Neutron dosimetry in low-earth orbit using passive detectors

Area of Science:

• Space physics
• Radiation detection
• Dosimetry

Background:

• Spacecraft missions involve significant radiation exposure.
• Accurate neutron dosimetry is crucial for astronaut safety and mission planning.

Purpose of the Study:

• To summarize 20 years of neutron dosimetry measurements on US and Russian LEO spacecraft.
• To reanalyze neutron data in terms of ambient dose equivalent.
• To compare measured neutron dose contributions with model estimates.

Main Methods:

• Utilized passive detectors: thermal/resonance neutron detectors (for <1 MeV neutrons) and fission foil detectors (for >1 MeV neutrons).
• Measurements were conducted aboard US and Russian Low Earth Orbit (LEO) spacecraft over two decades.
• Data were reanalyzed using ambient dose equivalent, updating from NCRP-38 quality factor definitions.

Main Results:

• Dose equivalent rates for neutrons <1 MeV varied from 0.80 to 22.0 microSv/d.
• Dose equivalent rates for neutrons >1 MeV ranged from 4.5 to 172 microSv/d (on LDEF mission).
• Neutrons >1 MeV accounted for over 98% of the total neutron dose equivalent on the LDEF mission.

Conclusions:

• Neutrons, particularly those with energies >1 MeV, are the primary contributors to neutron dose equivalent in space.
• Measured neutron dose contributions were generally lower than model estimates.
• Passive dosimetry provides valuable data for understanding space radiation environments.