THREE Encyclopedia

* Denotes a previously Featured Article

NASA and Exploration

Exploration, as understood by the space community, implies a human presence in space. The purpose of this section is to provide a context for this presence, branching out from the NASA perspective to a history of the space exploration efforts of the other spacefaring nations. The rationale for the US space effort has been evolving continuously since President Kennedy called for putting a man on the moon in response to Sputnik. “Visions” have been iterated several times, reflecting changing perceptions of national purpose. However, the elements of foreseeable missions have been defined and can be expected to be a part of whatever future strategies are adopted. Space exploration is a truly international effort. It is intended that this section will also host descriptions of the efforts of NASA’s partners in the future. In addition to joint efforts with the US Department of Energy described in the current articles, NASA has a long history of collaboration with other agencies of the Federal Government. More articles describing this collaboration are also planned.

  • NASA’s Mission - Frank Sulzman (HTML)
  • Space Flight History - Gregory Nelson (Article)

  • NASA Space Radiation Program: Interagency Collaboration - Walter Schimmerling (PDF)
  • European Space Agency - M. Durante (PDF)
  • Low Dose Radiation Research Program (PDF)
  • National Institute of Allergy and Infectious Diseases (NIAID) "Preparations for Mitigation and Treatment of Injuries from a Radiation Incident - Andrea L DiCarlo-Cohen (PDF)

Basic Concepts of Space Radiation

In order to understand the space radiation risks faced by human explorers, it is necessary to have a clear idea of what it is, where it is, and what happens when space radiation interacts with matter. The articles in this section describe the space radiation environment, the nuclear and atomic interactions with the constituent atoms of materials – especially living materials – in space, and the ways in which energy is deposited in biologically significant molecules.

Some of the articles are taken from the Appendices of a 1998 Strategic Plan I authored during my tenure at NASA and others are presentations given by NASA Summer School faculty. There is a fair amount of overlap, both within this section and between this section and other sections, where the subjects are discussed in greater detail. This is welcome, reflecting as it does, different – and broadening – perspectives on the topics covered.

Walter Schimmerling

THREE Chief Editor

  • The Natural space Ionizing Radiation Environment* - Patrick O’Neill (Article)
  • Solar Particle Events and Radiation Exposure in Space* - Shaowen Hu (PDF)
  • Fluence Rates, Delta Rays and Cell Nucleus Hit Rates from Galactic Cosmic Rays - Stanley Curtis (PDF)

  • Interactions of Radiation with Matter - Walter Schimmerling (Article)
  • Particle Interactions Overview - Lawrence Heilbronn (HTML)
  • Neutron Lectures Supplement - Lawrence Heilbronn (PDF)
  • Physics Summary - Lawrence Heilbronn (HTML)
  • Neutron Properties and Definitions - Lawrence Heilbronn (HTML)

  • Dose and Dose Rate Effectiveness Factors - Walter Schimmerling (Article)
  • A Note On The Dose-Rate-Effectiveness Factor and its Progeny DDREF - R.J.M. Fry (PDF)
  • Low LET Physics Topics - Gregory Nelson (HTML) Introduction (PDF)

  • Introduction to Track Structure and z*2/ß2 - Stanley Curtis (PDF)
  • Radiation Quality and Space Radiation Risks - Francis Cucinotta (PPT)
  • Microdosimetry and Detector Responses - Leslie A. Braby (PDF)
  • Development of Monte Carlo Track Structure Codes - Larry Toburen (PDF)
  • Interpreting Microdosimetric Spectra - J. F. Dicello, Francis Cucinotta (PDF)
  • Monte Carlo Track Simulations - Michael Dingfelder (PDF)
  • Radiation Track Structure - Dudley T. Goodhead (HTML) Abstract (PDF)
  • Track structure and the quality factor for space radiation cancer risk - Dudley T. Goodhead (PDF)

  • Elementary Concepts of Shielding - Walter Schimmerling (PDF)
  • Heavy Ions and Shielding Physics - Lawrence Heilbronn (HTML)

Proton and HZE Accelerator Sources

Ground-based accelerator exposure facilities provide beams of protons and HZE particles, at energies within the range of space radiation. The main purpose of simulating space radiation at these facilities is to determine the biological factors of risk. However, they can also be used to obtain required data on the physical interactions of these beams with materials and space instruments. Data about the interaction of HZE particles with materials is required especially for the design of light-weight optimized shielding configurations. The calibration and design of instruments is required in order to interpret reliably the data about the space radiation environment collected on Shuttle, Mir, Space Station, in robotic precursor missions and other assets.

Research into the risks of space radiation to human explorers has a fundamental advantage over research into other risks in that all relevant components of space radiation can be delivered as beams by ground-based charged particle accelerators, thus simulating the space radiation environment.

Some further articles on this topic, listed in the Bibliography, that may be consulted for current information, are:

Walter Schimmerling
THREE Chief Editor

  • Accelerators Made Simple - Derek Lowenstein (PPT) Introduction (PDF)
  • Accelerator-based Space Physics - Cary Zeitlin, Lawrence Heilbronn, John Norbury (HTML)
  • Accelerator-based Sources of Albedo Neutrons - Lawrence Heilbronn (PDF)
  • NASA Space Radiation Laboratory* - Derek Lowenstein, Peter Guida, Adam Rusek (PDF)
  • A New Low Energy Irradiation Facility at BNL* - P. Thieberger (PDF)
  • The Galactic Cosmic Ray Simulator at the NASA Space Radiation Research Laboratory* - Lisa C. Simonsen, Tony C. Slaba, Peter Guida, Adam Rusek (Article)

  • Ion Microbeams and Their Role in Radiobiology Research in Europe - B.E. Fischer (PDF)
  • High/Low LET Microbeams - Gerhard Randers-Pehrson (HTML)

Radiation Measurements

The interaction of radiation with living tissues leads to a deposition of energy that we call “dose.” The detection of radiation and the measurement of the ways in which that energy is deposited is a science in itself. These articles cover the ways in which space radiation is detected and how the detector signals can be interpreted to yield an understanding of dose, the first event in the sequence of events leading to the evaluation of space radiation risk.

Walter Schimmerling
THREE Chief Editor

  • Space Radiation Dosimetry - Walter Schimmerling (Article)
  • Dosimetry - Lawrence Heilbronn (HTML)
  • Detection Methods - Lawrence Heilbronn (HTML)
  • Cosmic Ray Detectors: Principles of Operation and a Brief Overview of (Mostly) U.S. Flight Instruments - Cary Zeitlin (PDF)
  • Space Radiation Passive Dosimetry - Eric Benton (PDF)
  • Exploration Systems Radiation Monitoring Requirements - Ronald Turner (PDF)
  • Biological Dosimetry in Astronauts - Kerry George (PDF)
  • MATROSHKA - A research Platform for Reducing Radiaton Risk in Space - Guenther Reitz (PDF)
  • Current Active Detectors for Dosimetry and Spectrometry on the International Space Station - Cary Zeitlin, Larry Pinsky (Article)

Radiation Chemistry

In the first few picoseconds after the passage of radiation through a target, the deposited energy is stored in electrons and excited or ionized atoms and molecules. This is the “chemical stage” preceding the events that lead to space radiation risk. It is considered to last until the radicals and electrons have diffused and combined (or re-combined) to form stable chemical species. The yield of the radicals and molecular reaction products is the province of radiation chemistry.

The chemical changes constitute information that may remain readable for a long time, whether as tracks in an emulsion or deletions in DNA. However, readout of the information stored in this manner on biologically relevant molecules, while also involving chemistry, is properly considered part of a biological stage.

Walter Schimmerling
THREE Chief Editor

  • Yields of Chemical Species - Jay LaVerne (PDF)
  • Radiation chemistry and oxidative stress - Ianik Plante (PDF)
  • Energetic and chemical reactivity of atomic and molecular oxygen - Ianik Plante (PDF)
  • An Assessment of How Radiation Incurred During a Mars Mission Could Affect Food and Pharmaceuticals - Myung-Hee Y. Kim, Ianik Plante (PDF)
  • Radiation Chemistry and DNA Damage - Peter O'Neill (PDF)
  • Essentials of Mammalian DNA Repair - Paul Wilson (HTML)
  • Oxygen in Space Radiation Biology - Paul Todd (PDF)

Systems Biology

What is a "system"? In common definitions, it is an organized assembly of parts, having some common purpose, and that allows consideration as a whole, without the need to take the characteristics of each part (which may also be a system) into account. For example, a gas in a container is a system, and the temperature and pressure are system properties, which can be measured without any knowledge of the properties of the individual molecules. More generally, any phase of matter, characterized by a more or less homogeneous composition, a defined extension, long-range order, and a limiting surface, can be considered a system. Evidently, any assembly of systems is also a system.

In statistical mechanics, systems consisting of identical particles are referred to as ensembles, and their properties depend on whether their number is constant or variable, and on whether they can exchange energy with external reservoirs or not. From that point of view, living systems are so-called "grand canonical ensembles," since the number of cells can change and they are in equilibrium with the surrounding environment. Thus, systems biology is an extension of statistical mechanics by other means, the means mainly being an understanding of the chemical reactions that take place between living cells and regulate their number. In order to make accurate predictions of unforeseen consequences, it is necessary to understand the nature of the interactions that occur at a level of detail greater than a collection of average values and their fluctuations. That is what "systems biology" intends to accomplish.

A proper approach to systems biology begins with a judicious characterization of the "system". This has been implicit in theoretical approaches throughout the history of radiation biology, even if the ideas peculiar to systems were not always made explicit. If the only interactions to be considered are those that occur within the cell nucleus during a short interval, then the "system" need not be larger than the collection of chemical reactions that ensue after exposure. However, once interaction between the initial chemical reaction products occurs, and the information content - entropy - of the nucleus is significantly altered so that its extent and common properties change, the question becomes whether the contents of the nucleus will undergo a change of phase, melting the nucleus from an ordered, information-storage-and-generating phase to a disordered soup of amino acids. In that case, the "system" is the cell, because information is exchanged between the cell and its nucleus, changes in entropy are driven by energy use and storage, and the equilibrium between the epigenetic environment of the cell and its nucleus can be disturbed.

On a time scale comparable to the transfer of information between cells, the proper "system" may be an organ instead of a cell; the organ now considered as a different phase of matter (defined extension, common function, entropy constant across the tissue, etc.). The perturbation of this system by its subsystems does not require a knowledge of events at very small time scales, or of microscopic velocity distributions. Presumably, every cell affected by the radiation dose will have reached an asymptotic state, and changes in its significant signalling properties can now be described in terms of a reduced number of variables, such as the concentrations of a limited number of signalling molecules.

This problem is very similar to cosmological observations like the expansion of the universe, the microwave background radiation, etc. Most questions do not depend on detailed characteristics of the Big Bang and the first instants after it, but many interesting questions do. However, if you are trying to calculate the fuel requirements for an interplanetary mission, you can safely assume that gravitation is what it is now, that the Sun will be in place during the mission, and that your spacecraft will not suddenly disintegrate into quarks.

However, if you ask questions about the lack of antimatter in our neighborhood, or the mass of elementary particles, or the temperature of the microwave background, you need to consider a different "system", which is likely to include microscopic events at early times in the universe. Similarly, when you ask questions about the probability of having cells lose their information so that they become cancerous, and about their ability to "melt" the phase that we call a tissue into a disorganized state, then the "system" must include multiple pathways - networks - to describe the ways in which cells signal each other and the ways in which those signals control the entropy of the tissue phase. Such networks are conceptually not very different from classical Feynman diagrams or the formalism of creation and destruction operators used to describe elementary particle interactions.

A quantitative description of such networks requires a calculation of the chemical potentials of all relevant signalling molecules. Such a calculation, in turn, requires an understanding of rate constants, unfortunately considered a black art. However, in fact, the relevant proteins are not infinite in number, and perhaps only a small number dominate processes in any given tissue. The structure of molecules is being derived at an explosive pace and, given elementary knowledge of their velocities it is not inconceivable that the probability that they will connect with different other molecules, as a function of time, can be calculated and verified by measurement.

A fertile adoption of systems concepts thus would seem to consist of an analysis of the networks associated with chemical reaction pathways and development of the tools necessary to describe their microchemical underpinnings. An understanding of the mechanisms driving such network phenomena would seem to be essential for accurate predictions of the undesirable outcomes we characterize as risks. However, such an understanding of details would also lead to realistic ways of modulating the steady state of any such network and, therefore, preventing some of the consequences. At the very least, such an understanding would lead to earlier diagnostic tools that could be combined with standard treatment to achieve improved results.

The articles that follow sample the many imaginative ways in which radiation biologists attempt to approach the opportunities offered by systems biology.

Walter Schimmerling
THREE Chief Editor

  • Kinetics, Systems Biology and other Models - Francis Cucinotta (HTML)
  • A Systems Biology Approach to Radiation Biology - Mary Helen Barcellos-Hoff (PDF)
  • Radiation-perturbed signalling and systems radiation biology - Luca Mariotti , Andrea Ottolenghi (PDF) (Revised)
  • Systems Radiation Biology and Radiation Induced Cell Signals - Mary Helen Barcellos-Hoff (PDF)
  • Signal transduction processes in response to low dose ionizing radiation doses expected during space flight - David Boothman, Tracy Criswell, Eva Goetz, Dmitri Klokov, Yonglong Zou, Xinjian Liu (PDF)
  • MALDI-MSI: Biomarker Discovery for Radiation Exposures - Claire L. Carter, Thomas J. MacVittie, Maureen A. Kane (PDF)
  • Developing omics-based approaches for short- and long-term space radiation risk assessment* - Kamal Datta, Shubhankar Suman, Daniel Hyduke, Jerry W. Shay, Albert J. Fornace Jr. (PDF)

Cell Damage and Repair

Cells, aggregated into the systems we call organs and tissues, are the fundamental building blocks of organisms. The understanding of space radiation risks passes through an understanding of the interaction of radiation with living cells. This section contains a series of NASA Summer School lectures presenting many of the multiple aspects of the effects of radiation on cells: their constitutive molecules, the organelles within them, and some of the processes affected by radiation.

Walter Schimmerling
THREE Chief Editor

  • Radiobiology I - Eric Hall (HTML)
  • Biological Responses to High LET Radiation - Eric Hall (HTML)
  • Oxidative Stress - Peter O'Neill (HTML)
  • MicroRNAs (miRNAs), the Final Frontier: The Hidden Master Regulators Impacting Biological Response in All Organisms Due to Spaceflight* - Charles Vanderburg, Afshin Beheshti (Article)
  • The Effects of Space Radiation-changed MiRNAs on Tumorigenesis - Ya Wang (PDF)
  • Mammalian DNA Damage Responses - Carl Anderson (HTML)
  • DNA Repair - HZE Damaged DNA - Susan Bailey (HTML)
  • RNA Transcription Factors and R-Loops - David Boothman (PDF)
  • Precise Genome Engineering and the CRISPR Revolution (Boldly Going Where No Technology Has Gone Before.)* - Eric A. Hendrickson (PDF)
  • Radiosensitivity and the Cell Cycle - Michael Joiner (HTML)
  • The Use of Biomarkers to Predict Radiation Dose and Risk During Space Flights - Antone Brooks (PDF)
  • Using Flow Cytometry to Detect High-LET Radiation Induced Apoptosis and Necrosis - Peter Guida (HTML)
  • Abortive apoptosis and its profound effects on radiation-, chemical-, and oncogene induced carcinogenesis - Xinjian Liu, Ian Cartwright, Fang Li, Chuan-Yuan Li (PDF)
  • Stochastic Distribution of DNA Damage and Foci Formation - Artem Ponomarev (HTML)
  • Radiation Induced Foci Use and Abuse - Sylvain Costes (HTML)
  • Radiation-Induced Non-Targeted Effects - Edouard Azzam (HTML)
  • The Radiation Response in Cells Not Directly Traversed by High Charge and High Energy Particles: The Bystander Effect of Space Radiation - Edouard Azzam, Jason Domogauer (PDF)
  • Essentials of Mammalian DNA Repair - Paul Wilson (HTML)
  • Epigenetic Memory of Space Radiation Exposure* - Elizabeth M. Kennedy, Karen N. Conneely, Paula M. Vertino (PDF)
  • The Emerging Role of Exosomes in the Biological Processes Initiated by Ionizing Radiation - Munira A Kadhim, Scott J Bright, Ammar H J Al-Mayah, Edwin Goodwin (PDF)
  • Microglia Cells, The Brain Innate Immune System: Friend or Foe?* - Xi Feng, Karen Krukowski, Susanna Rosi, Maria Serena Paladini (Article)
  • Chromosomal Aberrations Cytogenetic Effects of Ionizing Radiation - Marco Durante (HTML)

Tissue Biology and Pathology

Tissues are the systems aggregated into living organisms. They can be regarded as the biological equivalent of chemical phases, having long range ordering with similar properties throughout their volume and, generally, being separated from other tissues by a defined surface. Thus, many of their characteristics can be understood without reference to the details of the underlying cellular functions. Systems biology is a fundamental modern paradigm, discussed currently in two articles, with several more to follow.

The articles in this section consider the response of different tissues to radiation from a broad perspective mainly based on studies with animal models of human behavior. NASA Summer School lectures are included wherever appropriate.

Walter Schimmerling
THREE Chief Editor

  • Animal Studies/Radiation Carcinogenesis - Michael Weil (HTML)
  • Animal Studies/Genetics - Michael Weil (HTML)
  • Transgenic Mouse Models and Novel Imaging Approaches - David Kirsch (HTML)
  • Summary of an integrated experimental and computational approach to study the effects of heavy ion exposures on skin - Jake Pirkkanen, Claere von Neubeck, Marianne B. Sowa (Article)

  • Space Radiation and the Central Nervous System: Potential Risks - M. Kerry O'Banion (PDF)
  • Radiation Effects in the Central Nervous System - M. Kerry O'Banion (HTML)
  • Neurogenesis - John Fike (HTML)
  • Radiation Response of Stem Cells and Neurons - John Fike (HTML)
  • An Introduction to Behavior Testing for the Radiobiologist - Bernard M. Rabin (Article)
  • Radiation Effects on Behavior - Bernard M. Rabin (HTML)
  • Space Radiation-Induced Cognitive Deficits Following Head-Only, Whole Body, or Body-Only Exposures* - Catherine M. Davis , Bernard M. Rabin (Article)
  • Microglia Cells, The Brain Innate Immune System: Friend or Foe?* - Xi Feng, Karen Krukowski, Susanna Rosi, Maria Serena Paladini (Article)
  • A Sankofian appraisal on how to maximize translatability of rodent space radiation/CNS studies to astronauts (Article)

  • Radiation Degenerative Risks - M. Kerry O'Banion (HTML)
  • Immune System - Gregory Nelson (HTML) Introduction (PDF)
  • The role of innate and adaptive immune system in the tissue responses to ionizing radiation - Sandra Demaria (HTML)
  • Aging and Cancer: Telomeres, Telomerase and Cancer - Jerry W. Shay (HTML) Introduction (PDF)

  • Cardiovascular Effects of Radiation - Fiona Stewart (PDF)
  • An introduction to space radiation and its effects on the cardiovascular system - Marjan Boerma (PDF)
  • Using Proteomics Approaches to Assess Mechanisms Underlying Low Linear Energy Transfer or Galactic Cosmic Radiation-Induced Cardiovascular Disease - Zachary D. Brown, Muath Bishawi, Dawn E. Bowles (PDF)

  • Cell and Animal Models of Lung Cancer - Jerry W. Shay (HTML) Introduction (PDF)
  • The Use of Human Epithelial Cells and Mouse Models of Human Lung Cancer for Space Radiation Research - Jerry W. Shay (HTML) Introduction (PDF)
  • Genetically Modified Mouse Models of Lung CancerEverett Moding and David Kirsch - Everett Moding , David Kirsch (PDF)
  • Solid Tumor Risk Estimation Outreach Project - Clare Lamont (HTML)

  • Radiation-Induced Leukemia - Michael Weil (HTML) Introduction (PDF)

Health Effects

The ultimate concern stemming from exposure of human beings to space radiation is the risk incurred, the probability of detrimental effects on their health. The articles in this section summarize much of what is known about such effects, mainly from exposure to terrestrial radiation. The NASA Summer School lectures are included and provide a link to the physical and biological sciences on which our understanding of the processes leading to space radiation risk is based.

Walter Schimmerling

THREE Chief Editor

  • Acute Effects 1 - Tom Seed (PDF)
  • Acute Effects 2 - Ann Kennedy (HTML) Introduction PDF
  • Radiobiology II - Eric Hall (HTML)
  • Normal Late Tissue Effects, Leukemia, Solid Tumors - Jacky Williams (HTML)

  • The use of biological countermeasures to reduce cancer risks from exposures to space radiation - Jerry W. Shay (HTML) (PDF)
  • Radioprotectors - Ann Kennedy (HTML) (PDF)
  • Medical countermeasures for extraterrestrial environments: Current status and future prospects with focus on acute injuries* - Vijay K. Singh, Thomas Seed (Article)

Radiation Therapy

Much of the science on which the understanding of space radiation risk is based was developed in the context of efforts to use charged particle beams for therapy of cancer. The purpose of therapy is, of course, the elimination of malignant cells. However, the evaluation of their therapeutic advantage requires that the "out of field" radiation leading to undesirable effects on healthy cells and tissues also be evaluated. As a consequence, there has been a historical link between laboratories studying charged particle radiotherapy, in particular, heavy ion radiotherapy, and their use as sources of radiation to simulate space radiation. In particular, NASA developed the NASA Space Radiation Laboratory. Even before then, NASA scientists had a significant role in developing research capabilities at the Lawrence Berkeley National Laboratory Bevalac facility and at the Loma Linda radiation therapy facility. The articles presented here summarize the work of major laboratories currently leading the field.

Walter Schimmerling
THREE Chief Editor

  • The Physics of Protons for Patient Treatment - Andrew J. Wroe, Jerry D. Slater, James M. Slater (PDF)
  • Rationale for, and Development of, the World's First Hospital-based Proton Therapy System at Loma Linda University Medical Center - James M. Slater (PDF)
  • Clinical Proton Therapy at Loma Linda University Medical Center - Jerry D. Slater (PDF)
  • Carbon-Ion Radiotherapy & Basic and Clinical Studies - Koichi Ando (PDF)
  • Heavy Ion Therapy at GSI - Marco Durante (PDF)
  • History of the Heavy Ion Therapy at GSI - Gerhard Kraft (PDF)
  • The Local Effect Model -; Principles and Applications - Thomas Friedrich, Marco Durante, Michael Scholz (PDF)
  • TOPAS-nBio: A Monte Carlo simulation toolkit for cell-scale radiation effects* - J. Schuemann, A. McNamara, J. Ramos, J. Perl, K. Held, H. Zhu, S. Incerti, H. Paganetti, B. Faddegon (Article)

Non-Radiation Risks

Space radiation risks occur in the context of humans subjected to all the other sources of risk in space. Most prominent among those is the modification of human function by weightlessness, the near-cancellation of gravitational acceleration by the acceleration required to remain in orbit, or the reduction of gravitational acceleration by distance from planetary masses. It has become customary to refer to these circumstances by the name of microgravity, although gravity, of course, continues undiminished as one of the known forces providing attraction between large masses.

That the effects of radiation upon an individual subject to weightlessness may be enhanced or modulated has been a matter of speculation since the dawn of the space age. Research on this matter is ongoing and may justify posting further articles in the future.

Walter Schimmerling

THREE Chief Editor

  • Microgravity Effects - Gregory Nelson (HTML) Introduction  (PDF)

Radiation Risk Management

Space radiation risks are not measured, but predicted. From a practical perspective, it is necessary to address the question of what to do about the probable outcome, once its probability of occurrence has been calculated. The articles in this section discuss the major constraints placed upon space exploration by risk prediction as well as the limitations on the most common conventional means of radiation risk reduction, the use of shielding.

Walter Schimmerling
THREE Chief Editor

  • Radiation Risk Acceptability and Limitations - Francis Cucinotta (PDF)
  • Risk Synthesis: NASA Cancer Risk Models - Francis Cucinotta (HTML)
  • Acceptable Risk - Walter Schimmerling (Article)
  • Radiation Protection - Walter Schimmerling (HTML)
  • Radiation Shielding - Ronald Turner (PDF)
  • The Evolution of Risk Cross Section - Stanley Curtis (PDF)
  • Space Radiation Cancer Risk Projections and Uncertainties - 2012 - Francis Cucinotta, Myung-Hee Y. Kim, Lori J. Chappell (PDF)
  • Probability of Causation for Space Radiation Carcinogenesis following International Space Station, Near Earth Asteroid, and Mars Missions - 2012 - Francis Cucinotta (PDF)
  • Evaluating Shielding Approaches to Reduce Space Radiation Cancer Risks - 2012 - Francis Cucinotta (PDF)

Computer Tools

Computers are an essential way to incorporate the results of physics, chemistry and biological research into the design of experiments, the assessment of their significance, the design of space architectures and missions, and prediction of risk, and the establishment of action levels prior to reaching risk thresholds. This section describes several computational tools available to NASA researchers and provides information on how to obtain instructions for their use and how to access them.

Walter Schimmerling
THREE Chief Editor

  • NASA Space Radiation Program Integrative Risk Model Toolkit - Myung-Hee Y. Kim, Shaowen Hu, Ianik Plante, Artem Ponomarev

    Presented at the NASA HRP IWS 2015, NSRL User’s Group Meeting, January 14, 2015, Galveston, TX

  • NSCR – NASA Space Cancer Risk Integrated Tools (NSCR)1, Web Server Release 1.0 - Francis Cucinotta

    Exposure to solar particle events (SPE) and galactic cosmic rays (GCR) poses cancer risks to astronauts. The NASA Johnson Space Center-Space Radiation Program Element (JSC-SRPE) has developed cancer risk projection code and has evaluated the level of uncertainty that exists for each of the factors (parameters) that are used in the model. The model originated from recommendations of the National Council on Radiation Protection and Measurements (NCRP, 1997; 2000) with revisions from the latest analysis of human radio-epidemiology data. NASA-defined radiation quality factors are formulated with probability distribution functions (PDFs) to represent uncertainties in leukemia and solid cancer risk estimates. The model was reviewed by the National Research Council (NRC) in 2012. Monte-Carlo propagation of uncertainties from different sources is described with PDFs. Models of the space environment and the BRYNTRN and the HZETRN are used to determine organ exposures behind spacecraft shielding. The purpose of the NASA Space Cancer Risk (NSCR) web server is to provide seamless integration of input and output manipulations, which are required for operation of the sub-modules--BRYNTRN, SUMSHIELD, and the Cancer probabilistic response models. The main applications envisioned for NSCR are International Space Station (ISS) missions, and planning for future exploration missions to the moon, near earth objects (NEO), or Mars. In addition, cancer risk estimates for medical diagnostic and aviation radiation exposures are evaluated using similar methods.

    System Requirements

    The NSCR web server has been tested with Google Chrome, Microsoft Internet Explorer (IE) and Mozilla Firefox. For IE the progress of BRYNTRN, SUMSHIELD, and REID calculations cannot be displayed.

    User Selected Environment(s):

    • Galactic Cosmic Rays (GCR)
            Badhwar-O'Neil model
    • Solar Particle Event (SPE)
           Type of energy distribution (Exponential and Weibull)
           Select historical events with pre-defined spectra
    • Space Exploration Missions
           Interplanetary space
           Lunar surface
           Mars surface
           Low Earth Orbit (LEO)

    • The online tools and models are available to authorized users. To request a username and password to access these tools, please contact Dale Ward at the following address:

  • PolyFit: A C++ code for polynomial curve fit with calculation of error bars - Ianik Plante (Article)

    In radiobiology, many dose-response results are modeled using the so-called linear-quadratic (LQ) model, which means that results are modeled as a function of dose D as R(D)=ß01D+ß2D2. The coefficients ß0, ß1 and ß2 are obtained from fitting a series of data points (xi,yi), which is usually done using a least-square method. The LQ and more generally the polynomial fit capability is implemented in many software that analyzes data. However, there are some instances where the fitting needs to be done programmatically. Furthermore, depending on the software used, some features may not be implemented. In this mini-review, I discuss the basis of polynomial fitting, including the calculation of errors on the coefficients and results, use of weighting and fixing the intercept value (the coefficient ß0). A simple C++ code to perform the polynomial curve fitting is also provided. This code should be useful not only in radiobiology but in other fields of science as well.

  • Space Radiation Environment1

    The Badhwar and O'Neill 2010 (BO'10) Galactic Cosmic Ray (GCR) model2 generates a GCR energy spectrum (differential flux versus energy) from 1.0 to 1.0E6 MeV/n for one element (for z=1 to 94). It has been revised to model all balloon and satellite GCR measurements since 1955. This includes the newer 1997-2010 Advanced Composition Explorer (ACE) measurements and spans six solar cycles.

    The code solves the Fokker–Planck equation for given PHI (the solar modulation parameter that describes the current state of the sun's ability to modulate cosmic rays) by propagating the element'(z) Local Interstellar Spectrum (LIS) to one (1) AU.

    This model runs on a pc and generates unshielded GCR energy spectra near earth (~ 1-2 AU, outside the magnetosphere) for elements from hydrogen to plutonium (z=1 to 94). For questions or problems, contact Patrick O'Neill at the Johnson Space Center, Avionic Syst. Div., NASA, Houston, TX 77058, USA.

  • HZETRN2015

    The HZETRN2015 transport code is now available. This latest update includes the same functionalities as the previous release, HZETRN2010, along with several important new features:

    1. 3D transport in user-defined combinatorial geometry or ray-trace geometry.
    2. The pion, muon, and electromagnetic cascade components are included in transport procedures.
    3. Additional options have been added to the cross section module to enable direct access to certain atomic and nuclear cross sections.
    4. The Badhwar-O'Neill 2014 GCR model is fully integrated into the transport module and can be evaluated using mission dates or by specifying a solar modulation parameter.
    5. Options for solar particle event boundary conditions have been expanded to enable user-defined parameters for several historical fitting functions.

    Users may direct questions, bugs, and related issues to
    Instructions on how to access the software are provided below.

    To obtain HZETRN2015 for INDIVIDUAL USE (for example: you will be installing the software on your personal computer and there will be no other users), please provide the following information to

    1. Software User Name:
    2. Home Address: (No P.O. Boxes are allowed)
    3. Home or Cell Phone:
    4. Personal email:
    5. Country of Birth:
    6. Country of Citizenship (If dual – list both):
    7. Reason for Software:

    Note: Please provide your personal address, phone, and email (Do not use your company's information).

    HZETRN2015 cannot be distributed or transmitted to individuals or parties in an embargoed or sanctioned country:
    or to denied parties, specially designated nationals, and entities of concern:

    To obtain HZETRN2015 for BUSINESS PURPOSES (for example, you will be installing the software on a company/university computer or it has company/university use), you will need to visit the NASA Software Release Catalog at The HZETRN2015 software can be found within the website by typing "HZETRN2015" in the search field or directly via the link Once a software request has been made, you will be directed to create an account on the website and fill out a questionnaire that gathers the information needed to create a Software Usage Agreement (SUA). This online system is a little unforgiving, so please take a few minutes to read over the information carefully to ensure your submission is accurate. The following information will be needed to complete the online questionnaire

    1. Company/University Name:
    2. Company/University Address: (No P.O. Boxes are allowed)
    3. Is this a US owned Company:
    4. Software Recipient/User (This is the person the software will be sent to)
      • Full Legal Name
      • Work Address
      • Email Address (Should be company/university email)
      • Phone number
    5. Reason for Software:

    Signatory Authority (The Signatory Authority is someone who can legally bind the company; ie: President/CEO, Administrative Officer, Senior Management)

    1. Full Legal Name
    2. Title
    3. Company Address
    4. Phone
    5. Company Email

    HZETRN2015 cannot be distributed or transmitted to individuals or parties in an embargoed or sanctioned country:
    or to denied parties, specially designated nationals, and entities of concern:

  • Acute Radiation Risk and BRYNTRN Organ Dose (ARRBOD) Projection1

    The NASA Baryon Transport code (BRYNTRN) and the Acute Radiation Risk (ARR) code have been combined into a user friendly Graphical User Interface (GUI) to predict organ doses and prodromal risks for major solar particle events. The ARRBOD GUI is intended for mission planners, radiation shield designers, space operations in the mission, and space biophysics researchers. The ARRBOD GUI will serve as a proof-of-concept example for future integration of other human space applications risk projection models.

  • GCR Event-Based Risk Model (GERMcode)1

    GERMcode allows scientists to model beam line experiments, such as those performed at the NASA Space Radiation Laboratory, utilizing variables for ion type, shielding materials, and sample holders. The software enables experimenters to interpret their data and to estimate the basic physical and biological output of the experiments. The software allows simulation of heavy ion beams including energy loss (LET), nuclear interactions, track structures, and Bragg curves and to integrate biological response models with physical descriptions of heavy ion beams.

    • GCR Event-Based Risk Model (Germcode) – Francis Cucinotta (html)

  • Relativistic Ion Tracks (RITRACKS)1

    RITRACKS simulates the stochastic nature of the energy deposition of relativistic ions. It was developed to use the Monte Carlo technique to simulate a stochastic cascade of biological events. RITRACKS illustrates the biophysical model of ionization and the excitation processes of the ion's track and the electrons liberated by the ion

  • Particle Irradiation Data Ensemble (PIDE)1 - Thomas Friedrich, Michael Scholz

    PIDE is a radiobiological data base compiling more than 800 pairs of in-vitro cell survival experiments after photon and ion irradiation, which were found in about 75 publications. The experiments comprise investigations with both normal and tumor cell lines of human and rodent origin, either synchronized in cell cycle or not. The experiments listed in PIDE furthermore cover various properties of charged particle radiation, i.e. various particle species, LETs and different irradiation conditions such as monoenergetic or within a spread out Bragg peak.

    This data ensemble is convenient to study the relative biological effectiveness (RBE) for clonogenic cell survival as endpoint, or to benchmark RBE predicting models against experimental data. In the data base, the radiosensitivity of the cell lines is parameterized using the linear quadratic model. In the PIDE the experiments are stored in such a way that it is possible to discriminate between RBE relevant experimental factors such as the biological target, radiation quality and delivery techniques.

    GSI shares the PIDE with the research community. The data ensemble is freely available as a file-package after registration from the modeling section of the GSI biophysics homepage:

  • TRiP98 (TReatment PlannIng for Particles)

    TRiP98 is the computational kernel for a treatment planning system used clinically for carbon ion radiotherapy at GSI from 1997 to 2008. It served as a prototype for the commercial Syngo PT code from Siemens, and is now being used as a research prototype at various places. One of its main purposes is sophisticated nonlinear dose optimization and dose calculation, taking into account the relevant physical and radiobiological properties of ion radiation. It achieves computational efficiency by using precalculated tables wherever possible, but also has a numerical-analytical (non-MC) transport code to create the necessary base data sets.

    The transport model in its first phase uses conventional dE/dx tables, such as provided by the LBL Salamon code, but others could be used as well. The ionization potential has been fine-tuned to reproduce the experimental Bragg peak position, which is the most critical quantity in ion-beam radiotherapy, because it has to be predicted with sub-mm precision. For the nuclear part semi-empirical descriptions like those of Silberberg-Tsao are used, but again the cross sections have to be tuned to agree with representative experimental results. In a second phase, lateral spread of the beam (by nuclear or multiple Coulomb interaction) can be added to create a complete pencil beam description plus a large set of particle energy spectra as a function of depth. In actual treatment planning only these tables are used in order to obtain acceptable planning throughput.

    While these codes have not yet been applied to space travel it is easy to imagine how they might be used. Essentially, considering a space craft exposed to GCR as equivalent to being inserted into a computerized tomography device, the dose absorbed by astronauts or their internal organs can be computed efficiently. If RBE or other relevant datasets are used, e.g., late effects rather than clonogenic survival, it should be possible to use TRIP98 components efficiently to generate biological dose distributions relevant for space application.

    For more information consult the online writeup, or contact the principal author,

  • PHITS (Particle and Heavy Ion Transport code System) - Lembit Shiver (PDF)

  • Monte Carlo Transport Codes for use in the Space Radiation Environment - Lawrence Pinsky (PDF)

  • MCNP6 (Monte Carlo N-Particle) Transport Code - Tim Goorley (PDF)

  • Lung Cancer Explorer

    The Lung Cancer Explorer, an open web portal to explore gene expression and clinical associations in lung cancer, was developed at The University of Texas Southwestern Medical Center (partially supported by the NASA funded UT Southwestern Medical Center Lung Cancer NSCOR grant, NNX11AC54G). This database aggregates over 30 public clinically-annotated lung cancer gene expression studies, along with some private data from the University of Texas Southwestern Medical Center, and presents a user-friendly, web-based interface to explore and analyze this data.

  • GEANT4 (“GEometry ANd Tracking”) - Dennis Wright (PDF)

  • FLUKA (FLUctuating KAskade) - Alfredo Ferrari, Lawrence Pinsky (PDF)

  • Cosmic Ray Effects on Micro-Electronics (CREME)

    CREME is a web-based set of tools that allows engineers and scientists to obtain estimates of the ionizing radiation environment in deep space at 1 AU and averaged around any satellite orbit of Earth. It also contains tools to evaluate radiation effects on microelectronics in space. The tools use models of the galactic cosmic ray and solar energetic particle events to generate a description radiation environment in deep space. This description can be modified by an orbit-averaged geomagnetic transmission function and transport through shielding to obtain a description of the environment at any point within a spacecraft. Monte Carlo radiation transport simulations are available to perform a detailed local approximation the ionizing energy deposited in small volumes. The tools can be used to calculate the radiation dose as well as heavy ion and proton-induced single event effect rates using either analytic or Monte Carlo approaches. 


    The On-Line Tool for the Assessment of Radiation in Space (OLTARIS,) is a web-based set of tools and models that allows engineers and scientists to assess the effects of space radiation on spacecraft, habitats, rovers, and spacesuits. The site is intended to be a design tool for those studying the effects of space radiation for current and future missions as well as a research tool for those developing advanced material and shielding concepts.  The tools and models are built around the HZETRN2010 radiation transport code and are primarily focused on human- and electronic-related responses.


    SPENVIS is an ESA operational software developed and maintained at BIRA-IASB since 1996. It provides standardized access to most of the recent models of the hazardous space environment, through a user-friendly Web interface ( The system allows spacecraft engineers to perform a rapid analysis of environmental problems related to natural radiation belts, solar energetic particles, cosmic rays, plasmas, gases, magnetic fields and micro-particles. Various reporting and graphical utilities and extensive help facilities are included to allow engineers with relatively little familiarity to produce reliable results. SPENVIS also contains an active, integrated version of the ECSS Space Environment Standard and access to in-flight data on the space environment. Although SPENVIS in the first place is designed to help spacecraft designers, it is also used by technical universities in their educational programs. In the framework of the ESA Space Situational Awareness Preparatory Programme, SPENVIS is part of the initial set of precursor services of the Space Weather segment. SPENVIS includes several engineering models to assess to effects of the space environment on spacecrafts such as surface and internal charging, energy deposition, solar cell damage and SEU rates.

    The link to the web application is

1Some of these tools have been released for distribution to authorized users. Their status can be determined by checking the Crew and Life Support category in the Tech Tran Software Catalog (or by using its Search function).

2O'Neill, P.M. "Badhwar–O'Neill 2010 Galactic Cosmic Ray Flux Model—Revised." IEEE Transactions on Nuclear Science. 57 (6): 3148–3153 (2010)

3There are some web tools that can be tested inside the NASA firewall: ARRBOD, ARSA, HemoDose, NSCR, NSCR-ISS. If you are a NASA employee and want to know more, contact Dr. Shaowen Hu.