Expose – R Radiation Risks Raiometer-Dosimeter (Expose-R R3DR)
Research Area: Astrobiology
Expedition(s): 18- 26
Principal Investigator(s): ● Tsvetan Dachev, Institute, Bulgarian Academy of Sciences,
Sofia, Bulgaria
RESEARCH OBJECTIVES
The Expose-R facility hosts a suite of
astrobiology experiments, some of which
could help understand how life originated
on Earth. This suite of experiments are
accommodated in 3 special sample trays,
which are loaded with a variety of
biological samples and exposed to the
harsh environment of open space for
almost 2 years from March 2009-January- This investigation records with time
resolution, the dose of solar light over 4
wavelength ranges as well as the flux of
heavy cosmic particles. Relativistic
Electron Precipitations (REP) have been
observed for many years. Electrons with energies of a few MeV can penetrate the spacecraft
shielding and can cause damage to sensitive electronic preamplifiers and whole systems of the
spacecraft. The total dose of an astronaut on a 6-hour spacewalk inside the REP, has also been
estimated to exceed the astronaut’s short-term limits for both skin and eyes. The main idea of
the analysis of daily fluences on the International Space Station (ISS) is to underline that REP
events are common on ISS.
RESULTS
Comparison between the relativistic electron dose rate data measured by the R3D instrument
on ESA’s EuTEF facility (R3DE) and R3DR showed that during periods of simultaneous operation
the R3DR dose rates were higher than for R3DE because the R3DR instrument was in a less
shielded surrounding. The conclusion was that astronauts on EVA collect highly variable dose
rates during REP in dependence of their position around the station. Only active personal
dosimeters were able to accurately measure these large variations.
The most interesting period was between April and August 2010. The R3DR and GOES-11 daily
relativistic electron fluences greatly increased on of April 6 and 7. Solar activity was at very low
levels with isolated low-level B-class flares, and a halo coronal mass ejection was observed on
April 3. The main conclusion of the research was that REP events were common on the ISS and
require additional comprehensive investigations (Dachev 2012).
ISS018E039266 – View of Expose-R as it is being set up
with Earth in the background.