- Email: [email protected]
Monitoring and simulation of the radiation environment for manned and unmanned space missions
Nuclear Physics B (Proc. Suppl.) 172 (2007) 321–323 www.elsevierphysics.com
Monitoring and simulation of the radiation environment for manned and unmanned space missions G.Santina,b, H. Evansa,b, R. Lindberga, P. Nieminena, A. Mohammadzadeha, E. Dalya a
ESA-ESTEC, Space Environments and Effects Analysis Section Keplerlaan 1, 2200 AG Noordwijk, The Netherlands
b
RHEA System SA Louvain-La-Neuve, Belgium
Reliable models of the space radiation environment need precise and up-to-date measurements of the radiation fields in space. The analysis of the potential impact of modelled radiation on evolving space borne devices relies on precise tools for the understanding and the prediction of the basic effects of the particle environment on new technologies. Simulations play a major role in the understanding of the underlying phenomena of the interaction of the particle radiation with the spacecraft devices, lowering costs by complementing experimental tests.
1.
INTRODUCTION
The space radiation environment poses serious problems to the survivability of space systems, which need to be accounted for in the design and operation phases of space missions [1]. Reliable models of the environment itself need precise and up-to-date measurements of the radiation fields in space. In addition, the highly dynamic behaviour of the radiation fields also often imposes to complement models with real-time monitoring. We present recent ESA activities in this area, including electron Van Allen belt analyses and observations of the effect of interplanetary propagation to solar proton events. The analysis of the potential impact of radiation on evolving space borne devices relies on precise tools for the understanding and the prediction of the ` This work was supported by ESA Technology Research Programmes and the ESA Aurora Programme.
0920-5632/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysbps.2007.08.016
basic effects of the particle environment on new technologies [2]. In addition to cumulative effects such as dose, single event effects (SEE) in modern microelectronics are often a major cause of spacecraft failures or anomalies. Simulation can play a major role in the understanding of the underlying phenomena of the interaction of the particle radiation with the spacecraft devices. Even the most complete space qualification ground test procedure for all new components are not able to cover, in energy and species, the entire range of the particle radiation population in space New requirements for the analysis of the radiation biological effects are also arising in the context of increased interest in human exploration initiatives. ESA funded programmes aim at the description of planetary environments with the interaction of solar and cosmic radiation with atmospheres, soils and finally human body.
322
2.
G. Santin et al. / Nuclear Physics B (Proc. Suppl.) 172 (2007) 321–323
GRAS FOR THE SIMULATION RADIATION EFFECTS
OF
The availability of reliable simulation tools can lower space component qualification costs by complementing a more limited set of experimental tests, while still giving enough confidence on the component behaviour in space. Geant4 Radiation Analysis for Space (GRAS) [3] is a Geant4-based tool [4] for the assessment of the impact of radiation to space systems offering many radiation analyses types (including TID, NIEL, fluence, path length, charge deposit, dose equivalent, etc.) in generic 3D geometry models [5]. The range of space radiation sources extends from very low to very high energy, and the interactions with the spacecraft sensitive devices and the shielding structures include both electromagnetic and hadronic processes. A very large subset of the physics models available within Geant4 are included in the GRAS tool, with the aim of giving an almost complete coverage of the main interaction mechanisms for trapped, solar and cosmic radiation in the spacecraft materials. The main requirements for the development of the GRAS tool were flexibility and modularity [6]. The core part of the analysis is constituted by the “analysis modules”, which can be inserted by the user via UI commands to perform the individual analysis tasks. Thanks to the modular design (see Figure 1), the GRAS analysis type capabilities are being easily extended. Advanced users can add new module types by extending or implementing analysis models not existing yet in GRAS: a new analysis class can inherit the functionalities of an existing (object-oriented) GRAS class to quickly add features as a new module type. Recent additions include charge collection models for the simulation of radiation microdosimetry effects in semiconductor devices. Thanks to the flexibility GRAS is used for obtaining a variety of simulation output types for whichever (GDML or C++) 3D geometry model. All analyses can be applied to any user defined set of volumes or surfaces, chosen among those present in the geometry model. Results are saved as scalars (with errors), histograms or “tuples”, also output in simple text format. Users also have the choice of the units for the result output. The tool flexibility avoids the creation of a new tailored C++ Geant4-based application for every new project.
Figure 1. The diagram shows the modular structure of the GRAS tool and the link to the GEANT4 simulation core. Specific analysis modules can evaluate the effects of radiation to humans: “Dose Equivalent” analysis, based on LET quality factors (QF); and “Equivalent Dose” based on the incident particle weights are available in GRAS, with a choice among several factor functions from existing protocols in the literature. The Q(L) relationship between the QF and the LET is implemented in GRAS based on ICRP 60 recommendations [7]. The radiation Weighting Factors (wR) used for “Equivalent Dose” estimates can be chosen from the values adopted in [7] or the re-appraisal of the factors given in ICRP 92 [8]. 3.
SPACE RADIATION MONITORING
ESA activities in the area of environment monitoring include radiation monitor development for near-Earth and interplanetary science and exploration missions. Among the monitors that are being flown at present on ESA missions, the Standard Radiation Environment Monitor (SREM) [9] is a simple low-cost multi-purpose particle detector. Designed by Paul Scherrer Inst., and manufactured by Contraves Space (Switzerland), the monitor has as objectives the support to payloads and systems (alert and “safeing”) and provision of data supporting payload data analysis (e.g. background), investigation of anomalies and “events”, and environment model validation for future missions. The design minimises the impact on host spacecraft in terms of mass, power, commanding, data rate, etc. Data provided by the detectors include time resolved protons and electrons and high DE events with limited angular
G. Santin et al. / Nuclear Physics B (Proc. Suppl.) 172 (2007) 321–323
resolution and spectral information. The instrument drives a network of dosimeters distributed on platform. Ten SREM’s have been manufactured, and four flown so far. 3.1. Solar events near Earth and in interplanetary space In- and post-flight data analysis gives support to the development of new more accurate models of the space radiation environment and its variations at different times and locations. The November 2004 solar event was observed by SREM detectors on 2 spacecraft, INTEGRAL near Earth and ROSETTA in its journey towards the Comet 67 P/Churyumov-Gerasimenko. The spectra and time pattern of the proton fluence presents significant differences at the 2 locations (see Figure 2) showing the impact of the complex phenomena involved in the propagation of solar radiation in the heliosphere. The curves represent raw counts for SREM channels S34 and C1, corresponding respectively to protons with kinetic energy Ep>12.MeV and 43.MeV
4.
CONCLUSIONS
We presented the development and application of the Geant4-based GRAS tool for the support of space missions in the particle radiation environment domain, in the field of radiation effect assessment to systems and space-flight crew. Data were presented from radiation monitors on board ESA spacecraft during a period of intense solar activity, stressing the importance of availability of precise data for the modeling of the space radiation environment for present and future missions. REFERENCES 1.
2.
3.
4.
5.
6.
7.
8. Figure 2. Data provided simultaneously by two SREM instruments located near-Earth (top) and in interplanetary space (bottom) during a solar event show significant differences of spectrum and timepattern.
323
9.
E.J. Daly, “Outlook on space weather effects on spacecraft”, in “Effects of space weather on technology infrastructure”, pages 91-108, Kluwer Academic Publishers, 2004. G. Santin et al., “New Geant4 based simulation tools for space radiation shielding and effects analysis”. Published in Nucl. Phys. B (Proc. Suppl.) vol.125C, pp. 69-74 (2003). G. Santin et al., “GRAS: A general-purpose 3-D modular simulation tool for space environment effects analysis”, IEEE Trans. Nucl. Sci. 52, Issue 6, 2005, pp. 2294 – 2299. S. Agostinelli et al. [GEANT4 Collaboration], "Geant4: a simulation toolkit", Nucl. Instrum. Meth A506, 250 (2003). Geant4 web site: http://cern.ch/geant4 W. Pokorski, R. Chytracek, J. McCormick, G. Santin, “Geometry Description Markup Language and its application specific bindings”, IEEE Trans. Nucl. Sci. 53, Oct 2006. G. Santin, “Space environments and effects analysis for ESA missions”, Nucl. Phys. B (Proc. Suppl.) vol. 150 (2006) “1990 Recommendations of the International Commission on Radiological Protection”, Annals of the ICRP, Vol. 21, No. 1-3, 1991. “Relative biological effectiveness (RBE), quality factor (Q), and radiation weighting factor (wR)”, Annals of the ICRP, Vol. 33, No. 4, 2003. H.D.R.Evans et al., “Results from the ESA SREM Monitors and Comparison with Existing Radiation Belt Models”, Proceedings of COSPAR’06, Beijing, China, 2006.
Monitoring and simulation of the radiation environment for manned and unmanned space missions G.Santina,b, H. Evansa,b, R. Lindberga, P. Nieminena, A. Mohammadzadeha, E. Dalya a
ESA-ESTEC, Space Environments and Effects Analysis Section Keplerlaan 1, 2200 AG Noordwijk, The Netherlands
b
RHEA System SA Louvain-La-Neuve, Belgium
Reliable models of the space radiation environment need precise and up-to-date measurements of the radiation fields in space. The analysis of the potential impact of modelled radiation on evolving space borne devices relies on precise tools for the understanding and the prediction of the basic effects of the particle environment on new technologies. Simulations play a major role in the understanding of the underlying phenomena of the interaction of the particle radiation with the spacecraft devices, lowering costs by complementing experimental tests.
1.
INTRODUCTION
The space radiation environment poses serious problems to the survivability of space systems, which need to be accounted for in the design and operation phases of space missions [1]. Reliable models of the environment itself need precise and up-to-date measurements of the radiation fields in space. In addition, the highly dynamic behaviour of the radiation fields also often imposes to complement models with real-time monitoring. We present recent ESA activities in this area, including electron Van Allen belt analyses and observations of the effect of interplanetary propagation to solar proton events. The analysis of the potential impact of radiation on evolving space borne devices relies on precise tools for the understanding and the prediction of the ` This work was supported by ESA Technology Research Programmes and the ESA Aurora Programme.
0920-5632/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysbps.2007.08.016
basic effects of the particle environment on new technologies [2]. In addition to cumulative effects such as dose, single event effects (SEE) in modern microelectronics are often a major cause of spacecraft failures or anomalies. Simulation can play a major role in the understanding of the underlying phenomena of the interaction of the particle radiation with the spacecraft devices. Even the most complete space qualification ground test procedure for all new components are not able to cover, in energy and species, the entire range of the particle radiation population in space New requirements for the analysis of the radiation biological effects are also arising in the context of increased interest in human exploration initiatives. ESA funded programmes aim at the description of planetary environments with the interaction of solar and cosmic radiation with atmospheres, soils and finally human body.
322
2.
G. Santin et al. / Nuclear Physics B (Proc. Suppl.) 172 (2007) 321–323
GRAS FOR THE SIMULATION RADIATION EFFECTS
OF
The availability of reliable simulation tools can lower space component qualification costs by complementing a more limited set of experimental tests, while still giving enough confidence on the component behaviour in space. Geant4 Radiation Analysis for Space (GRAS) [3] is a Geant4-based tool [4] for the assessment of the impact of radiation to space systems offering many radiation analyses types (including TID, NIEL, fluence, path length, charge deposit, dose equivalent, etc.) in generic 3D geometry models [5]. The range of space radiation sources extends from very low to very high energy, and the interactions with the spacecraft sensitive devices and the shielding structures include both electromagnetic and hadronic processes. A very large subset of the physics models available within Geant4 are included in the GRAS tool, with the aim of giving an almost complete coverage of the main interaction mechanisms for trapped, solar and cosmic radiation in the spacecraft materials. The main requirements for the development of the GRAS tool were flexibility and modularity [6]. The core part of the analysis is constituted by the “analysis modules”, which can be inserted by the user via UI commands to perform the individual analysis tasks. Thanks to the modular design (see Figure 1), the GRAS analysis type capabilities are being easily extended. Advanced users can add new module types by extending or implementing analysis models not existing yet in GRAS: a new analysis class can inherit the functionalities of an existing (object-oriented) GRAS class to quickly add features as a new module type. Recent additions include charge collection models for the simulation of radiation microdosimetry effects in semiconductor devices. Thanks to the flexibility GRAS is used for obtaining a variety of simulation output types for whichever (GDML or C++) 3D geometry model. All analyses can be applied to any user defined set of volumes or surfaces, chosen among those present in the geometry model. Results are saved as scalars (with errors), histograms or “tuples”, also output in simple text format. Users also have the choice of the units for the result output. The tool flexibility avoids the creation of a new tailored C++ Geant4-based application for every new project.
Figure 1. The diagram shows the modular structure of the GRAS tool and the link to the GEANT4 simulation core. Specific analysis modules can evaluate the effects of radiation to humans: “Dose Equivalent” analysis, based on LET quality factors (QF); and “Equivalent Dose” based on the incident particle weights are available in GRAS, with a choice among several factor functions from existing protocols in the literature. The Q(L) relationship between the QF and the LET is implemented in GRAS based on ICRP 60 recommendations [7]. The radiation Weighting Factors (wR) used for “Equivalent Dose” estimates can be chosen from the values adopted in [7] or the re-appraisal of the factors given in ICRP 92 [8]. 3.
SPACE RADIATION MONITORING
ESA activities in the area of environment monitoring include radiation monitor development for near-Earth and interplanetary science and exploration missions. Among the monitors that are being flown at present on ESA missions, the Standard Radiation Environment Monitor (SREM) [9] is a simple low-cost multi-purpose particle detector. Designed by Paul Scherrer Inst., and manufactured by Contraves Space (Switzerland), the monitor has as objectives the support to payloads and systems (alert and “safeing”) and provision of data supporting payload data analysis (e.g. background), investigation of anomalies and “events”, and environment model validation for future missions. The design minimises the impact on host spacecraft in terms of mass, power, commanding, data rate, etc. Data provided by the detectors include time resolved protons and electrons and high DE events with limited angular
G. Santin et al. / Nuclear Physics B (Proc. Suppl.) 172 (2007) 321–323
resolution and spectral information. The instrument drives a network of dosimeters distributed on platform. Ten SREM’s have been manufactured, and four flown so far. 3.1. Solar events near Earth and in interplanetary space In- and post-flight data analysis gives support to the development of new more accurate models of the space radiation environment and its variations at different times and locations. The November 2004 solar event was observed by SREM detectors on 2 spacecraft, INTEGRAL near Earth and ROSETTA in its journey towards the Comet 67 P/Churyumov-Gerasimenko. The spectra and time pattern of the proton fluence presents significant differences at the 2 locations (see Figure 2) showing the impact of the complex phenomena involved in the propagation of solar radiation in the heliosphere. The curves represent raw counts for SREM channels S34 and C1, corresponding respectively to protons with kinetic energy Ep>12.MeV and 43.MeV
4.
CONCLUSIONS
We presented the development and application of the Geant4-based GRAS tool for the support of space missions in the particle radiation environment domain, in the field of radiation effect assessment to systems and space-flight crew. Data were presented from radiation monitors on board ESA spacecraft during a period of intense solar activity, stressing the importance of availability of precise data for the modeling of the space radiation environment for present and future missions. REFERENCES 1.
2.
3.
4.
5.
6.
7.
8. Figure 2. Data provided simultaneously by two SREM instruments located near-Earth (top) and in interplanetary space (bottom) during a solar event show significant differences of spectrum and timepattern.
323
9.
E.J. Daly, “Outlook on space weather effects on spacecraft”, in “Effects of space weather on technology infrastructure”, pages 91-108, Kluwer Academic Publishers, 2004. G. Santin et al., “New Geant4 based simulation tools for space radiation shielding and effects analysis”. Published in Nucl. Phys. B (Proc. Suppl.) vol.125C, pp. 69-74 (2003). G. Santin et al., “GRAS: A general-purpose 3-D modular simulation tool for space environment effects analysis”, IEEE Trans. Nucl. Sci. 52, Issue 6, 2005, pp. 2294 – 2299. S. Agostinelli et al. [GEANT4 Collaboration], "Geant4: a simulation toolkit", Nucl. Instrum. Meth A506, 250 (2003). Geant4 web site: http://cern.ch/geant4 W. Pokorski, R. Chytracek, J. McCormick, G. Santin, “Geometry Description Markup Language and its application specific bindings”, IEEE Trans. Nucl. Sci. 53, Oct 2006. G. Santin, “Space environments and effects analysis for ESA missions”, Nucl. Phys. B (Proc. Suppl.) vol. 150 (2006) “1990 Recommendations of the International Commission on Radiological Protection”, Annals of the ICRP, Vol. 21, No. 1-3, 1991. “Relative biological effectiveness (RBE), quality factor (Q), and radiation weighting factor (wR)”, Annals of the ICRP, Vol. 33, No. 4, 2003. H.D.R.Evans et al., “Results from the ESA SREM Monitors and Comparison with Existing Radiation Belt Models”, Proceedings of COSPAR’06, Beijing, China, 2006.