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1.
Adv Space Res ; 31(4): 841-6, 2003.
Article in English | MEDLINE | ID: mdl-14503488

ABSTRACT

We have a developed a dynamic cutoff rigidity model based on computed world grids of vertical cutoff rigidities derived from employing the Tsyganenko magnetospheric model. The dynamic range of this model covers all magnetic activity levels specified by integer values of the Kp magnetic index. We present comparisons of the measured dose observed on the space shuttle during the August 1989 solar proton event with the dose computed from solar particles predicted to be allowed through the magnetosphere to the space shuttle position. We find a one-to-one correspondence between the portion of the orbit predicted to be subjected to solar protons and the portion of the orbit where solar particle dose measurements were obtained.


Subject(s)
Cosmic Radiation , Magnetics , Models, Statistical , Radiation Monitoring/statistics & numerical data , Solar Activity , Space Flight , Extraterrestrial Environment , Occupational Exposure/statistics & numerical data , Protons , Radiation Dosage , Spacecraft , Weightlessness
2.
Radiat Meas ; 26(2): 147-58, 1996 Mar.
Article in English | MEDLINE | ID: mdl-11539200

ABSTRACT

A tissue equivalent proportional counter designed to measure the linear energy transfer spectra (LET) in the range 0.2-1250 keV/micrometer was flown in the Kvant module on the Mir orbital station during September 1994. The spacecraft was in a 51.65 degrees inclination, elliptical (390 x 402 km) orbit. This is nearly the lower limit of its flight altitude. The total absorbed dose rate measured was 411.3 +/- 4.41 microGy/day with an average quality factor of 2.44. The galactic cosmic radiation (GCR) dose rate was 133.6 microGy/day with a quality factor of 3.35. The trapped radiation belt dose rate was 277.7 microGy/day with an average quality factor of 1.94. The peak rate through the South Atlantic Anomaly was approximately 12 microGy/min and nearly constant from one pass to another. A detailed comparison of the measured LET spectra has been made with radiation transport models. The GCR results are in good agreement with model calculations; however, this is not the case for radiation belt particles and again points to the need for improving the AP8 omni-directional trapped proton models.


Subject(s)
Cosmic Radiation , Linear Energy Transfer , Models, Theoretical , Protons , Solar Activity , Space Flight/instrumentation , Brazil , Neutrons , Radiation Dosage , Radiation Monitoring/instrumentation , Radiometry/instrumentation
3.
Radiat Meas ; 26(1): 17-34, 1996 Jan.
Article in English | MEDLINE | ID: mdl-11539199

ABSTRACT

A joint investigation between the United States and Russia to study the radiation environment inside the Space Shuttle flight STS-60 was carried out as part of the Shuttle-Mir Science Program (Phase 1). This is the first direct comparison of a number of different dosimetric measurement techniques between the two countries. STS-60 was launched on 3 February 1994 in a nearly circular 57 degrees x 353 km orbit with five U.S. astronauts and one Russian cosmonaut for 8.3 days. A variety of instruments provided crew radiation exposure, absorbed doses at fixed locations, neutron fluence and dose equivalent, linear energy transfer (LET) spectra of trapped and galactic cosmic radiation, and energy spectra and angular distribution of trapped protons. In general, there is good agreement between the U.S. and Russian measurements. The AP8 Min trapped proton model predicts an average of 1.8 times the measured absorbed dose. The average quality factor determined from measured lineal energy, y, spectra using a tissue equivalent proportional counter (TEPC), is in good agreement with that derived from the high temperature peak in the 6LiF thermoluminescent detectors (TLDs). The radiation exposure in the mid-deck locker from neutrons below 1 MeV was 2.53 +/- 1.33 microSv/day. The absorbed dose rates measured using a tissue equivalent proportional counter, were 171.1 +/- 0.4 and 127.4 +/- 0.4 microGy/day for trapped particles and galactic cosmic rays, respectively. The combined dose rate of 298.5 +/- 0.82 microGy/day is about a factor of 1.4 higher than that measured using TLDs. The westward longitude drift of the South Atlantic Anomaly (SAA) is estimated to be 0.22 +/- 0.02 degrees/y. We evaluated the effects of spacecraft attitudes on TEPC dose rates due to the highly anisotropic low-earth orbit proton environment. Changes in spacecraft attitude resulted in dose-rate variations by factors of up to 2 at the location of the TEPC.


Subject(s)
Neutrons , Protons , Radiation Monitoring/instrumentation , Space Flight/instrumentation , Thermoluminescent Dosimetry/instrumentation , Atlantic Ocean , Humans , International Cooperation , Linear Energy Transfer , Radiation Dosage , Radiometry , Russia , Solar Activity , United States
4.
Adv Space Res ; 14(10): 923-6, 1994 Oct.
Article in English | MEDLINE | ID: mdl-11540036

ABSTRACT

Time-resolved radiation exposure measurements inside the crew compartment have been made during recent Shuttle missions with the USAF Radiation Monitoring Equipment-III (RME-III), a portable four-channel tissue equivalent proportional counter. Results from the first six missions are presented and discussed. The missions had orbital inclinations ranging from 28.5 degrees to 57 degrees, and altitudes from 200-600 km. Dose equivalent rates ranged from 40-5300 micro Sv/dy. The RME-III measurements are in good agreement with other dosimetry measurements made aboard the vehicle. Measurements indicate that medium- and high-LET particles contribute less than 2% of the particle fluence for all missions, but up to 50% of the dose equivalent, depending on the spacecraft's altitude and orbital inclination. Iso-dose rate contours have been developed from measurements made during the STS-28 mission. The drift rate of the South Atlantic Anomaly (SAA) is estimated to be 0.49 degrees W/yr and 0.12 degrees N/yr. The calculated trapped proton and Galactic Cosmic Radiation (GCR) dose for the STS-28 mission were significantly lower than the measured values.


Subject(s)
Cosmic Radiation , Protons , Radiation Monitoring/instrumentation , Solar Activity , Space Flight/instrumentation , Spacecraft/instrumentation , Linear Energy Transfer , Radiation Dosage , Radiometry/instrumentation
5.
Radiat Meas ; 23(1): 25-42, 1994 Jan.
Article in English | MEDLINE | ID: mdl-11538011

ABSTRACT

Time-resolved radiation dosimetry measurements inside the crew compartment have been made during recent Shuttle missions with the U.S. Air Force Radiation Monitoring Equipment-III (RME-III), a portable battery-powered four-channel tissue equivalent proportional counter. Results from the first six missions are presented and discussed. Half of the missions had orbital inclinations of 28.5 degrees with the remainder at inclinations of 57 degrees or greater; altitudes ranged from 300 to 600 km. The determined dose equivalent rates ranged from 70 to 5300 microSv/day. The RME-III measurements are in good agreement with other dosimetry measurements made aboard the vehicles. Measurements indicate that medium- and high-LET particles contribute less than 2% of the particle fluence for all missions, but up to 50% of the dose equivalent, depending on the spacecraft's altitude and orbital inclination. Isocontours of fluence, dose and dose equivalent rate have been developed from measurements made during the STS-28 mission. The drift rate of the South Atlantic Anomaly is estimated to be 0.49 degrees W/yr and 0.12 degrees N/yr. The calculated trapped proton and GCR dose for the STS-28 mission was significantly lower than the measured values.


Subject(s)
Cosmic Radiation , Extraterrestrial Environment , Protons , Radiation Monitoring/instrumentation , Solar Activity , Space Flight/instrumentation , Atlantic Ocean , Equipment Design , Linear Energy Transfer , Radiation Dosage , Radiometry/instrumentation , South America , Spacecraft/instrumentation
6.
Adv Space Res ; 14(10): 661-70, 1994.
Article in English | MEDLINE | ID: mdl-11538031

ABSTRACT

The solar particle events (SPE) will contain a primary alpha particle component, representing a possible increase in the potential risk to astronauts during an SPE over the often studied proton component. We discuss the physical interactions of alpha particles important in describing the transport of these particles through spacecraft and body shielding. Models of light ion reactions are presented and their effects on energy and linear energy transfer (LET) spectra in shielding discussed. We present predictions of particle spectra, dose, and dose equivalent in organs of interest for SPE spectra typical of those occurring in recent solar cycles. The large events of solar cycle 19 are found to have substantial increase in biological risk from alpha particles, including a large increase in secondary neutron production from alpha particle breakup.


Subject(s)
Alpha Particles/adverse effects , Computer Simulation , Models, Theoretical , Radiation Protection/statistics & numerical data , Solar System , Aluminum , Cosmic Radiation , Dose-Response Relationship, Radiation , Helium , Humans , Linear Energy Transfer , Neutrons , Protons , Radiation Protection/instrumentation , Radiation Protection/methods , Risk Assessment , Space Flight , Spacecraft/instrumentation
7.
Adv Space Res ; 12(2-3): 335-8, 1992.
Article in English | MEDLINE | ID: mdl-11537026

ABSTRACT

Since STS-26, three large solar events have occurred during Shuttle missions; a geomagnetic storm during STS-29 and solar particle events (SPEs) during STS-28 and -34. The maximum dose to a crew attributed to an SPE was estimated to be 30 microGy (70 microSv). Time-resolved dosimetry measurements of the SPE dose during STS-28 were made using the Air Force Radiation Monitoring Equipment (RME)-III. Comparison of calculated and measured dose demonstrated a discrepancy, possibly a result of deficiencies in the geomagnetic cutoff model used. This experience demonstrates that dose from an SPE is strongly dependent on numerous factors such as orbit inclination, SPE start time, spectral parameters and geomagnetic field conditions; the exact combination of these factors is fortuitous. New sources of data and procedures are being investigated, including real-time tracking of auroral oval positions or determination of particle cutoff latitudes, for incorporation into operational Shuttle radiation support practices.


Subject(s)
Cosmic Radiation , Radiation Monitoring/statistics & numerical data , Solar Activity , Space Flight , Humans , Protons , Radiation Dosage , Radiation Monitoring/instrumentation , Radiometry
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