogenic microbiota in conditions of closed inhabited objects is relevant. This question can be answered on the basis of a long observation period. When conducting microbiological examinations on the International Space Station, it was shown that one of the main features of the human-microorganisms ecological system in the environment of manned spacecraft is the periodic accumulation of the pathogenicity potential of microorganisms. These results were confirmed in isolation ground experiments and in the analysis of the SALYUT-6, 7 and MIR, International Space Station missions. Our work presents databases of microbiota and its antibiotic resistance of cosmonauts and hermetic facility operators at various stages of space flight, or isolation experiments. The databases are designed to assess the evolution of the population of microorganisms and their antibiotic resistance in various parts of the body of cosmonauts and operators of hermetic objects before, during and after a space flight and isolation experiments. Information about the microbiome of astronauts has been streamlined and entered into the database since 1970. The databases contain information about the microbiota in chronological order and its antibiotic resistance in cosmonauts and pressurized facility operators. Samples of various parts of the body were analyzed: forehead, chest, neck, ear, arm, armpit, groin, intestines, plaque, oral cavity, pharynx, tongue, nose, cheeks. Experimental samples of microbiota obtained from the International Space Station are stored at a deep freeze of -76 °С, are examined using a standard bacteriological method, molecular biology research methods and immunochemical methods. The information obtained makes it possible to assess the normal and dysbiotic state of the cosmonauts' microbiota. The databases are constantly updated. Thanks to the adapted database format, it is possible to use neural network and BIG DATA methods for analysis.

СОПОСТАВЛЕНИЕ С НОРМАМИ РАДИАЦИОННОЙ БЕЗОПАСНОСТИ УРОВНЕЙ ДОЗ НА КРИТИЧЕСКИЕ ОРГАНЫ ТЕЛА ЧЕЛОВЕКА ПРИ ДЛИТЕЛЬНЫХ ПОЛЕТАХ НА ОРБИТАЛЬНЫХ СТАНЦИЯХ «МИР» И МКС

We analyzed the averaged through the year power of local tissue absorbed doses measured by the standard instruments over 15 years of station Mir operation (28 missions) and analogous data over 22 years of the International space station (ISS) operation (67 missions) within solar cycles (SCs) 22–25. This is a huge set of daily measurements of dosimeters R-16 (ioinization chamber D2) and 4 semiconductor dosimeters DB-8, located in different compartments. We also present the experimental and calculated absorbed and equivalent doses to the skin, lens and hematopoietic system (HPS) received within a day and year in space. It was found that in all Mir and ISS missions the equivalent doses to these tissues were below the limits adopted for orbital missions. In many missions of 6 to 8 months, the effective and equivalent doses to the CNS, lens and skin did not exceed even the lower dose limits prescribed by Russian radiation safety standard NRB-99/2009 for nuclear industry. Maximal equivalent dose values to the lens and skin in a year-long mission did not exceed 404 mSv. These values are less than the existing limits for space missions by 32 % for the lens and 5 times for the skin.

Meta-analysis of health research data from greater than three months International Space Station missions

Despite extensive research, the understanding of human health changes that result from long-duration spaceflight remains limited, in part due to the wide range of study types and designs, lack of independent experiment replication and data dispersal in many articles. We have compiled a database from 37 health studies that reported data for 517 parameters from missions of longer than 3-month duration on the International Space Station. We found an abundance of physiological and biochemical parameters and limited psychological/behavioral in-flight data. When we compared in-flight to pre-flight data, 14 out of 40 studied measurement type categories changed significantly, whereas only 3 categories changed significantly post-flight. Collagen breakdown biomarkers in urine showed the greatest effect, a 2-fold increase in-flight, but no data in this category was reported post-flight. Eye movements related to the vestibular system function had the greatest in-flight effect that was sustained post-flight, with a decrease of 81% in-flight and a 32% decrease remained post-flight. Analysis of the in-flight compared to post-flight biochemical and physiological changes revealed overall low correlations (R2 = 0.03 & R2 = 0.23, respectively), as parameters tend to return to baseline post-flight. As we look to longer duration space missions, this review provides an opportunity to identify and highlight salient results that have been reported to date for long duration spaceflight, to enhance our understanding of space health and to develop effective countermeasures. We believe that the compiled data could be explored for medical interpretation of the observed changes, in-flight timeline of changes for natural history studies, correlation analysis for parameters across different body systems, and comparison of in-flight responses to ground-based studies.

Multiple field tests on landing day: Early mobility may improve postural recovery following spaceflight.

Adaptation to microgravity causes astronauts to experience sensorimotor disturbances during return to Earth leading to functional difficulties. Recently, the Field Test (FT) study involving an incrementally demanding sensorimotor functional test battery has allowed for an unprecedented view into early decrements and recovery from multiple tests conducted on the landing day following 6-months International Space Station missions. Although the protocol was challenging and temporarily increased motion sickness symptoms, there were anecdotal reports that performing these tasks within the first few hours of landing accelerated their recovery. Therefore, results from computerized dynamic posturography (CDP) following return to Houston were used to compare recovery between crewmembers that participated in FT (n = 18) with those that did not (controls, n = 11). While there were significant decrements in postural performance for both groups, some FT participants tended to perform closer to their preflight baseline in the most challenging condition of the CDP sensitive to vestibular function—eyes closed, unstable support and head movements. However, the distribution of difference scores appeared bimodal with other FT participants in the lower range of performance. We attribute these observations to the manner in which the field tests were implemented—some benefitted by encouraging early movement to drive adaptation when performed in a constrained incremental fashion; however, movements above aversive thresholds may have impaired adaptation in others. Challenging the sensorimotor system with increasingly provocative movements performed as close to landing as possible, as long as within individual thresholds, could be a useful intervention to accelerate astronaut’s sensorimotor readaptation that deserves further study.

Similar Loss of Executive Function Performance after Exposure to Low (10 cGy) Doses of Single (4He) Ions and the Multi-Ion GCRSim Beam.

While astronauts are trained to deal with multiple issues that they are likely to encounter during a mission, it is likely that some problems will arise that astronauts have no direct experience in resolving. During International Space Station (ISS) missions, astronauts can rely on Mission Control to help resolve complex problems, however during the long-duration space missions planned to the Moon and Mars, astronauts will have to act more autonomously, thus the ability of astronauts to conduct executive function will be critical for problem solving during deep space missions. Several studies have shown that exposure to space radiation results in decreased executive function performance. However, to date these studies have used single ions, whereas there is a complex mixture of ion species and energies within the space-radiation spectrum that astronauts will be exposed to. Thus, there is some concern that the neurocognitive impairments reported from single ion studies will not be representative of the severity, frequency or nature of cognitive deficits that arise following exposure to more complex space-radiation spectra. The current study has determined the relative impact that isodoses of He ions or the simplified 6-ion-galactic cosmic ray simulation (GCRSim) beams had on the performance of male Wistar rats in executive function tasks, attentional set shifting (ATSET) task and unconstrained cognitive flexibility (UCFlex). Exposure to 10 cGy GCRSim induced performance deficits in the simple discrimination (SD) stage of the ATSET task, which appears to be universally impacted by all space-radiation ions studied to date. The magnitude of the SD performance decrements in the GCRSim-irradiated rats were comparable to those observed in He-irradiated rats. Importantly, space-radiation exposure does not appear to decrease the ability of rats to identify the key cues in the ATSET task, but increased the time/number of iterations required to successfully find the solution. Practice effect (PE) analysis (comparing prescreen to the postirradiation SD performance) revealed that while the sham-treated rats completed the second ATSET task in 30% less time than they did the prescreen ATSET test (despite the perceptual domain of the relevant (rewarded) cue being changed), the space-radiation-exposed rats took 50% longer to do so. The space-radiation-induced delay in problem solving was not confined to the ATSET task, but was also observed when rats were screened for UCFlex performance. Should similar changes occur in astronauts, these data raise the possibility that space-radiation exposure would reduce in-flight improvement in performance in repetitive tasks (PE) and may lead to a reduced ability to utilize transitive inference from "similar" problems to solve issues that have not been previously encountered.

Similar Loss of Executive Function Performance after Exposure to Low (10 cGy) Doses of Single (4He) Ions and the Multi-Ion GCRSim Beam.

While astronauts are trained to deal with multiple issues that they are likely to encounter during a mission, it is likely that some problems will arise that astronauts have no direct experience in resolving. During International Space Station (ISS) missions, astronauts can rely on Mission Control to help resolve complex problems, however during the long-duration space missions planned to the Moon and Mars, astronauts will have to act more autonomously, thus the ability of astronauts to conduct executive function will be critical for problem solving during deep space missions. Several studies have shown that exposure to space radiation results in decreased executive function performance. However, to date these studies have used single ions, whereas there is a complex mixture of ion species and energies within the space-radiation spectrum that astronauts will be exposed to. Thus, there is some concern that the neurocognitive impairments reported from single ion studies will not be representative of the severity, frequency or nature of cognitive deficits that arise following exposure to more complex space-radiation spectra. The current study has determined the relative impact that isodoses of He ions or the simplified 6-ion-galactic cosmic ray simulation (GCRSim) beams had on the performance of male Wistar rats in executive function tasks, attentional set shifting (ATSET) task and unconstrained cognitive flexibility (UCFlex). Exposure to 10 cGy GCRSim induced performance deficits in the simple discrimination (SD) stage of the ATSET task, which appears to be universally impacted by all space-radiation ions studied to date. The magnitude of the SD performance decrements in the GCRSim-irradiated rats were comparable to those observed in He-irradiated rats. Importantly, space-radiation exposure does not appear to decrease the ability of rats to identify the key cues in the ATSET task, but increased the time/number of iterations required to successfully find the solution. Practice effect (PE) analysis (comparing prescreen to the postirradiation SD performance) revealed that while the sham-treated rats completed the second ATSET task in 30% less time than they did the prescreen ATSET test (despite the perceptual domain of the relevant (rewarded) cue being changed), the space-radiation-exposed rats took 50% longer to do so. The space-radiation-induced delay in problem solving was not confined to the ATSET task, but was also observed when rats were screened for UCFlex performance. Should similar changes occur in astronauts, these data raise the possibility that space-radiation exposure would reduce in-flight improvement in performance in repetitive tasks (PE) and may lead to a reduced ability to utilize transitive inference from "similar" problems to solve issues that have not been previously encountered.

Effects of Long-duration Microgravity and Gravitational Transitions on Fine Motor Skills.

Assess the effects of long-duration microgravity and gravitational transitions on fine motor skills using a tablet-based test battery of four fine motor tasks: Pointing, Dragging, Shape Tracing, and Pinch-Rotate. While there have been some studies on fine motor skills in microgravity, few have measured the fine motor skills that are core components of interaction with computer-based devices, and none have measured performance systematically, to include preflight, inflight, and postflight space mission time periods. Seven astronauts completed the Fine Motor Skills test battery 30-40 times before, during, and up to 30 days after standard duration International Space Station missions, while a matching set of seven ground-based control participants also completed the battery over a comparable period of time. Response time and accuracy were the primary outcome measures. Relative to controls, astronauts experienced fine motor skill decrements at gravitational transitions (first week on orbit, and first month post landing). No decrements were found inflight after the first week of adaptation. Gravitational transitions appear to negatively impact fine motor skills needed to operate small controls with accuracy, such as those on touchscreen interfaces. This raises concerns for future long-duration crewmembers who will land on a planetary surface and need to perform critical tasks accurately, such as configuring spacesuits, powering up a habitat, or teleoperating rovers. Results from this study highlight the need for confirmatory research, and the possible need for countermeasure development. The Fine Motor Skills test battery may have application outside of NASA as a fine motor skills diagnostic screening, rehabilitation, or readiness-to-perform tool.

Microgravity crystallization of perdeuterated tryptophan synthase for neutron diffraction

Biologically active vitamin B6-derivative pyridoxal 5′-phosphate (PLP) is an essential cofactor in amino acid metabolic pathways. PLP-dependent enzymes catalyze a multitude of chemical reactions but, how reaction diversity of PLP-dependent enzymes is achieved is still not well understood. Such comprehension requires atomic-level structural studies of PLP-dependent enzymes. Neutron diffraction affords the ability to directly observe hydrogen positions and therefore assign protonation states to the PLP cofactor and key active site residues. The low fluxes of neutron beamlines require large crystals (≥0.5 mm3). Tryptophan synthase (TS), a Fold Type II PLP-dependent enzyme, crystallizes in unit gravity with inclusions and high mosaicity, resulting in poor diffraction. Microgravity offers the opportunity to grow large, well-ordered crystals by reducing gravity-driven convection currents that impede crystal growth. We developed the Toledo Crystallization Box (TCB), a membrane-barrier capillary-dialysis device, to grow neutron diffraction-quality crystals of perdeuterated TS in microgravity. Here, we present the design of the TCB and its implementation on Center for Advancement of Science in Space (CASIS) supported International Space Station (ISS) Missions Protein Crystal Growth (PCG)-8 and PCG-15. The TCB demonstrated the ability to improve X-ray diffraction and mosaicity on PCG-8. In comparison to ground control crystals of the same size, microgravity-grown crystals from PCG-15 produced higher quality neutron diffraction data. Neutron diffraction data to a resolution of 2.1 Å has been collected using microgravity-grown perdeuterated TS crystals from PCG-15.

Operator's Reliability During Spacecraft Docking Training on Board Mir and ISS

BACKGROUND: The experimental research PILOT on board the space stations aimed to assess cosmonauts expectable reliability in a mission relevant operation, the manual docking of Soyuz or Progress spacecrafts on the space stations Mir and International Space Station (ISS), respectively.METHOD: Therefore, a simulation of the docking of two space apparatuses was used for training and research. The methodological approach is described, taking into consideration the level of performance and the individual effort spent, the psychophysiological costs. In three decades altogether 32 cosmonauts took part.RESULTS: A significant increase of reliability was found from Mir (0.45 scores) to ISS missions (0.51). On ISS the reliability remained stable (0.50 0.1).DISCUSSION: Salnitskis model for the evaluation of operators reliability was further developed and tested, which turned out to be sensitive as well as robust enough for a practical application in this critical operational task.Johannes B, Bronnikov SV, Bubeev JA, Kotrovskaya TI, Shastlivtseva DV, Piechowski S, Hoermann H-J, Jordan J. Operators reliability during spacecraft docking training on board Mir and ISS. Aerosp Med Hum Perform. 2021; 92(7):541549.

Visuomotor Adaptation Brain Changes During a Spaceflight Analog With Elevated Carbon Dioxide (CO2): A Pilot Study.

Astronauts on board the International Space Station (ISS) must adapt to several environmental challenges including microgravity, elevated carbon dioxide (CO2), and isolation while performing highly controlled movements with complex equipment. Head down tilt bed rest (HDBR) is an analog used to study spaceflight factors including body unloading and headward fluid shifts. We recently reported how HDBR with elevated CO2 (HDBR+CO2) affects visuomotor adaptation. Here we expand upon this work and examine the effects of HDBR+CO2 on brain activity during visuomotor adaptation. Eleven participants (34 ± 8 years) completed six functional MRI (fMRI) sessions pre-, during, and post-HDBR+CO2. During fMRI, participants completed a visuomotor adaptation task, divided into baseline, early, late and de-adaptation. Additionally, we compare brain activity between this NASA campaign (30-day HDBR+CO2) and a different campaign with a separate set of participants (60-day HDBR with normal atmospheric CO2 levels, n = 8; 34.25 ± 7.9 years) to characterize the specific effects of CO2. Participants were included by convenience. During early adaptation across the HDBR+CO2 intervention, participants showed decreasing activation in temporal and subcortical brain regions, followed by post- HDBR+CO2 recovery. During late adaptation, participants showed increasing activation in the right fusiform gyrus and right caudate nucleus during HDBR+CO2; this activation normalized to baseline levels after bed rest. There were no correlations between brain changes and adaptation performance changes from pre- to post HDBR+CO2. Also, there were no statistically significant differences between the HDBR+CO2 group and the HDBR controls, suggesting that changes in brain activity were due primarily to bed rest rather than elevated CO2. Five HDBR+CO2 participants presented with optic disc edema, a sign of Spaceflight Associated Neuro-ocular Syndrome (SANS). An exploratory analysis of HDBR+CO2 participants with and without signs of SANS revealed no group differences in brain activity during any phase of the adaptation task. Overall, these findings have implications for spaceflight missions and training, as ISS missions require individuals to adapt to altered sensory inputs over long periods in space. Further, this is the first study to verify the HDBR and elevated CO2 effects on the neural correlates of visuomotor adaptation.

Predicting chromosome damage in astronauts participating in international space station missions

Space radiation consists of energetic protons and other heavier ions. During the International Space Station program, chromosome aberrations in lymphocytes of astronauts have been analyzed to estimate received biological doses of space radiation. More specifically, pre-flight blood samples were exposed ex vivo to varying doses of gamma rays, while post-flight blood samples were collected shortly and several months after landing. Here, in a study of 43 crew-missions, we investigated whether individual radiosensitivity, as determined by the ex vivo dose–response of the pre-flight chromosome aberration rate (CAR), contributes to the prediction of the post-flight CAR incurred from the radiation exposure during missions. Random-effects Poisson regression was used to estimate subject-specific radiosensitivities from the preflight dose–response data, which were in turn used to predict post-flight CAR and subject-specific relative biological effectiveness (RBEs) between space radiation and gamma radiation. Covariates age, gender were also considered. Results indicate that there is predictive value in background CAR as well as radiosensitivity determined preflight for explaining individual differences in post-flight CAR over and above that which could be explained by BFO dose alone. The in vivo RBE for space radiation was estimated to be approximately 3 relative to the ex vivo dose response to gamma irradiation. In addition, pre-flight radiosensitivity tended to be higher for individuals having a higher background CAR, suggesting that individuals with greater radiosensitivity can be more sensitive to other environmental stressors encountered in daily life. We also noted that both background CAR and radiosensitivity tend to increase with age, although both are highly variable. Finally, we observed no significant difference between the observed CAR shortly after mission and at > 6 months post-mission.

Determining the deformation and resulting coupling efficiency degradation of ultrastable fiber-coupled optical benches under load.

Fiber-coupled optical benches are an integral part of many laser systems. The base of such an optical bench is usually a slab of solid material, onto which optical components are fixed. In many environments, the ability to retain high fiber coupling efficiency under mechanical loads is essential. In this article, we study the fiber-to-fiber coupling efficiency under the application of static mechanical loads experimentally and theoretically: We constructed a simple three-point bending setup to interferometrically measure the deformation of an optical bench under load. Using the same setup, we further recorded the resulting coupling efficiency variations. The examined optical benches are based on Zerodur optical benches used in sounding rockets and International Space Station missions. We also developed an analytical model that incorporates an Euler-Bernoulli beam deformation model and a simple model for calculating the coupling efficiency, to which the experimentally obtained data are compared. Furthermore, we use a finite element method simulation to compare to the recorded deformation data. Recorded data, the analytical model, and simulations show good agreement. We also show how the presented analytical model can easily be expanded to contain more complex beam paths and, thus, be used to estimate coupling losses for experimentally relevant optical benches under load.

Beyond Low-Earth Orbit: Characterizing Immune and microRNA Differentials following Simulated Deep Spaceflight Conditions in Mice.

SummarySpaceflight missions can cause immune system dysfunction in astronauts with little understanding of immune outcomes in deep space. This study assessed immune responses in mice following ground-based, simulated deep spaceflight conditions, compared with data from astronauts on International Space Station missions. For ground studies, we simulated microgravity using the hindlimb unloaded mouse model alone or in combination with acute simulated galactic cosmic rays or solar particle events irradiation. Immune profiling results revealed unique immune diversity following each experimental condition, suggesting each stressor results in distinct circulating immune responses, with clear consequences for deep spaceflight. Circulating plasma microRNA sequence analysis revealed involvement in immune system dysregulation. Furthermore, a large astronaut cohort showed elevated inflammation during low-Earth orbit missions, thereby supporting our simulated ground experiments in mice. Herein, circulating immune biomarkers are defined by distinct deep space irradiation types coupled to simulated microgravity and could be targets for future space health initiatives.

Assessment of Global Ocular Structure Following Spaceflight Using a Micro-Computed Tomography (Micro-CT) Imaging Method.

Reports show that prolonged exposure to a spaceflight environment produces morphologic and functional ophthalmic changes in astronauts during and after an International Space Station (ISS) mission. However, the underlying mechanisms of these spaceflight-induced changes are currently unknown. The purpose of the present study was to determine the impact of the spaceflight environment on ocular structures by evaluating the thickness of the mouse retina, the retinal pigment epithelium (RPE), the choroid and the sclera layer using micro-CT imaging. Ten-week-old C57BL/6 male mice were housed aboard the ISS for a 35-day mission and then returned to Earth alive for tissue analysis. For comparison, ground control (GC) mice on Earth were maintained in identical environmental conditions and hardware. Ocular tissue samples were collected for micro-CT analysis within 38(±4) hours after splashdown. The images of the cross-section of the retina, the RPE, the choroid, and the sclera layer of the fixed eye was recorded in an axial and sagittal view using a micro-CT imaging acquisition method. The micro-CT analysis showed that the cross-section areas of the retina, RPE, and choroid layer thickness were changed in spaceflight samples compared to GC, with spaceflight samples showing significantly thinner cross-sections and layers compared to controls. The findings from this study indicate that micro-CT evaluation is a sensitive and reliable method to characterize ocular structure changes. These results are expected to improve the understanding of the impact of environmental stress on global ocular structures.