Radiation exposure measurement onboard civil aircraft.

The active dosemeter DOSTEL based on two silicon planar detectors was flown on civil aircraft flights to study the radiation exposure of air crew members. The altitude and latitude dependence of count and dose rates as well as long-term variations are measured. After calibration of the DOSTEL response against measurements of a TEPC instrument, total dose-equivalent values for various flights are compared with H*(10) calculations by EPCARD yielding a ratio of 1.02 +/- 0.09 (standard variation).

Space radiation measurements on-board ISS--the DOSMAP experiment.

The experiment 'Dosimetric Mapping' conducted as part of the science program of NASA's Human Research Facility (HRF) between March and August 2001 was designed to measure integrated total absorbed doses (ionising radiation and neutrons), heavy ion fluxes and its energy, mass and linear energy transfer (LET) spectra, time-dependent count rates of charged particles and their corresponding dose rates at different locations inside the US Lab at the International Space Station. Owing to the variety of particles and energies, a dosimetry package consisting of thermoluminescence dosemeter (TLD) chips and nuclear track detectors with and without converters (NTDPs), a silicon dosimetry telescope (DOSTEL), four mobile silicon detector units (MDUs) and a TLD reader unit (PILLE) with 12 TLD bulbs as dosemeters was used. Dose rates of the ionising part of the radiation field measured with TLD bulbs applying the PILLE readout system at different locations varied between 153 and 231 microGy d(-1). The dose rate received by the active devices fits excellent to the TLD measurements and is significantly lower compared with measurements for the Shuttle (STS) to MIR missions. The comparison of the absorbed doses from passive and active devices showed an agreement within +/- 10%. The DOSTEL measurements in the HRF location yielded a mean dose equivalent rate of 535 microSv d(-1). DOSTEL measurements were also obtained during the Solar Particle Event on 15 April 2001.

Personal dosimetry for human missions to Mars based on TLD and LET-spectrometry technique.

Exposure of crew to the space radiation environment poses one of the most significant problems in long term missions in low earth orbits and in interplanetary missions. Accurate personal dose measurement will become increasingly important especially during manned missions to Mars. A series of instruments suitable for on-board dose, flux and LET measurements has been developed by the authors'. Based on the experience gained so far from their utilization, an instrument consisting of a thermoluminescent device and a dosimetry telescope is proposed for the use on the International Space Station and for human Mars missions. The short technical description of this instrument is given in this paper.

Radiation measurements on the Mir Orbital Station.

Radiation measurements made onboard the MIR Orbital Station have spanned nearly a decade and covered two solar cycles, including one of the largest solar particle events, one of the largest magnetic storms, and a mean solar radio flux level reaching 250 x 10(4) Jansky that has been observed in the last 40 years. The cosmonaut absorbed dose rates varied from about 450 microGy day-1 during solar minimum to approximately half this value during the last solar maximum. There is a factor of about two in dose rate within a given module, and a similar variation from module to module. The average radiation quality factor during solar minimum, using the ICRP-26 definition, was about 2.4. The drift of the South Atlantic Anomaly was measured to be 6.0 +/- 0.5 degrees W, and 1.6 +/- 0.5 degrees N. These measurements are of direct applicability to the International Space Station. This paper represents a comprehensive review of Mir Space Station radiation data available from a variety of sources.

Dosimetry inside MIR station using a silicon detector telescope (DOSTEL).

The dosimetry telescope (DOSTEL) was flown on the MIR orbital station during October 1997-January 1998. The mission average contributions to the absorbed dose rates (in water) were 126 +/- 4 microGy/d and 121 +/- 13 microGy/d for the GCR and the SAA component, respectively. The mean quality factors (ICRP60) deduced from the LET-spectra are 3.5 +/- 0.2 (GCR) and 1.3 +/- 0.1 (SAA). Separate LET spectra and temporal variations of the absorbed dose rates and of the mean quality factors are presented for these two radiation components as well as for solar energetic particles of the November 6, 1997 event.

Calibration results obtained with Liulin-4 type dosimeters.

The Mobile Radiation Exposure Control System's (Liulin-4 type) main purpose is to monitor simultaneously the doses and fluxes at 4 independent places. It can also be used for personnel dosimetry. The system consists of 4 battery-operated 256-channel dosimeters-spectrometers. We describe results obtained during the calibrations of the spectrometers at the Cyclotron facilities of the University of Louvain, Belgium and of the National Institute of Radiological Sciences-STA, Chiba, Japan with protons of energies up to 70 MeV. The angular sensitivities of the devices are studied and compared with Monte-Carlo predictions. We also present the results obtained at the HIMAC accelerator with 500 MeV/u Fe ions and at the CERN high energy radiation reference fields. Records made during airplane flights are shown and compared with the predictions of the CARI-6 model.

Estimation of neutron and other radiation exposure components in low earth orbit.

The interaction of high-energy space radiation with spacecraft materials generates a host of secondary particles, some, such as neutrons, are more biologically damaging and penetrating than the original primary particles. Before committing astronauts to long term exposure in such high radiation environments, a quantitative understanding of the exposure and estimates of the associated risks are required. Energetic neutrons are traditionally difficult to measure due to their neutral charge. Measurement methods have been limited by mass and weight requirements in space to nuclear emulsion, activation foils, a limited number of Bonner spheres, and TEPCs. Such measurements have had limited success in quantifying the neutron component relative to the charged components. We will show that a combination of computational models and experimental measurements can be used as a quantitative tool to evaluate the radiation environment within the Shuttle, including neutrons. Comparisons with space measurements are made with special emphasis on neutron sensitive and insensitive devices.

HZE dosimetry in space using plastic track detectors.

Plastic nuclear track detectors were used to measure the contribution of High charge Z and energy E (HZE) particles to the radiation exposure of manned space missions. Results from numerous space missions in the orbit planned for the International Space Station are compared. The measurements cover the declining phase of the last solar cycle during the past 7 years and various shielding conditions inside the US Space Shuttle and the Russian MIR-station.

Energy spectra of geomagnetically trapped oxygen ions.

In a series of COSMOS satellite flights plastic nuclear track detectors have been exposed in low-earth orbits to monitor anomalous cosmic rays (ACR) at energies below 25 MeV/nuc. The analysis of energy spectra has now been extended to energies up to 40 MeV/nuc for two exposures aboard COSMOS 2260 in 1993 and COSMOS 2311 in 1995. Our data on trapped ACR (TACR) oxygen energy spectra might indicate the influence of energy-dependent stripping probabilities and the presence of multiply charged ACR oxygen at high energies as reported by latest SAMPEX observations.

Recent European measurements inside Biorack.

The dosimetric package used inside Biorack on board STS76, STS81 and STS84 comprises passive detector stacks built from plastic nuclear track detectors (PNTDs), thermoluminescence detectors (TLDs) and one or two active DOSTEL (DOSimetric TELescope) units using planar silicon detectors. Five passive detector stacks were exposed at different places inside the BIORACK incubators and in different stowage positions. DOSTEL units were exposed inside the 22 degrees C incubator in all flights. Mission integrated dose measurements, particle fluence rates and neutron doses are obtained from the passive detector stacks. These results are complemented by time resolved particle counts and dose rates and linear energy transfer (LET) spectra separately for the contribution of the trapped particles and the galactic cosmic rays (GCR) as a result of the DOSTEL measurements. In addition, it was possible to investigate the anisotropy of the radiation field inside Biorack by the use of a second DOSTEL unit on STS84. Since all exposures are during a solar minimum period, the total radiation exposure is of a similar extent for all flights, although position differences in dose rate up to a factor of two are observed. Particle fluence rates show lower variations. Mission averaged mean quality factors (Q) determined from the LET spectra are 2.0+/-0.1; the deduced dose equivalent rates range from 631 to 716 microSv/day.

Active dosimetry on recent space flights.

The radiation exposure inside the spacecraft in low earth orbit was investigated with a telescope based on two silicon planar detectors during three NASA shuttle-to-MIR missions (inclination 51.6 deg, altitude about 380 km). Count and dose rate profiles were measured, as well as separate linear energy transfer (LET) spectra, for the galactic cosmic rays (GCR) and the trapped radiation encountered in the South Atlantic Anomaly (SAA). Effective quality factors are deduced from the converted LET spectra (in water) in the range 0.1-120 keV micrometer-1 according to ICRP 60. Measured mission averaged dose rates in silicon are in the range 98-108 microGy d-1 and 137-178 microGy d-1 for the GCR and SAA contributions, respectively. The deduced effective quality factors are 2.95-3.29 (GCR) and 1.18-1.25 (SAA), resulting in mission averaged dose equivalent rates of 631-716 microSv d-1 for the comparable three missions.

Measurements of radiation exposure in civil aircraft.

The radiation exposures on 12 flights of German airlines were measured with an active dosemeter based on two silicon semiconductors. The dependence on the date, altitude and route of the flights was studied. Measured dose rates and preliminary dose equivalent rates of the individual flights are given and compared with model calculations.

Results of dosimetric measurements in space missions.

Detector packages consisting of plastic nuclear track detectors, nuclear emulsions, and theromoluminescence detectors were exposed at different locations inside the space laboratory Spacelab and at the astronauts' body and in different sections of the MIR space station. Total dose, particle fluence rate and linear energy transfer (LET) spectra of heavy ions, number of nuclear disintegrations and fast neutron fluence rates were determined of each exposure. The dose equivalent received by the Payload specialists (PSs) were calculated from the measurements, they range from 190 microSv d-1 to 770 microSv d-1. Finally, a preliminary investigation of results from a particle telescope of two silicon detectors, first used in the last BIORACK mission on STS 76, is reported.

Results of dosimetric measurements in space missions.

Detector packages consisting of thermoluminescence detectors (TLDs), nuclear emulsions and plastic nuclear track detectors were exposed in different locations inside spacecraft. The detector systems, which supplement each other in their registration characteristics, allow the recording of biologically relevant portions of the radiation field independently. Results are presented and compared with calculations. Dose equivalents for the astronauts have been calculated based on the measurements; they lie between 190 microSv d-1 and 860 microSv d-1.

Heavy ion results from different locations on LDEF.

Heavy ions (Z = 8-26) with energies far below the geomagnetic cutoff energy were measured in three different plastic nuclear track detector experiments on the 28.5 degrees inclination orbit of the NASA satellite Long Duration Exposure Facility (LDEF) at 460 km mean altitude. The results of the three experiments M0002 (Kiel University, Germany), A0015 (Deutsche Gesellschaft fur Luft- und Raumfahrt (= DLR) Koln, Germany) and HIIS (Naval Research Laboratory (= NRL) Washington, DC, U.S.A.), which were exposed at different satellite locations, agree with each other. At E < or = 70 MeV/nuc all particle groups showed a steeply falling energy spectrum and an anisotropic arrival direction distribution. The results were consistent with magnetically trapped particles registered in the South Atlantic. The detected particles originated from the anomalous cosmic rays (O, Ne, Ar) and from an unknown source (Mg, Si, Fe). At E > or = 70 MeV/nuc measured particles of the Fe-group showed a flattening energy spectrum.

Dosimetry on the Spacelab missions IML1 and IML2, and D2 and on MIR.

Detector packages consisting of plastic nuclear track detectors, nuclear emulsions, and thermoluminescence detectors were exposed inside BIORACK during the Spacelab missions IML1 and IML2, in different sections of the MIR space station, and inside the Spacelab module at rack front panels or stowage lockers and in the Spacelab tunnel during D2. In addition, during D2, each Payload Specialist (PS) has worn three permanent detector packages; one at the neck; one at the waist; and one at the ankle. Total dose measurements, particle fluence rate and LET spectra, number of nuclear disintegrations and neutron dose from this exposure are given in this report. The results are compared to theoretical calculations and to previous missions results. The dose equivalent (total radiation exposure) received by the PSs were calculated from the measurements and range from 190 to 770 microSv d-1. Finally, a cursory investigation of results from a particle telescope from two silicon detectors, first used in the last BIORACK mission on STS76, is reported.

Dosimetric mapping in BIORACK on IML2.

Seven detector packages consisting of plastic nuclear track detectors, nuclear emulsions and thermoluminescence dosimeters were exposed in different locations inside BIORACK during the IML2 mission. The detectors supplement each other in their registration characteristics and cover well the different contributions of the space radiations to the dose. In this report, results are given on total dose measurements, cosmic ray flux and neutron dose. Total doses differ by up to a factor of 1.5 and heavy ion fluxes by more than a factor of 6 in the different locations. The results are compared with those of previous missions. The mission equivalent dose for the astronauts was calculated from the measurements to be 3.8 mSv.

On the origin of trapped heavy ions at L = 1.4-1.6.

Aboard the NASA satellite Long Duration Exposure Facility (LDEF) heavy ions of nuclear charge Z = 8-26 were detected with energies between 15 and 50 MeV/nuc which are far below the cutoff energy required of fully stripped ions to reach the LDEF orbit. The arrival directions and the falling energy spectra of these particles are consistent with a trapped component incident in the South Atlantic Anomaly at L = 1.4-1.6. The trapped oxygen, neon and argon ions probably originate from the anomalous cosmic rays, whereas the origin of the other particles like magnesium, silicon and iron is not yet solved but may be associated with the October 89 solar energetic particle events.

Dosimetric measurements in manned missions.

Detector packages consisting of thermoluminescence detectors (TLDs), nuclear emulsions and plastic nuclear track detectors were exposed in different sections of the MIR space station, inside the Spacelab during the IML1 mission, and inside Spacelab module and tunnel during the D2 mission. This report concentrates on total dose measurements with TLDs during these mission. The results are discussed and compared to results of former missions and to calculations. Finally, dose equivalents and mean quality factors for each mission are presented which are derived from the TLD results and results obtained from the other detector systems. Dose equivalents range between 200 microSvd-1 and 700 microSvd-1.

Dosimetric results on EURECA.

Detector packages were exposed on the European Retrievable Carrier (EURECA) as part of the Biostack experiment inside the Exobiology and Radiation Assembly (ERA) and at several locations around EURECA. The packages consist of different plastic nuclear track detectors, nuclear emulsions and thermoluminescence dosimeters (TLDs). Evaluation of these detectors yields data on absorbed dose and particle and linear energy transfer (LET) spectra. Behind a shielding thickness in front of the detectors of 0.09g cm-2 the doses range between 21.26 Gy and 0.87 Gy depending on the location of the dosimeter. Not all measurement can be explained by calculations.