ArticlePDF Available

Radiation environment investigations during ExoMars missions to Mars - Objectives, experiments and instrumentation

Authors:

Abstract and Figures

Deep space manned missions are already a near future of astronautics. Radiation risk on such a long-duration journey appears to be one of the basic factors in planning and designing the mission. The paper relates to the scientific objectives and experiments for investigation of the radiation environment to be carried out during the ExoMars 2016 and 2018 joint missions of the European Space Agency (ESA) and the Federal Space Agency of Russia (Roscosmos) to Mars. The following topics are described: 1) The charged particle telescope and the experiment Liulin-MO for measuring the radiation environment on board the ExoMars 2016 Trace Gas Orbiter satellite as a part of the Fine Resolution Epithermal Neutron Detector (FREND) and 2) Liulin-ML experiment and in- strument for investigating the radiation environment on Mars as a part of the active detector of neutrons and gamma rays (ADRON) on the Russian surface platform for ExoMars 2018 mission. Liulin detectors will be used in combina- tion with the neutron detectors to study the radiation conditions both from charged particles and neutrons during the cruise phase, in Mars orbit and on the surface of Mars.
Content may be subject to copyright.
Доклади на Българската академия на науките
Comptes rendus de l’Acad´emie bulgare des Sciences
Tome 68, No 4, 2015
SCIENCES COSMIQUES
Syst`eme solaire
RADIATION ENVIRONMENT INVESTIGATIONS DURING
EXOMARS MISSIONS TO MARS – OBJECTIVES,
EXPERIMENTS AND INSTRUMENTATION
J. Semkova, T. Dachev, St. Maltchev, B. Tomov, Yu. Matviichuk,
P. Dimitrov, R. Koleva, I. Mitrofanov, A. Malakhov,
M. Mokrousov, A. Sanin, M. Litvak, A. Kozyrev,
V. Tretyakov, D. Golovin, S. Nikiforov, A. Vostrukhin,
F. Fedosov, N. Grebennikova, V. Benghin∗∗ , V. Shurshakov∗∗
(Submitted by Corresponding Member P. Velinov on March 21, 2015)
Abstract
Deep space manned missions are already a near future of astronautics.
Radiation risk on such a long-duration journey appears to be one of the basic
factors in planning and designing the mission. The paper relates to the scientific
objectives and experiments for investigation of the radiation environment to be
carried out during the ExoMars 2016 and 2018 joint missions of the European
Space Agency (ESA) and the Federal Space Agency of Russia (Roscosmos) to
Mars. The following topics are described: 1) The charged particle telescope and
the experiment Liulin-MO for measuring the radiation environment on board
the ExoMars 2016 Trace Gas Orbiter satellite as a part of the Fine Resolution
Epithermal Neutron Detector (FREND) and 2) Liulin-ML experiment and in-
strument for investigating the radiation environment on Mars as a part of the
active detector of neutrons and gamma rays (ADRON) on the Russian surface
platform for ExoMars 2018 mission. Liulin detectors will be used in combina-
tion with the neutron detectors to study the radiation conditions both from
charged particles and neutrons during the cruise phase, in Mars orbit and on
the surface of Mars.
Key words: space radiation, radiation risk, space radiation measure-
ments, interplanetary missions, ExoMars
This work is partly supported by Contracts 503/2-13 and 63/4-14 between SRTI, Bulgarian
Academy of Sciences, and SRI, Russian Academy of Sciences.
485
1. Introduction. The deep space manned missions are already a near future
of astronautics. Radiation risk on such a long-duration journey, a great part of
which will take place in the interplanetary space, appears to be one of the basic
factors in planning and designing the mission.
The estimation of the radiation effects for a long-duration manned space
mission requires three distinct procedures: i) Knowledge and modelling of the
particle radiation environment; ii) Calculation of primary and secondary particle
transport through shielding materials; and iii) Assessment of the biological effect
of the dose.
1.1. Sources of ionizing radiation in the interplanetary space. The
radiation field in interplanetary space is complex, composed of galactic cosmic
rays (GCR), solar energetic particles (SEP), and secondary radiation produced
in the shielding materials of the spacecraft and in the biological objects.
The GCR-charged particles that originate from sources beyond the Solar
System are the dominant radiation component in the interplanetary radiation
environment. GCR represent a continuous radiation source and they are the most
penetrating among the major types of ionizing radiation [1]. The distribution of
GCR is believed to be isotropic throughout the interstellar and interplanetary
space. The energies of GCR particles can reach 1020 eV/nucleon. Most of the
deleterious effects with regard to health produced by this radiation are associated
with nuclei in the energy range from several hundred MeV/nucleon to a few
GeV/nucleon. The flux and spectra of those particles show modulation that anti-
correlate with the solar activity. The GCR spectrum consists of 98% protons
and heavier ions (baryon component) and 2% electrons and positrons (lepton
component). The baryon component is composed of 87% protons, 12% helium
ions (alpha particles) and 1% heavy ions [2]. The highly energetic particles in the
heavy ion component, typically referred to as high Z and energy (HZE) particles,
play a particularly important role in space dosimetry [3] and affect strongly the
biological objects and humans in space [4]. HZE particles, especially iron, possess
high linear energy transfer (LET) and are highly penetrating, which gives them
a large potential for radiobiological damage [5]. The average dose rate from
GCR in the interplanetary space measured by the RADOM instrument on the
Chandrayaan-1 satellite [6] during low solar activity was 12–13 µGy h1.
Solar energetic particles (SEP) are randomly distributed events, but they
may deliver very high doses over short periods and that is why they could be
associated with the lethal equivalent doses. The SEP are mainly produced by
solar flares, sudden sporadic eruptions of the Sun chromosphere. High fluxes of
charged particles (mostly protons, some helium and heavier ions) with energies up
to several GeV and intensity up to 104particle cm2s1sr1are emitted. The
time profile of a typical SEP event starts with a rapid increase in flux, reaching
a peak in minutes to hours. Although SEPs are more likely to occur around
solar maximum, such events are at present unpredictable with regard to their
486 J. Semkova, T. Dachev, St. Maltchev et al.
times of occurrence and it cannot be assumed that SEPs will not occur under
solar minimum. The most intense solar proton fluencies observed were those in
August 1972 and October 1989. The flare containing the largest peak flux of
highly penetrating particles was in February 1956 [7–10]. On this basis the so-
called worst-case flare is composed, which is thought to occur once a century, but
statistics are extremely poor.
1.2. Radiation environment on Mars. The radiation environment on
the surface of Mars is much harsher than that on the surface of the Earth for
two reasons: Mars lacks a global magnetic field to deflect energetic GCR and
SEP, and the Martian atmosphere is much thinner (<1%) than that of Earth,
providing little shielding against the high-energy particles that are incident at
the top of its atmosphere. Both GCRs and SEPs interact with the atmosphere
and, if energetic enough, penetrate into the Martian soil, or regolith, where they
produce secondary particles (including neutrons and γ-rays) that contribute to
the complex radiation environment on the Martian surface.
The cosmic rays produce ionization in the ionosphere, atmosphere, hydro-
sphere, cryosphere and lithosphere of the planets [7–10]. The contribution of
cosmic rays to ionization of the outer planetary ionospheres and atmospheres
increases with the increment of the planetary distances from the Sun.
2. Implications for future human missions to Mars. The currently
adopted NASA ionizing radiation exposure limits allow for astronauts a maximum
annual dose of 0.5 Sv to the blood-forming organs (BFO) [11]. The Russian
standards for manned space missions allow also 0.5 Sv a year, but not more
than 1 Sv for the cosmonaut’s career [12]. The recommended ESA and Canadian
astronaut’s career dose limit is also 1 Sv.
To prepare future human exploration of Mars transport models developed
in ([13–17] and references therein) are used for prediction of the particle flux,
absorbed dose, dose equivalent and ionization by GCR and SEPs.
Model estimations show that (see [18]): i) behind relatively thin shielding
the annual dose equivalent to the BFO from GCR is larger than the annual
limit of 0.5 Sv/year; ii) the dose equivalent is a slowly decreasing function of the
shield thickness. As it is pointed out in [18] the uncertainties and the possible
inaccuracies involved in the calculations could result in a potential shield mass
increase by up to a factor of 4. If the exposure is underestimated by a factor of
2, then the shield mass must be increased by an order of magnitude.
Model calculations [19] give a dose rate of about 0.42 Sv h1to the unshielded
BFO for a standard solar proton event and up to 0.70 Sv h1for the worst-case
solar proton event. Under these estimations the necessity of effective shielding is
more than evident. Shielding against solar energetic particles is, at first glance,
simpler than against GCR. However the benefit of less penetration of the flare
particles because of their softer spectrum is offset to a large degree by their high
intensity. In addition, solar energetic particles also produce secondaries, which
Compt. rend. Acad. bulg. Sci., 68, No 4, 2015 487
build up in the shielding materials. In particular the commonly used aluminum
proves to be an insufficiently effective shielding material [7–10].
GCR and SEP events affect the evolution of the climate of Mars, the op-
eration of satellites, and the human exploration of the planet. They can affect
the chemistry on the surface. The energetic inputs also have an impact on the
planetary atmosphere evolution by modifying the escape rates and the chemistry
of the upper atmosphere (see [17] and references therein). The determination of
the Martian surface and sub-surface radiation environment is an ongoing effort
that started with numerical simulations [20,21 ].
Present calculations with the available models show that radiation doses
expected on manned missions to Mars can easily exceed the suggested allowed
doses [16], but we must keep in mind that these estimations bear a lot of uncer-
tainties. Validation of the radiation model predictions available must be secured
before any human mission to Mars is undertaken [22]. Therefore experimen-
tal measurements of radiation environment characteristics on unmanned missions
like ExoMars are of a great importance for the future planning of manned mission
in the interplanetary space and on the surface of Mars.
The most recent investigations during the sojourn to Mars and on Mars
surface performed aboard of NASA Mars Science Laboratory (MSL, Curiosity) by
RAD instrument estimate a total mission dose equivalent of 1.01 Sv for a round
trip Mars surface mission with 180 days (each way) cruise, and 500 days on the
Martian surface for the 2012–2013 weak solar maximum [23,24 ]. The bigger part
of that dose (662 ±108 mSv), which approaches two-thirds of the career exposure
limit recognized at NASA to carry a 3% increased risk of fatal cancer at the
upper 95% confidence level, would be accumulated during the cruise phase. That
dose is also two-thirds of the career exposure limit recognized at Russia, ESA and
Canada. It was noted that only about 5.4% of the contribution to the estimated
total dose equivalent from both GCR and SEP events of 466 ±84 mSv during the
253 days MSL’s cruise to Mars was due to SEPs and it was surmised (given the
relatively low activity profile of solar cycle 24) that the SEP contribution could
have been many times larger had it been measured in a different time frame.
Since 1989 the Liulin type dosemeters-spectrometers have been conducting
measurements of the radiation environment characteristics on board a number of
manned and unmanned spacecrafts in low Earth orbits or in the interplanetary
space [25]. New Liulin type instrumentation will be used for radiation investiga-
tions during the upcoming ExoMars missions to Mars.
3. ExoMars mission. ExoMars is a joint investigation of Mars to be car-
ried out by ESA and Roscosmos that has two launches foreseen, in 2016 and
2018. Establishing if life ever existed on Mars is one of the outstanding scientific
questions of our time. To address this important goal the ExoMars programme
has been established to investigate the Martian environment and to demonstrate
new technologies paving the way for a future Mars sample return mission in
488 J. Semkova, T. Dachev, St. Maltchev et al.
the 2020’s (http://exploration.esa.int/mars/46048-programme-overview).
Planned for launch in 2016, its first element, the Trace Gas Orbiter (TGO) satel-
lite, will spend at least one Martian year orbiting the planet.
Two dosemeters and dosemetric experiments are envisaged for the ExoMars
mission. The first one is the charged particle telescope and the experiment Liulin-
MO for measurement the radiation environment on board the ExoMars 2016
TGO. Liulin-MO is a part of the Fine Resolution Epithermal Neutron Detector
(FREND) on TGO. FREND instrument will measure thermal, epithermal and
high energy neutrons with energies ranging up to 10 MeV, whose variations are
an excellent signature of H bearing substances presence in the Mars regolith at
up to 1 m depth (http://l503.iki.rssi.ru/FREND-en.html). The FREND’s
dosemeter module Liulin-MO is another important part of the system providing
information for the radiation environment during the cruise stage and in Mars’
orbit. The second envisaged experiment is the Liulin-ML experiment for inves-
tigation of the radiation environment on Mars surface. The experiment will be
conducted with the Liulin-ML dosemeter as a part of the active detector of neu-
trons and gamma rays (ADRON) on the Russian surface platform for ExoMars
2018 mission.
4. Liulin-MO and Liulin-ML scientific objectives. The main goal of
the Liulin-MO and Liulin-MO dosemetric experiments is investigation of the ra-
diation conditions in the heliosphere at distances from 1 to 1.5 AU from the Sun
and on Mars. More detailed objectives are to provide during the cruise phase, in
Mars orbit and on Mars surface:
Measurements of the energy deposition spectra, dose rate and particle flux
that allow calculation of the absorbed dose D. Measurements of the LET
spectra in silicon, that allow assessment of LET in water LET(H2O) and
then calculation of the radiation quality factor Qaccording to the Q(L)
relationship given in ICRP-60 [26], where Lstays for LET:
(1) Q=ZQ(L)D(L)dL/D.
Q(L) is related functionally to the unrestricted LET or LET(H2O) of a
given radiation. The quality factor (Q) describes the different biological ef-
fectiveness of the various radiation types. The biologically significant dose
equivalent His obtained as the absorbed dose is weighted by the corre-
sponding quality factor H=D×Q.
Estimate the contribution of electrons, protons, heavier ions of GCR and
SEP as well as of secondary charged particles and γradiation in the ab-
sorbed dose and the dose equivalent composition.
Investigate the journal and seasonal variations of the radiation characteris-
tics on Mars’ surface.
Compt. rend. Acad. bulg. Sci., 68, No 4, 2015 489
The data from Liulin-MO on TGO and Liulin-ML on the ExoMars 2018
surface platform will allow comparison of the orbital and surface Mars radiation
conditions.
The combined data from the dosemeters and neutron detectors of FREND
and ADRON will allow assessment of both the charged particle and the neutron
fluxes and doses over broad energy ranges during periods of quiet Sun and during
SEP events.
Data obtained will serve for verification and benchmarking of the radiation
environment models and assessment of the radiation risk to the crew members of
future exploratory flights.
An additional goal of the Liulin-MO and Liulin-ML experiments is to increase
the accuracy of the neutron measurements by providing information about radi-
ation fluctuations from charged particles that can have an impact on the signals
from the neutron detectors of the FREND and ADRON instruments.
5. Liulin-MO and Liulin-ML description. The Liulin-MO flight and
spare models have been developed and space flight qualified. Liulin-MO is a fur-
ther development of the Liulin-5 and Liulin-Phobos particle telescopes already
flown in space [25, 27–30]. The Liulin-MO particle telescope contains two dosemet-
ric telescopes – D1&D2, and D3&D4 arranged at two perpendicular directions.
The functional diagram of the instrument is shown in Fig. 1. Every pair of the
dosemetric telescopes consists of two 300 µm thick, 20 ×10 mm area Si PIN pho-
todiodes. The detectors D1 to D4, the charge-sensitive preamplifiers – shaping
amplifiers CSA1 to CSA4, the threshold discriminators and the voltage bias cir-
cuits are mounted in a separate detector’s volume inside the box of the Liulin-MO
instrument and are connected to printed circuit boards that contain pulse height
Fig. 1. Functional diagram of Liulin-MO particle telescope
490 J. Semkova, T. Dachev, St. Maltchev et al.
Fig. 2. Block diagram of Liulin-MO
analysis circuits, DC-DC converters, microcontrolers, and interfaces to FREND.
The entire package Liulin-MO has a mass of 0.7 kg and consumes 2.2 W. All
major units of Liulin-MO are duplicated in order to increase the reliability of
the dosemeter. The block diagram is shown in Fig. 2. All detectors D1 to D4
and their electronics, one microcontroler MC1 or MC2 and one power supply
unit operate at every moment. The picture of the FREND accommodation on
the TGO (Credit: Thales Alenia Space – France http://exploration.esa.int/
mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2217) is shown
in Fig. 3A. FREND instrument with mounted on it Liulin-MO is shown in
Fig. 3B. The external view of Liulin-MO is shown in Fig. 3C.
The main measured parameters are the amplitudes of the voltage pulses
at the CSA1–CSA4 outputs (see Fig. 1). The amplitude of a voltage pulse is
proportional to the energy deposited in the corresponding detector by a particle
or a photon crossing the detector, and to the respective dose. By an 8-bit ADC
these amplitudes are digitized and organized in a deposited 256 channels energy
spectrum for every one of the detectors.
The gains of Liulin-MO preamplifiers CSA1 to CSA4 are a compromise be-
tween the conflicting goals of measuring gamma rays, electrons and high-energy
protons (which have very low LET and hence require high gains) and covering the
HZE spectrum (which requires low gains to measure highly ionizing particles such
as iron). As a result of the compromise one of the detectors in every telescope
measures and provides the energy deposition spectrum in the range 0.1–18 MeV
(detectors D2 and D3), and the other in the range 0.4–190 MeV (detectors D1
and D4). The energy deposition spectra of D2 in the range 0.1–18 MeV and
of D1 in the range 18.1–190 MeV are later summarized and used to obtain the
energy deposition spectrum in the direction of D1–D2. The same procedure is
used to obtain the energy deposition spectrum in the direction of D3–D4. In
that way each dosemetric telescope provides data in the energy deposition range
0.1–190 MeV.
Compt. rend. Acad. bulg. Sci., 68, No 4, 2015 491
Fig. 3. A) FREND accommodation on the TGO (Credit: Thales Alenia Space – France http://
exploration.esa.int/mars/48523-trace-gas-orbiter-instruments/?fbodylongid=2217);
B) the FREND instrument with Liulin-MO mounted on it; C) external view of Liulin-MO
A coincidence technique for the associated with every dosemetric telescope
electric signals is applied to obtain the linear energy transfer (LET). The energy
deposition spectra measured in D1 and D2 detectors in coincidence mode are
recorded separately and used to obtain the LET spectrum in the direction of D1–
D2. That LET spectrum consists of low and high LET parts. The low LET part
is obtained from the D2 coincidence spectrum in energy range 0.1–18 MeV and
the high LET part is obtained from the D1 coincidence spectrum in energy range
18.1–190 MeV. Similarly the energy deposition spectra measured in the D3 and
D4 detectors in coincidence mode are recorded separately and used to obtain the
LET spectrum in the perpendicular D3–D4 direction. In addition the instrument
measures the energy deposition spectrum in D3 in coincidence with D2, allowing
492 J. Semkova, T. Dachev, St. Maltchev et al.
estimation of the dose rate and particle flux in the D3–D2 direction as well. In
that way the output parameters of Liulin-MO are provided simultaneously for
three directions.
The energy deposition is converted to energy lost per unit of path length
(dE/dx) in silicon as:
(2) dEi/dx =ELi/hD,
where dEi/dx (keV µm1) is the energy lost per unit of path length in silicon
in channel i,ELi(keV) is the energy deposition in channel i,hD(µm) is the
thickness of the corresponding detector.
A constant factor is applied to relate dE/dx in silicon to LET in water. Ap-
plying the same average value of the ratio dE/dx in silicon and LET in water
of 1.6, with an associated uncertainty of ±15% for GCRs like for RAD instru-
ment [23], LET for water LET (H2O) is then found by the relation:
(3) LET (H2O) = dE/dx
1.6.
By definition the dose D(Gy) is the energy in Joule deposited in 1 kg of
matter. The absorbed dose in a silicon detector DSi (Gy) is calculated by dividing
the summarized energy deposition in the spectrum in Joules to the mass of the
detector in kilograms:
(4) DSi =
256
X
i=1
(ELi)/MD =
256
X
i=1
(niAi/k)/MD =k1
256
X
i=1
(nii)/MD,
where ELiis the energy deposition in channel iin Joule, MD is the mass of
the detector in kg. The energy deposition in MeV is proportional to the voltage
amplitude Aiof the pulses in channel iand respectively to the spectral channel
number i:ELi(MeV) = niAi(V)/k (V MeV1), where niis the number of
pulses in channel i,k(V MeV1) is a coefficient dependent on the preamplifier’s
sensitivity. k1 (J) is a coefficient converting the spectral channel number to the
energy deposited by a single particle or a photon.
The values
256
P
i=1
niand
256
P
i=1
niiproportional to the flux and to the dose are
calculated for each detector from the corresponding energy deposition spectrum
measured for a given time and provided in the Liulin-MO output data.
The parameters provided by Liulin-MO are: absorbed dose rate in the range
107–0.1 Gy h1; particle flux in the range 0–104particle cm2s1; energy de-
position spectrum in the range 0.1–190 MeV; LET(H2O) spectrum in the range
0.2–395 keV µm1. The above parameters are provided for three directions si-
multaneously. The dose rates and the fluxes are resolved every minute, while
Compt. rend. Acad. bulg. Sci., 68, No 4, 2015 493
the energy deposition spectra and the LET spectra are resolved every hour. The
telemetry data rate is 250 kByte/day.
The dosemeter Liulin-ML for ExoMars 2018 will be similar to Liulin-MO
dosemeter developed for ExoMars 2016 mission.
6. Liulin-MO calibration. The Liulin-MO dosemeter has been electroni-
cally calibrated using electrical test pulses through a small capacitor (1–2 pF) to
inject a test charge into the input of each CSA. The amplitude Aiof the voltage
pulses at the output of each CSA was measured and the corresponding spectral
channel iwas obtained. In that way the value of k1 in (4) that converts the
spectral channel number to the deposited energy by a single particle or a photon
was obtained for each of the Liulin-MO detectors.
Liulin-MO has been physically calibrated using standard γ-sources. Figure 4
presents the calibration diagram that shows the dependence of dose rate measure-
ments in detector D3 (in relative units) on the dose rate of γ-sources used (dose
rate is estimated at the centre of the parallelepiped formed by all four detectors).
The linear approximation of that dependence is also shown. Those calibrations
confirm the large dynamic ranges of the flux (up to 104particle cm2s1) and the
dose rate (107–0.1 Gy h1) measurements that allow Liulin-MO to measure the
fluxes and dose rates both of the relatively low-intensity GCR and the occasional
high-intensity powerful SEP events. The instrument has also enough sensitivity
to measure the natural radiation background on the Earth surface that is used to
control the proper operation of its detectors during the pre-flight tests.
7. Conclusions. A new charged particle telescope Liulin-MO for measuring
the radiation environment on board the ExoMars 2016 Trace Gas Orbiter satellite
as a part of the Fine Resolution Epithermal Neutron Detector (FREND) has been
Fig. 4. Calibration curve of dose rate measurements in detector
D3. The measured dose is marked with circles. Dashed line with
triangles is the linear approximation
494 J. Semkova, T. Dachev, St. Maltchev et al.
developed, calibrated and space flight qualified. The dynamic range of the LET
spectrum (in H2O) measured by Liulin-MO 0.2–395 keV µm1allows for the
assessment of the contribution to the absorbed dose and to the dose equivalent
of the electrons, protons and the high energy particles in the heavy ion cosmic
component including highly ionizing particles such as iron, and the secondary
charged particles and gamma radiation. The large dynamic ranges of the flux
(up to 104particle cm2s1) and the dose rate measurements 107–0.1 Gy h1
allows Liulin-MO to measure the fluxes and dose rates both of the relatively
low-intensity GCR and the occasional high-intensity powerful SEP events. The
launch of the ExoMars mission to Mars is planned for the beginning of 2016. A
similar Liulin-ML experiment and instrument for investigation of the radiation
environment on Mars as a part of the active detector of neutrons and gamma
rays (ADRON) on the Russian surface platform is proposed for ExoMars 2018
mission. The charged particle telescopes will be used in combination with the
neutron detectors of FREND and ADRON to study the radiation conditions
from charged particles, neutrons and gamma rays during the cruise phase, in
Mars orbit and on the surface of Mars.
REFERENCES
[1]Mewaldt R. A. (1996) http://www.srl.caltech.edu/personnel/dick/cos_
encyc.html.
[2]Simpson J. A. (1983) In: NATO ASI Series C: Mathematical and Physical Sciences
(ed. M. M. Shapiro), 107, Dordrecht, Reidel.
[3]Benton E. R, E. V. Benton (2001) Nucl. Instrum. and Methods in Physics
Research, B, 184 No 1–2, 255–294.
[4]Horneck G. (1994) Acta Astronautica, 32, 749–755.
[5]Kim M.-H. Y. et al. (2011) Acta Astronaut. 68, No 7–8, 747–759.
[6]Dachev Ts. P. et al. (2011) Adv. Space Res., 48, No 5, 779–791, doi: 10.1016/
j.asr.2011.05.009.
[7]Buchvarova M., P. I. Y. Velinov (2010) Adv. Space Res., 45, No 8, 1026-1034.
[8]Gronoff G. et al. (2011) Astronomy and Astrophysics, 529, No 5, A143–A146.
[9]Mishev A. et al. (2012) Atmos. Solar-Terr. Phys., 89, 1–7.
[10]Mishev A., P. I. Y. Velinov (2014) Atmos. Solar-Terr. Phys., 120, No 12, 111–
120.
[11]Cucinotta F. A. et al. (2011) NASA Tech. Paper 2011-216155. NASA Scientific
and Technical Information (STI) Program, Hampton, VA.
[12] Methodical instructions MU 2.6.1.44-03-2004 (2004) Limiting the exposure of as-
tronauts during spaceflight near Earth. Moscow, Federal Office “Medbioextrem”
(in Russian).
[13]Wilson J. W. et al. (1991) NASA TP-3146.
[14]Slaba T. C. et al. J. Comput. Phys., 229, No 24, 9397–9417.
[15]Schwadron N. et al. (2010) Space Weather 8, S00E04.
6Compt. rend. Acad. bulg. Sci., 68, No 4, 2015 495
[16]McKenna-Lawlor S. et al. (2012) Planetary and Space Science, 63–64, 123–132.
[17]Gronoff G. et al. (2015) Adv. Space Res., 55, 1799–1805.
[18]Wilson J. W. et al. (1991) NASA Reference Publ. 1257, Ch. 11, 420.
[19]Letaw J. R., S. Clerwater (1986) SCC Report 86-02.
[20]Velinov P. I. Y., L. Mateev (1991) Compt. rend. Acad. bulg. Sci., 44, No 1,
31–34.
[21]De Angelis et al. (2007) Nucl. Phys., B166, 184–202.
[22]McKenna-Lawlor S. et al. (2015) Acta Astronautica, 109, 182–193.
[23]Zeitlin C. et al. (2013) Science, 340, 1080–1084, doi: 10.1126/science.1235989.
[24]Hassler D. M et al. (2014) Science, 343, 1244797-1-1244797-6, doi: 10.1126/
science.1244797.
[25]Dachev T. P. et al. (2015) Life Sciences in Space Research, 4, 92–114.
[26] International Commission on Radiological Protection (1991) ICRP Report No 60.
Oxford, Pergamon Press.
[27]Semkova J. (2007) Compt. rend. Acad. bulg. Sci., 60, No 9, 957–966.
[28]Semkova J. et al. (2008) Proc. Int. Conf. Fundamental Space Research, Sunny
Beach, Bulgaria, 23–28 Sept. 2008, 351–354, ISBN 978-954-322-316-9.
[29]Semkova J. et al. (2009) Proc. Int. Conf. Fundamental Space Research, Suppl.
Compt. rend. Acad. bulg. Sci., 215–218, ISBN 978-954-322-316-9.
[30]Semkova J. et al. (2010) Adv. Space Res., 45, No 7, 858–865, doi: 10.1016/
j.asr.2009.08.027.
Space Research and Technology Institute
Bulgarian Academy of Sciences
e-mail:jsemkova@stil.bas.bg
Space Research Institute
Russian Academy of Sciences
Moscow, Russia
e-mail:malakhov@iki.rssi.ru
∗∗State Scientific Center of Russian Federation
Institute of Biomedical Problems
Russian Academy of Sciences
Moscow, Russia
e-mail:v benghin@mail.ru
496 J. Semkova, T. Dachev, St. Maltchev et al.
... The ExoMars TGO mission represents a unique opportunity to conduct measurements of the radiation characteristics during the declining phase of the 24th Solar Cycle. Since 1989 Liulin type dosemeters-spectrometers have been conducting measurements of the radiation environment characteristics onboard several manned and unmanned spacecraft in low Earth orbit or in interplanetary space ( Dachev et al. 2015). The total number of instruments built and experiments conducted is 28. ...
... The distance between the parallel Si PIN photodiodes is 20.8 mm. Further description of the instrument can be found in Semkova et al. (2015). The four detectors are in pairs one in front of the other, thus forming two perpendicular measure- ment systems. ...
Article
Full-text available
ExoMars is a two-launch mission undertaken by Roscosmos and European Space Agency. Trace Gas Orbiter, a satellite part of the 2016 launch carries the Fine Resolution Neutron Detector instrument as part of its payload. The instrument aims at mapping hydrogen content in the upper meter of Martian soil with spatial resolution between 60 and 200 km diameter spot. This resolution is achieved by a collimation module that limits the field of view of the instruments detectors. A dosimetry module that surveys the radiation environment in cruise to Mars and on orbit around it is another part of the instrument. This paper describes the mission and the instrument, its measurement principles and technical characteristics. We perform an initial assessment of our sensitivity and time required to achieve the mission goal. The Martian atmosphere is a parameter that needs to be considered in data analysis of a collimated neutron instrument. This factor is described in a section of this paper. Finally, the first data accumulated during cruise to Mars is presented.
... The average radiation dose measured on the surface of ISS for this period is 425 KGy [ 8,9 ]. The cosmic radiation increases in missions to Mars [ 10 ]. It grows particularly strong at the onset of solar cosmic rays and high energetic particles in interplanetary space [11][12][13][14][15]. ...
Article
Full-text available
In this paper we present a study on the mechanical properties of nanodiamond enhanced tungsten strengthened aluminium alloy 7075, stored for 28 months under different conditions. One of the samples was stored in terrestrial conditions and the other sample was mounted on the outside of the International Space Station for the same period. The purpose of the experiment is to determine tensile strength, Young’s modulus and Poissonâ‚™s ratio using different testing procedures and to compare the results with those obtained using the ultrasonic volumetric method.
... Liulin type instruments have been used onboard Mir Space Station, in many experiments on ISS, Foton M2/M3/M4, Chandrayaan-1, Phobos-Grunt, and BION satellites. New Liulin type instrumentation is used for radiation investigations during the ExoMars TGO mission ( Semkova et al., 2015 ). The dosimeter Liulin-MO is a module of the Fine Resolution Epithermal Neutron Detector (FREND) onboard the TGO. ...
Article
ExoMars is a joint ESA—Rosscosmos program for investigating Mars. Two missions are foreseen within this program: one consisting of the Trace Gas Orbiter (TGO), that carries scientific instruments for the detection of trace gases in the Martian atmosphere and for the location of their source regions, plus an Entry, Descent and landing demonstrator Module (EDM), launched on March 14, 2016; and the other, featuring a rover and a surface platform, with a launch date of 2020. On October 19, 2016 TGO was inserted into high elliptic Mars’ orbit. The dosimetric telescope Liulin-MO for measuring the radiation environment onboard the ExoMars 2016 TGO is a module of the Fine Resolution Epithermal Neutron Detector (FREND). Here we present first results from measurements of the charged particle fluxes, dose rates, Linear Energy Transfer (LET) spectra and estimation of dose equivalent rates in the interplanetary space during the cruise of TGO to Mars and first results from dosimetric measurements in high elliptic Mars’ orbit. A comparison is made with the dose rates obtained by RAD instrument onboard Mars Science Laboratory during the cruise to Mars in 2011–2012 and with the Galactic Cosmic Rays (GCR) count rates provided by other particle detectors currently in space. The average measured dose rate in Si from GCR during the transit to Mars for the period April 22–September 15, 2016 is 372 ± 37 µGy d⁻¹ and 390 ± 39 µGy d⁻¹ in two perpendicular directions. The dose equivalent rate from GCR for the same time period is about 2 ± 0.3 mSv d−1. This is in good agreement with RAD results for radiation dose rate in Si from GCR in the interplanetary space, taking into account the different solar activity during the measurements of both instruments. About 10% increase of the dose rate, and 15% increase of the dose equivalent rate for 10.5 months flight is observed. It is due to the increase of Liulin-MO particle fluxes for that period and corresponds to the overall GCR intensity increase during the declining phase of the solar activity. Data show that during the cruise to Mars and back (6 months in each direction), taken during the declining of solar activity, the crewmembers of future manned flights to Mars will accumulate at least 60% of the total dose limit for the cosmonaut's/astronaut's career in case their shielding conditions are close to the average shielding of Liulin-MO detectors—about 10 g cm⁻². The dosimetric measurements in high elliptic Mars’ orbit demonstrate strong dependence of the GCR fluxes near the TGO pericenter on satellite's field of view shadowed by Mars.
Chapter
ExoMars is the climax of European-Russian cooperation, a joint double mission and the second largest area of cooperation after the International Space Station (ISS). This chapter looks at the origins of the mission in an early century European rover project, the development of the two-stage project and then the first mission in 2016, which saw the Trace Gas Orbiter enter Mars orbit but the Schiaparelli lander fail. The mission took place against a background of rising political tensions between Europe and Russia over Ukraine and Crimea, with the reinstatement of the sanctions regime once again affecting their relationship.
Article
Full-text available
An account is provided of the main sources of energetic particle radiation in interplanetary space (Galactic Cosmic Radiation and Solar Energetic Particles) and career dose limits presently utilized by NASA to mitigate against the cancer and non-cancer effects potentially incurred by astronauts due to irradiation by these components are presented. Certain gaps in knowledge that presently militate against mounting viable human exploration in deep space due to the inherent health risks are identified and recommendations made as to how these gaps might be closed within a framework of global international cooperation.
Article
Full-text available
Ionizing radiation is recognized to be one of the main health concerns for humans in the space radiation environment. Estimation of space radiation effects on health requires the accurate knowledge of the accumulated absorbed dose, which depends on the global space radiation distribution, solar cycle and local shielding generated by the 3D mass distribution of the space vehicle. This paper presents an overview of the spectrometer-dosimeters of the Liulin type, which were developed in the late 1980s and have been in use since then. Two major measurement systems have been developed by our team. The first one is based on one silicon detector and is known as a Liulin-type deposited energy spectrometer (DES) (Dachev et al., 2002, 2003), while the second one is a dosimetric telescope (DT) with two or three silicon detectors. The Liulin-type instruments were calibrated using a number of radioactive sources and particle accelerators. The main results of the calibrations are presented in the paper. In the last section of the paper some of the most significant scientific results obtained in space and on aircraft, balloon and rocket flights since 1989 are presented. Copyright © 2015 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.
Article
Full-text available
This paper describes the Liulin-Phobos experiment, which will be flown onboard the future Phobos - Soil sample return mission to the satellite of Mars - Phobos. The main goal is the investigation of the radiation environment and doses on the path and on Phobos surface.
Article
Full-text available
The RADiatiOn Monitor (RADOM) is a miniature dosimeter-spectrometer that flew onboard the Chandrayaan-1 lunar mission in order to monitor the local radiation environment. Primary objective of the RADOM experiment was to measure the total absorbed dose, flux of surrounding energetic particles and spectrum of the deposited energy from high energy particles both en-route and in lunar orbit. RADOM was the first experiment to be switched on after the launch of Chandrayaan-1 and was operational until the end of the mission. This paper summarizes the observations carried out by RADOM during the entire life time (22 October 2008–31 August 2009) of the Chandrayaan-1 mission and compares the measurement by RADOM with the radiation belt models such as AP-8, AE-8 and CRRESS.
Article
The ability to evaluate the cosmic ray environment at Mars is of interest for future manned exploration. To support exploration, tools must be developed to accurately access the radiation environment in both free space and on planetary surfaces. The primary tool NASA uses to quantify radiation exposure behind shielding materials is the space radiation transport code, HZETRN. In order to build confidence in HZETRN, code benchmarking against Monte Carlo radiation transport codes is often used. This work compares the dose calculations at Mars by HZETRN and the Geant4 application Planetocosmics. The dose at ground and the energy deposited in the atmosphere by galactic cosmic ray protons and alpha particles has been calculated for the Curiosity landing conditions. In addition, this work has considered Solar Energetic Particle events, allowing for the comparison of varying input radiation environments. The results for protons and alpha particles show very good agreement between HZETRN and Planetocosmics.
Article
In the last few years an essential progress in development of physical models for cosmic ray induced ionization in the atmosphere is achieved. The majority of these models are full target, i.e. based on Monte Carlo simulation of an electromagnetic-muon-nucleon cascade in the atmosphere. Basically, the contribution of proton nuclei is highlighted, i.e. the contribution of primary cosmic ray alpha-particles and heavy nuclei to the atmospheric ionization is neglected or scaled to protons. The development of cosmic ray induced atmospheric cascade is sensitive to the energy and mass of the primary cosmic ray particle. The largest uncertainties in Monte Carlo simulations of a cascade in the Earth atmosphere are due to assumed hadron interaction models, the so-called hadron generators. In the work presented here we compare the ionization yield functions Y for primary cosmic ray nuclei, such as alpha-particles, Oxygen and Iron nuclei, assuming different hadron interaction models. The computations are fulfilled with the CORSIKA 6.9 code using GHEISHA 2002, FLUKA 2011, UrQMD hadron generators for energy below 80 GeV/nucleon and QGSJET II for energy above 80 GeV/nucleon. The observed difference between hadron generators is widely discussed. The influence of different atmospheric parametrizations, namely US standard atmosphere, US standard atmosphere winter and summer profiles on ion production rate is studied. Assuming realistic primary cosmic ray mass composition, the ion production rate is obtained at several rigidity cut-offs - from 1 GV (high latitudes) to 15 GV (equatorial latitudes) using various hadron generators. The computations are compared with experimental data. A conclusion concerning the consistency of the hadron generators is stated.
Article
The Radiation Assessment Detector (RAD) on the Mars Science Laboratory’s Curiosity rover began making detailed measurements of the cosmic ray and energetic particle radiation environment on the surface of Mars on 7 August 2012. We report and discuss measurements of the absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the martian surface for ~300 days of observations during the current solar maximum. These measurements provide insight into the radiation hazards associated with a human mission to the surface of Mars and provide an anchor point with which to model the subsurface radiation environment, with implications for microbial survival times of any possible extant or past life, as well as for the preservation of potential organic biosignatures of the ancient martian environment.
Article
Results for the radiation environment to be found on the planet Mars due to Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE) has been obtained. Primary particle environments computed for Martian conditions are transported within the Mars atmosphere, modeled in a time-dependent way in terms of density, pressure, and temperature vs. altitude, down to the surface, with topography and backscattering patterns taken into account. The atmospheric chemical and isotopic composition has been modeled over results from the in-situ Viking Lander measurements for both major and minor components. The surface topography has been determined by using a model based on the data provided by the Mars Orbiter Laser Altimeter (MOLA) instrument on board the Mars Global Surveyor (MGS) spacecraft. The surface itself has been modeled in both the dry (‘regolith’) and volatile components. Mars regolith composition has been modeled based on the measurements obtained with orbiter and lander spacecraft from which an average composition has been derived. The volatile inventory properties, both in the regolith and in the seasonal and perennial polar caps, has been taken into account by modeling the deposition of volatiles and its variations with geography and time all throughout the Martian year, from results from imaging data of orbiter spacecraft. Results are given in terms of fluxes, doses and LET, for most kinds of particles, namely protons, neutrons, alpha particles, heavy ions, pions, and muons for various soil compositions.
Article
This paper presents a new model for the ionization of cosmic rays in the atmosphere of Mars, based on an engineering model for the Martian atmosphere developed by Moroz et al. (1988). Based on the theoretical model, a computer program was developed in TURBO-PASCAL. The q(h) profiles (where q is the rate of electron production at a height h) at the minimum and the maximum of solar activity calculated for summer in the northern Martian atmosphere, and for winter in the southern hemisphere are presented.