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All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Comparisons of Integrated Radiation Transport Models with Microdosimetry Data in Spaceflight

Astronauts are exposed to galactic cosmic rays (GCR), trapped protons, and possible solar particle events (SPE) during spaceflight. For such complicated mixtures of radiation types and kinetic energies, tissue equivalent proportional counters (TEPC's) represent a simple time-dependent approach for radiation monitoring. Of interest in radiation protection is the average quality factor of a radiation field defined as a function of linear energy transfer, LET, Q(sub ave)(LET). However TEPC's measure the average quality factors as a function of lineal energy (y), Q(sub ave)(y) defined as the average energy deposition in a volume divided by the average chord length of the volume. Lineal energy, y deviates from LET due to energy straggling, delta-ray escape or entry, and nuclear fragments produced in the detector. Using integrated space radiation models that includes the transport code HZETRN/BRYNTRN, the quantum nuclear interaction model, QMSFRG, and results from Monte-Carlo track simulations of TEPC's response to ions, we consider comparisons of model calculations to TEPC results from NASA missions in low Earth orbit and make predictions for lunar and Mars missions. Good agreement between the model and measured spectra from past NASA missions is found. A finding of this work is that TEPC's values for trapped or solar protons of Q(sub ave)(y) range from 1.9-2.5, overestimating Q(sub ave)(LET), which ranges from 1.4-1.6 with both quantities increasing with shielding depth due to nuclear secondaries Comparisons for the complete GCR spectra show that Q(sub ave)(LET) for GCR is approximately 3.5-4.5, while TEPC's measure 2.9-3.4 for Q(sub ave)(y) with the GCR values decreasing with depth as heavy ions are absorbed in shielding material. Our results support the use of TEPC's for space radiation environmental monitoring when computational analysis is used for proper data interpretation.

Cucinotta, Francis A.↗
NASA NTRS2010

Radiation Measured with Different Dosimeters for ISS-Expedition 18-19/ULF2 on Board International Space Station during Solar Minimum

Radiation field of particles in low Earth orbit (LEO) is mainly composed of galactic cosmic rays (GCR), solar energetic particles and particles in SAA (South Atlantic Anomaly). GCR are modulated by solar activity, at the period of solar minimum activity, GCR intensity is at maximum and the main contributor for space radiation is GCR. At present for space radiation measurements conducted by JSC (Johnson Space Center) SRAG (Space Radiation Analysis Group), the preferred active dosimeter sensitive to all LET (Linear Energy Transfer) is the tissue equivalent proportional counter (TEPC); the preferred passive dosimeters are thermoluminescence dosimeters (TLDs) and optically stimulated luminescence dosimeters (OSLDs) sensitive to low LET as well as CR-39 plastic nuclear track detectors (PNTDs) sensitive to high LET. For the method using passive dosimeters, radiation quantities for all LET can be obtained by combining radiation results measured with TLDs/OSLDs and CR-39 PNTDs. TEPC, TLDs/OSLDs and CR-39 detectors were used to measure the radiation field for the ISS (International Space Station) - Expedition 18-19/ULF2 space mission which was conducted from 15 November 2008 to 31 July 2009 - near the period of the recent solar minimum activity. LET spectra (differential and integral fluence, absorbed dose and dose equivalent) and radiation quantities were measured for positions TEPC, TESS (Temporary Sleeping Station, inside the polyethylene lined sleep station), SM-P 327 and 442 (Service Module - Panel 327 and 442). This paper presents radiation LET spectra measured with TEPC and CR-39 PNTDs and radiation dose measured with TLDs/OSLDs as well as the radiation quantities combined from results measured with passive dosimeters.

Zhou, Dazhuang↗
NASA NTRS2011

Polymeric Materials With Additives for Durability and Radiation Shielding in Space

Polymeric materials are attractive for use in space structures because of their light weight and high strength In addition, polymers are made of elements with low atomic numbers (Z), primarily carbon (C), hydrogen (H), oxygen (0), and nitrogen (N) which provide the best shielding from galactic cosmic rays (GCR) (ref. 1). Galactic cosmic rays are composed primarily of nuclei (i.e., fully ionized atoms) plus a contribution of about 2% from electrons and positrons. There is a small but significant component of GCR particles with high charge (Z > 10) and high energy (E >100 GeV) (ref. 2). These so-called HZE particles comprise only 1 to 2% of the cosmic ray fluence but they interact with very high specific ionization and contribute 50% of the long- term dose to humans. The best shield for this radiation would be liquid hydrogen, which is not feasible. For this reason, hydrogen-containing polymers make the most effective practical shields. Moreover, neutrons are formed in the interactions of GCR particles with materials. Neutrons can only lose energy by collisions or reactions with a nucleus since they are uncharged. This is a process that is much less probable than the Coulombic interactions of charged particles. Thus, neutrons migrate far from the site of the reaction in which they were formed. This increases the probability of neutrons reaching humans or electronic equipment. Fast neutrons (> 1 MeV) can interact with silicon chips in electronic equipment resulting in the production of recoil ions which can cause single event upsets (SEU) in sensitive components (ref. 3). Neutrons lose energy most effectively by elastic collisions with light atoms, particularly hydrogen atoms. Therefore, hydrogen-containing polymers are not only effective in interacting with GCR particles; they are also effective in reducing the energy of the neutrons formed in the interactions.

Kiefer, Richard↗
NASA NTRS2004

The Feasibility of Multipole Electrostatic Radiation Shielding

Although passive shielding appears to be the only workable solution for galactic cosmic radiation (GCR), active shielding may play an important augmenting role to control the dose from solar particle events (SPEs). It has been noted that, to meet the guidelines of NCRP Report No. 98 through the six SPEs of 1989, a crew member would need roughly double the passive shielding that is necessary to control the GCR dose . This would dramatically increase spacecraft mass, and so it has been proposed that a small but more heavily shielded storm shelter may be used to protect the crew during SPEs. Since a gradual SPE may last 5 or more days, staying in a storm shelter may be psychologically and physiologically distressing to the crew. Storm shelters do not provide shielding for the spacecraft itself against the SPE radiation, and radiation damage to critical electronics may result in loss of mission and life. Single-event effects during the radiation storm may require quick crew response to maintain the integrity of the spacecraft, and confining the crew to a storm shelter prohibits their attending to the spacecraft at the precise time when that attention is needed the most. Active shielding cannot protect against GCR because the particle energies are too high. Although lower energy particles are easier to stop in a passive shield, such shielding is more satisfactory against GCR than against SPE radiation because of the tremendous difference in their initial fluences. Even a small fraction of the SPE fluence penetrating the passive shielding may result in an unacceptably high dose. Active shielding is more effective than passive shielding against SPE radiation because it offers 100% shielding effectiveness up to the cutoff energy, and significant shielding effectiveness beyond the cutoff as well.

Metzger, Philip T.↗
NASA NTRS2012

Miniaturized Gas Correlation Radiometer for the Detection of Trace Gases in the Martian Atmosphere

We present a miniaturized and simplified version of a gas correlation radiometer (GCR) capable of simultaneously mapping multiple trace gases and identifying active regions on the Mars surface. Gas correlation radiometry (GCR) has been shown to be a sensitive and versatile method for detecting trace gases in Earth's atmosphere. Reduction of the size and mass of the GCR was achieved by implementing compact, light-weight 1 mm inner diameter hollow-core optical fibers (hollow waveguides) as the gas correlation cells. In a comparison with an Earth orbiting CO2 GCR instrument, exchanging the 10 m multipass cells with hollow waveguide gas correlation cells of equivalent path length reduces the mass from approximately 150 kg to approximately 0.5 kg, and reduces the volume from 1.9 m x 1.3 m x 0.86 m to a small bundle of fiber coils approximately 1 meter in diameter by 0.05 m in height (mass and volume reductions of greater than 99%). A unique feature of this instrument is its stackable module design, with a single module for each trace gas. Each of the modules is self-contained, and fundamentally identical; differing by the bandpass filter wavelength range and gas mixtures inside the hollow-waveguide absorption cells. The current configuration contains four stacked modules for simultaneous measurements of methane (CH4), formaldehyde (H2CO), water vapor (H2O), and deuterated water vapor (HDO) but could easily be expanded to include measurements of additional species of interest including nitrous oxide (N2O), hydrogen sulfide (H2S), methanol (CH3OH), and sulfur dioxide (SO2), as well as carbon dioxide (CO2) for a simultaneous measure of mass balance. Preliminary results indicate that a 1 ppb detection limit is possible for both formaldehyde and methane with one second of averaging. Using non-optimized components, we have demonstrated an instrument sensitivity equivalent to approximately 30 ppb for formaldehyde, and approximately 500 ppb for methane. We expect custom bandpass filters and 6 m long waveguides to significantly improve these promising results. Ongoing testing is being conducted on water vapor and deuterated water vapor.

Melroy, Hilary R.↗
NASA NTRS2013

NASA Models of Space Radiation Induced Cancer, Circulatory Disease, and Central Nervous System Effects

The risks of late effects from galactic cosmic rays (GCR) and solar particle events (SPE) are potentially a limitation to long-term space travel. The late effects of highest concern have significant lethality including cancer, effects to the central nervous system (CNS), and circulatory diseases (CD). For cancer and CD the use of age and gender specific models with uncertainty assessments based on human epidemiology data for low LET radiation combined with relative biological effectiveness factors (RBEs) and dose- and dose-rate reduction effectiveness factors (DDREF) to extrapolate these results to space radiation exposures is considered the current "state-of-the-art". The revised NASA Space Risk Model (NSRM-2014) is based on recent radio-epidemiology data for cancer and CD, however a key feature of the NSRM-2014 is the formulation of particle fluence and track structure based radiation quality factors for solid cancer and leukemia risk estimates, which are distinct from the ICRP quality factors, and shown to lead to smaller uncertainties in risk estimates. Many persons exposed to radiation on earth as well as astronauts are life-time never-smokers, which is estimated to significantly modify radiation cancer and CD risk estimates. A key feature of the NASA radiation protection model is the classification of radiation workers by smoking history in setting dose limits. Possible qualitative differences between GCR and low LET radiation increase uncertainties and are not included in previous risk estimates. Two important qualitative differences are emerging from research studies. The first is the increased lethality of tumors observed in animal models compared to low LET radiation or background tumors. The second are Non- Targeted Effects (NTE), which include bystander effects and genomic instability, which has been observed in cell and animal models of cancer risks. NTE's could lead to significant changes in RBE and DDREF estimates for GCR particles, and the potential effectiveness of radiation mitigator's. The NSRM- 2014 approaches to model radiation quality dependent lethality and NTE's will be described. CNS effects include both early changes that may occur during long space missions and late effects such as Alzheimer's disease (AD). AD effects 50% of the population above age 80-yr, is a degenerative disease that worsens with time after initial onset leading to death, and has no known cure. AD is difficult to detect at early stages and the small number of low LET epidemiology studies undertaken have not identified an association with low dose radiation. However experimental studies in mice suggest GCR may lead to early onset AD. We discuss modeling approaches to consider mechanisms whereby radiation would lead to earlier onset of occurrence of AD. Biomarkers of AD include amyloid beta (A(Beta)) plaques, and neurofibrillary tangles (NFT) made up of aggregates of the hyperphosphorylated form of the micro-tubule associated, tau protein. Related markers include synaptic degeneration, dentritic spine loss, and neuronal cell loss through apoptosis. Radiation may affect these processes by causing oxidative stress, aberrant signaling following DNA damage, and chronic neuroinflammation. Cell types to be considered in multi-scale models are neurons, astrocytes, and microglia. We developed biochemical and cell kinetics models of DNA damage signaling related to glycogen synthase kinase-3(Beta) (GSK3(Beta)) and neuroinflammation, and considered multi-scale modeling approaches to develop computer simulations of cell interactions and their relationships to A(Beta) plaques and NFTs. Comparison of model results to experimental data for the age specific development of A(Beta) plaques in transgenic mice will be discussed.

Cucinotta, Francis A.↗
NASA NTRS2015

Galactic Cosmic Ray Simulator at the NASA Space Radiation Laboratory

The external Galactic Cosmic Ray (GCR) spectrum is significantly modified when it passes through spacecraft shielding and astronauts. One approach for simulating the GCR space radiation environment is to attempt to reproduce the unmodified, external GCR spectrum at a ground based accelerator. A possibly better approach would use the modified, shielded tissue spectrum, to select accelerator beams impinging on biological targets. NASA plans for implementation of a GCR simulator at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory will be discussed.

Norbury, John W.↗
NASA NTRS2016

Electromagnetic Dissociation and Spacecraft Electronics Damage

When protons or heavy ions from galactic cosmic rays (GCR) or solar particle events (SPE) interact with target nuclei in spacecraft, there can be two different types of interactions. The more familiar strong nuclear interaction often dominates and is responsible for nuclear fragmentation in either the GCR or SPE projectile nucleus or the spacecraft target nucleus. (Of course, the proton does not break up, except possibly to produce pions or other hadrons.) The less familiar, second type of interaction is due to the very strong electromagnetic fields that exist when two charged nuclei pass very close to each other. This process is called electromagnetic dissociation (EMD) and primarily results in the emission of neutrons, protons and light ions (isotopes of hydrogen and helium). The cross section for particle production is approximately defined as the number of particles produced in nucleus-nucleus collisions or other types of reactions. (There are various kinematic and other factors which multiply the particle number to arrive at the cross section.) Strong, nuclear interactions usually dominate the nuclear reactions of most interest that occur between GCR and target nuclei. However, for heavy nuclei (near Fe and beyond) at high energy the EMD cross section can be much larger than the strong nuclear interaction cross section. This paper poses a question: Are there projectile or target nuclei combinations in the interaction of GCR or SPE where the EMD reaction cross section plays a dominant role? If the answer is affirmative, then EMD mechanisms should be an integral part of codes that are used to predict damage to spacecraft electronics. The question can become more fine-tuned and one can ask about total reaction cross sections as compared to double differential cross sections. These issues will be addressed in the present paper.

Norbury, John W.↗
NASA NTRS2012

Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study

The key objectives of this study are to investigate, both computationally and experimentally, which forms, compositions, and layerings of hydrogen, boron, and nitrogen containing materials will offer the greatest shielding in the most structurally robust combination against galactic cosmic radiation (GCR), secondary neutrons, and solar energetic particles (SEP). The objectives and expected significance of this research are to develop a space radiation shielding materials system that has high efficacy for shielding radiation and that also has high strength for load bearing primary structures. Such a materials system does not yet exist. The boron nitride nanotube (BNNT) can theoretically be processed into structural BNNT and used for load bearing structures. Furthermore, the BNNT can be incorporated into high hydrogen polymers and the combination used as matrix reinforcement for structural composites. BNNT's molecular structure is attractive for hydrogen storage and hydrogenation. There are two methods or techniques for introducing hydrogen into BNNT: (1) hydrogen storage in BNNT, and (2) hydrogenation of BNNT (hydrogenated BNNT). In the hydrogen storage method, nanotubes are favored to store hydrogen over particles and sheets because they have much larger surface areas and higher hydrogen binding energy. The carbon nanotube (CNT) and BNNT have been studied as potentially outstanding hydrogen storage materials since 1997. Our study of hydrogen storage in BNNT - as a function of temperature, pressure, and hydrogen gas concentration - will be performed with a hydrogen storage chamber equipped with a hydrogen generator. The second method of introducing hydrogen into BNNT is hydrogenation of BNNT, where hydrogen is covalently bonded onto boron, nitrogen, or both. Hydrogenation of BN and BNNT has been studied theoretically. Hyper-hydrogenated BNNT has been theoretically predicted with hydrogen coverage up to 100% of the individual atoms. This is a higher hydrogen content than possible with hydrogen storage; however, a systematic experimental hydrogenation study has not been reported. A combination of the two approaches may be explored to provide yet higher hydrogen content. The hydrogen containing BNNT produced in our study will be characterized for hydrogen content and thermal stability in simulated space service environments. These new materials systems will be tested for their radiation shielding effectiveness against high energy protons and high energy heavy ions at the HIMAC facility in Japan, or a comparable facility. These high energy particles simulate exposure to SEP and GCR environments. They will also be tested in the LaRC Neutron Exposure Laboratory for their neutron shielding effectiveness, an attribute that determines their capability to shield against the secondary neutrons found inside structures and on lunar and planetary surfaces. The potential significance is to produce a radiation protection enabling technology for future exploration missions. Crew on deep space human exploration missions greater than approximately 90 days cannot remain below current crew Permissible Exposure Limits without shielding and/or biological countermeasures. The intent of this research is to bring the Agency closer to extending space missions beyond the 90-day limit, with 1 year as a long-term goal. We are advocating a systems solution with a structural materials component. Our intent is to develop the best materials system for that materials component. In this Phase I study, we have shown, computationally, that hydrogen containing BNNT is effective for shielding against GCR, SEP, and neutrons over a wide range of energies. This is why we are focusing on hydrogen containing BNNT as an innovative advanced concept. In our future work, we plan to demonstrate, experimentally, that hydrogen, boron, and nitrogen based materials can provide mechanically strong, thermally stable, structural materials with effective radiation shielding against GCR, SEP, and neutrons.

Radiation↗
NASA NTRS2018

The International Space Station Space Radiation Environment: Avionics Systems Performance in Low-Earth Orbit Single Event Effects (SEE) Environments

Single event effects (SEE) are those errors, anomalies, or failures in microelectronic devices caused by the passage of a single energetic charged particle through the device. Spacecraft SEE environments consist primarily of energetic charged particles; both primary particles originating in the natural environment and secondary particles (including secondary neutrons) produced by nuclear reactions of primary particles with spacecraft materials. The energetic charged particle components (electrons, protons, and atomic nuclei) of the spacecraft SEE environment include galactic cosmic rays (GCR), and planetary radiation belt charged particles, as well as solar energetic particle event (SPE) charged particles. The International Space Station (ISS) orbital altitude and inclination (~350 km to ~420 km at 51.6o inclination) results in a spacecraft SEE environment that varies dramatically with the location in Earth?s geomagnetic field. Geomagnetic GCR shielding diminishes with distance from the geomagnetic equator. Near + 51.6o latitude the ISS GCR environment has a high degree of similarity to the interplanetary GCR environment in cis-Lunar space.SEE environments supporting ISS avionics systems design, development, test, and verification are documented in SSP-30512, Space Station Ionizing Radiation Design Environment. Comparisons of overall ISS avionics systems in-flight performance with pre-flight verification report predictions have been previously reported and meet or exceed expectations in all cases.In this paper we report the results of more detailed investigations of the effects of geographic location, altitude, solar cycle, and shielding mass effects on the in-flight SEE performance of the ISS command and data handling system during the past 17 years. In addition, we report on the preflight testing and in-flight performance of the commercial-off-the-shelf lap top computers used on ISS. Finally, we present an assessment of ISS as an avionics SEE test and flight demonstration platform for exploration hardware destined for the cis-lunar or other inner solar system environments.

International Space Station↗
NASA NTRS2018

Maintaining Human Health for Humans-Mars

The Human Health Research Program states that Radiation is the most challenging hazard to human spaceflight beyond LEO. The International Space Station provides an analog for evaluating techniques for dealing with Altered Gravity, the Radiation Environment of the ISS is only about 45% of the deep space values where radiation due to Galactic Cosmic Rays (GCR) dominate the spectrum. The Moon and cis-lunar space are being considered as a Mars Analog training ground for preparing crews for human mission to Mars. Spending more than 200 days in deep space is considered unsafe based on our current proxy for lifetime radiation dose. The paper outlines a way forward for spending days training near the Moon and for completing roundtrip missions to Mars while remaining below the current proxy. In the first case, a GCR overcoat shields crews from radiation during cis-lunar activities before making fast transits without in-space GCR overcoats to and from Mars. This case requires continued maturation of low TRL propulsion and power technologies currently around 4 to 5 while depending on repeatable reductions in launch costs by a factor of 6 expected of current reusable rockets. The second case requires no new technology development except for the expectation that the next near-term generation of reusable rockets will reduce launch costs by a factor of around 14. Five trajectories and GCR overcoat sizes for all mission legs are presented herein to illustrate the opportunities to maintain human health for Humans-Mars missions.

Robert W Moses↗
NASA NTRS2020

The Galactic Cosmic Ray Simulator at the NASA Space Radiation Research Laboratory

With NASA’s new Artemis plan for a sustainable return to the moon, astronauts will once again leave Earth’s protective magnetosphere only to endure higher levels of radiation from galactic cosmic radiation (GCR). The ever penetrating GCR will continue to pose significant health risks especially as lunar missions increase in duration and as NASA sets its aspirations on Mars. The primary risks of concern include carcinogenesis, central nervous system (CNS) effects resulting in potential in-mission cognitive or behavioral impairment and/or late neurological disorders, and degenerative tissue effects including circulatory and heart disease. Characterization and mitigation of these risks requires a significant reduction in the large biological uncertainties of chronic (low-dose rate) heavy ion exposures and the validation of countermeasures in a relevant space environment. Historically, most research on understanding space radiation-induced health risks has been performed using acute exposures of monoenergetic single-ion beams. However, the space radiation environment consists of a wide variety of ion species over a broad energy range. Using the fast beam switching and controls systems technology recently developed at the NASA Space Radiation Laboratory at Brookhaven National Laboratory, a new era in radiobiological research is possible. NASA has developed the “GCR simulator” to generate a spectrum of ion beams that approximates the primary and secondary GCR field experienced at human organ locations within a deep-space vehicle.

NASA Space Radiation Laboratory↗
NASA NTRSDate not supplied

Solar Energetic Particle Radiation Dosage Near a Simple Lunar Crater

The Moon has a harsh radiation environment that poses significant challenges to future science and exploration activities. Exposure hazards from space radiation are primarily due to galactic cosmic rays (GCRs) and solar energetic particles (SEPs) that are incident at the lunar surface from all directions. The Lunar Reconnaissance Orbiter’s (LRO) Cosmic Ray Telescope for Effects of Radiation (CRaTER) instrument has been observing space radiation around the Moon since 2009 [1].The CRaTER observations show as teady GCR flux with intermittent SEP events that have much higher fluxes. During solar minimum GCR shave a higher flux, while SEP events are less common. On the other hand, during solar maximum the SEP events have a higher rate, but the GCR flux is lower. This is due to variations in solar activity. GCR shave characteristic energies spanning from1 MeV to 10s of GeV[2]. SEPs, however, have much lower energy ranges of 50 keV to 100sof MeV. The level of exposure at a given location on the Moon is dependent on the amount of space radiation incident from above the local horizon(Figure 1). This means that radiation dosage depends on the surrounding terrain for any location on the surface, so it can vary substantially from point to point. Here we consider the radiation exposure around simple lunar craters that are representative of the types of landforms that will be encountered by future landed missions(e.g., the Artemis program)[3]. Of particular concern will be radiation exposure to biological targets, such as astronauts, and to critical electronic systems

P H Phipps↗
NASA NTRSDate not supplied

Galactic Cosmic Ray Proton Radiation Dosage Near a Simple Lunar Crater

The Moon has a harsh radiation environment that poses significant challenges to future science and exploration activities. Exposure hazards from space radiation are primarily due to galactic cosmic rays (GCRs) and solar energetic particles (SEPs) that are incident at the lunar surface from all directions. The Lunar Reconnaissance Orbiter’s (LRO) Cosmic Ray Telescope for Effects of Radiation (CRaTER)instrument has been observing space radiation around the Moon since 2009 [1].The CRaTER observations show a steady rate of GCR flux with intermittent SEP events that have much higher fluxes. During solar minimum the GCR have a higher flux rate while the SEP events are less common. On the other hand, during solar maximum the SEP events have a higher rate but the GCR flux is lower. This is due to variations in solar activity. GCR shave characteristic energies spanning from 1 MeV to 10s of GeV[2]. SEPs, however, have much lower energy ranges of 50 keV to 10 GeV. The level of exposure at a given location on the Moon is dependent on the amount of space radiation incident from above the local horizon(Figure 1). This means that, radiation dosage depends on the surrounding terrain for any location on the surface, so it can vary substantially from point to point. Here we consider the radiation exposure around simple lunar craters that are representative of the types of landforms that will be encountered by future landed missions(e.g., the Artemis program)[3]. Of particular concern will be radiation exposure to biological targets, such as astronauts, and to critical electronic systems.

P H Phipps↗
NASA NTRS2023

Observation of the Radiation Environment and Solar Energetic Particle Events in Mars Orbit in May 2018- June 2022

Epithermal Neutron Detector (FREND). Here we present results from measurements of the charged particle fluxes, dose rates and estimation of dose equivalent rates at ExoMars TGO Mars science orbit, provided by Liulin-MO from May 2018 to June 2022. The period of measurements covers the declining and minimum phases of the solar activity in 24th solar cycle and the rising phase of the 25th cycle. Compared are the radiation values of the galactic cosmic rays (GCR) obtained during the different phases of the solar activity. The highest values of the dose rate and flux from GCR are registered from March to August 2020. At the minimum of 24th and transition to 25th solar cycle the dose rate from GCR is 15.9 ± 1.6 µGy h−1, particle flux is 3.3 ± 0.17 cm−2 s−1, dose equivalent rate is 72.3 ± 14.4 µSv h−1. Since September 2020 the dose rate and flux of GCR decrease. Particular attention is drawn to the observation of the solar energetic particle (SEP) events in July, September and October 2021, February and March 2022 as well as their effects on the radiation environment on TGO during the corresponding periods. The SEP event during15–19 February 2022 is the most powerful event observed in our data. The SEP dose during this event is 13.8 ± 1.4 mGy (in Si), the SEP dose equivalent is 21.9 ± 4.4 mSv. SEP events recorded in Mars orbit are related to coronal mass ejections (CME) observed by SOHO and STEREO A coronagraphs. Compared are the time profiles of the count rates measured by Liulin-MO, the neutron detectors of FREND and neutron detectors of the High Energy Neutron Detector (HEND) aboard Mars Odyssey during 15–19 February 2022 event. The data obtained is important for the knowledge of the radiation environment around Mars, regarding future manned and robotic flights to the planet. The data for SEP events in Mars orbit during July 2021-March 2022 contribute to the details on the solar activity at a time when Mars is on the opposite side of the Sun from Earth.

Jordanka Semkova↗
NASA NTRSDate not supplied

Artemis 1 Radiation Modeling and Analysis Using Operational Methods

The successful completion of the Artemis 1 mission has provided NASA with a significant volume of space radiation dosimetry data that can be used to verify the accuracy of current operational SRAG dose computation models and methods for Beyond LEO missions. High-Fidelity CAD models of the Artemis 1 MPCV Orion were raytraced in 10,000 directions per sensor location, including the location of Artemis HERA sensors, Artemis RAMs (TLDs), and the crew active dosimetry (CADs). The full Artemis 1 mission was modelled using the as-flown trajectory, Ap9-Ae9 IRENE providing the VAB trapped proton and electron environment, and the Badhwar-O’Neill 2020 model providing the freespace GCR environment. IGRF 12 was used to compute cutoff rigidities for the GCR environment in LEO. 1DHZETRN was used to estimate point doses at each sensor position. Computed RAM doses were within 5% of measured values. The computed VAB transit and freespace GCR dose rates showed good qualitative agreement with measured HERA values. An estimate of normalized mean effective dose for a hypothetical male crew member on Artemis 1 using current standard operational methods was computed to be 22.3 mSv.

Artemis 1↗
NASA NTRS1984

The isotopic composition of the anomalous low-energy cosmic rays

Measurements of the isotopes of low energy cosmic ray He, C, N, O and Ne nuclei are analyzed, in concert with previous data, to examine relationships between galactic cosmic rays (GCR) and anomalous cosmic rays (ACR), which could arise from either extragalactic or interstellar sources. A ground-based heavy isotope spectrometer telescope was used for the survey, along with IMP-7 and IMP-8 data and ISEE-3 data. The data were recorded from 1973-78. Spectral and abundance data are provided for each element. Fragmentation was absent in the ACR data, unlike the GCR data. Differences were also observed in the Ne-22/Ne-20 ratios of ACR and GCR. It is suggested, therefore, that the low energy ACR isotopes have an interstellar origin and are useful for studies of the local interstellar medium.

Mewaldt, R. A.↗
NASA NTRS1985

Galactic cosmic ray currents and magnetic field irregularity degree in high-speed solar wind streams

Currents of galactic cosmic rays (GCR) obtained by global survey method are analyzed. The cases of almost total disappearance of GCR currents are compared with the results of direct measurements of the solar wind parameters. The conclusion is made on a restricted application of the convective-diffusive mechanism of the GCR modulation by the solar wind during the occurrence of stationary and regular magnetic fields in the interplanetary medium.

Kuzmin, A. I.↗