The objectives of this study are:

1. To better characterize the neutron environment aboard the ISS. Better understanding of the neutron contribution will assist in the development of more effective countermeasures. Neutrons are of particular interest to radiation health and protection as neutrons have higher radiation Quality Factor (QF) and since they have not been well characterized by operational monitoring. It has been recognized that neutrons make up a significant fraction (10-30%) of the biologically effective radiation exposure in low-Earth orbit (i.e. ISS).
2. To repeat the measurements from the RaDI - N1 study, which was conducted on early increments on the ISS, in the same/equivalent locations aboard the ISS: USLab, JEM (Nominal), COLUMBUS, and Node2 (Reserve). The additional data will increase the statistical accuracy of the neutron measurements and also allow comparison of neutron fields at different periods of the solar cycle.

The results of Radi-N 1 and 2 study will allow better understanding of radiation environment aboard the ISS. The utilization of newly developed Bubble Detector Spectrometer will help characterize the neutron spectrum on board, and measurements in different ISS locations will provide a means of assessing the neutron field symmetry in different modules of the Station. Measuring the average dose within different segments of ISS will help with development of radiation protection plan for future missions.

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