Task Group 67
Radiation Protection in Space

Astronauts and Cosmonauts are living and working in low earth orbit (LEO) for extended periods of time, especially now during the construction, operation and maintenance of the International Space Station (ISS). The environmental radiation field they are exposed to in space is complex. the primary radiation field contains high- energy particles with unique high-LET components that are very different from the typical low- energy electron, photon and neutron radiation fields encountered in most occupational exposure environments on earth. In addition, the primary radiation produces secondary radiation of various types by interactions with material of the spacecraft and its internal equipment. The purpose of an operational radiation safety program for astronauts working in low earth orbit is to assess and control the radiation exposure of those individuals in a way that is compatible with the tasks of the mission and the prevailing radiation fields in orbit. The expected annual dose is of the order of several hundreds mSv/y, which is above the occupational dose limit. Exposure of astronauts in space was one of the occupational exposures from natural sources listed in ICRP Publication 60 (136), but no guidelines have been developed internationally.

Currently, different philosophies and approaches are followed for radiological protection in space in various countries or organisations. There is a need for ICRP to prepare guidance on this topic. This requires implementing the System of Radiological Protection for work and life in space, which includes optimization and may require the establishment of special dose levels for protection of these workers.

The basis for any guidance on radiological protection measures is a reliable assessment of the intensity of the radiation fields involved and the exposure of the astronauts.  This necessitates measurements of radiation fluences, particle energy spectra, absorbed dose and LET-distributions in combination with extended particle transport calculations.

This Task Group is dealing with questions of the assessment of radiation exposure of astronauts in space. The followings are the main discussion points:

• Analysis of the radiation field and its high-LET components in space
• Application of dose quantities
• Methods of dose estimation and detectors for space radiation
• Development of reference doses