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High dose rates obtained outside ISS in June 2015 during SEP event
T P Dachev1, B T Tomov1, Yu N Matviichuk1
1Space Research and Technology Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Block 1, 1113 Sofia, Bulgaria.
Life Sciences in Space Research
|June 28, 2016
Summary
Solar energetic particle (SEP) events pose significant radiation risks to astronauts. A large SEP event on June 22, 2015, generated high dose rates outside the International Space Station (ISS), comparable to internal ISS doses over 15 days.
Area of Science:
- Space physics and radiation dosimetry.
- Investigating space radiation environments and their biological impacts.
Background:
- The R3DR2 instrument, a Liulin-type deposited energy spectrometer (DES), operated on the European Space Agency's EXPOSE-R2 platform outside the ISS from October 2014 to January 2016.
- Previous studies have monitored smaller solar energetic particle (SEP) events using similar instruments outside the ISS.
Purpose of the Study:
- To characterize the dosimetric properties of the largest SEP event recorded by the R3DR2 instrument outside the ISS on June 22, 2015.
- To assess the potential radiation dose to astronauts during extravehicular activities (EVAs) during such extreme SEP events.
Main Methods:
- Utilized the R3DR2 deposited energy spectrometer to measure radiation doses outside the ISS.
- Analyzed data from a significant SEP event on June 22, 2015.
- Compared measured SEP doses with radiation belt doses and estimated astronaut skin doses during simulated EVAs.
Main Results:
- SEP protons with a minimum energy of approximately 7 MeV generated high dose rates exceeding 5000 µGy/h outside the ISS.
- This SEP event's dose rate was significantly higher than the maximum dose rate from the inner radiation belt (2200 µGy/h).
- A 6.5-hour simulated EVA during the SEP peak could result in astronaut skin doses of 2.84 mGy, similar to 15 days of internal ISS exposure.
Conclusions:
- SEP events, like the one on June 22, 2015, represent a major radiation hazard for astronauts, particularly during EVAs.
- Liulin-type instruments provide crucial data for understanding and mitigating risks from extreme space radiation events.
- Findings highlight the need for enhanced radiation protection strategies for astronauts undertaking EVAs in space.
