The absorbed dose to biological payloads on the International Space Station (ISS) depends on a number of factors, including date and duration of exposure and location of the payload on the ISS.
Some of the specific factors that lead to variations in the absorbed dose rate in orbit are:
- altitude (205-270 mi (330-435 km))
- when in the 11 year solar cycle the sample was exposed
- local shielding distribution around the biological sample, which in turn depends on the module in which the sample resides and the location within that module
Of these factors, the local shielding distribution is the most important.
In addition, the measured absorbed dose can vary based on the dosimetry instrument(s) used. Radiation monitoring on the ISS is not standardized across modules; each international partner has its own suite of instruments, with differing technologies, sensitivities and analysis methodologies, including criteria for distinguishing between lightly ionizing particles (mainly protons) and highly ionizing particles (mainly galactic cosmic ray nuclei).
Accuracy and precision of the measurements also varies among instruments, and this is reflected in the precision and, where available, errors in the tabulated data. For details of how the quoted doses were obtained, consult the cited literature for each payload and dosimeter.
The dose in the metadata is the dose recorded by the radiation detector closest to the sample. In most cases that detector will be in the same ISS module; in cases where data from a detector in the same module are not available, the dose is extrapolated using data from periods where data are available from detectors in multiple modules, including the module containing the payload.
ISS Modules
COL – “Columbus”, European Space Agency (ESA)
JPM – Japanese Pressurized Module, Japanese Aerospace Exploration Agency (JAXA); one of three segments in the Japanese Experiment Module “Kibo”
LAB – US Lab “Destiny”, NASA
NOD1, NOD2, NOD3 – nodes connecting ISS modules
Node 1 ("Unity") connects the U.S. and Russian segments
Node 2 ("Harmony") connects the U.S., ESA, and Japanese segments
Node 3 ("Tranquility") is attached to the port side of Node 1
SMP – Russian Service Module "Zvezda", Roscosmos
Dosimeters
Active (powered; data read out and stored and/or telemetered to ground)
DOSTEL (DOSimetry TELescope) – solid state detector
(Berger et al., https://doi.org/10.1051/swsc/2017005)
RAD (Radiation Assessment Detector) – solid state and plastic scintillator
(R. Rios, https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150016969.pdf)
REM (Radiation Environment Monitor) – solid state detector
(Stoffle et al., https://doi.org/10.1016/j.nima.2015.02.016)
R-16 Radiometer – ionization chamber
(https://www.sciencedirect.com/science/article/pii/S1350448702000847)
TEPC (Tissue Equivalent Proportion Counter)
(https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html? - id=620)
Passive (unpowered; record constantly; read out upon return to ground)
OSLD – optically stimulated luminescence detector
(Goossens et al., https://doi.org/10.1093/rpd/nci652,
Vanhavere et al., https://doi.org/10.1016/j.radmeas.2007.12.002)
PADLES (PAssive Dosimeters for Lifescience Experiments in Space) – thermoluminescence detectors, track etch detectors
(Nagamatsu et al. https://doi.org/10.1016/j.radmeas.2013.05.008)
TLD – thermoluminescence detector
(Goossens et al., https://doi.org/10.1093/rpd/nci652,
Vanhavere et al., https://doi.org/10.1016/j.radmeas.2007.12.002)
track etch detectors
(Benton and Richmond, https://doi.org/10.1016/1359-0189(86)90639-4)
