In-flight measurements of radiation fields and doses.

The cosmic ray field at civil aviation altitudes consists of low-ionising radiations and neutrons with different energies. At the meeting on radiation exposure of civil air-crew held in Luxembourg in 1991, it was pointed out that there was a need to obtain a better evaluation of the dose with special regard to that of high energy neutrons. This problem has been tackled within the multinational research programmes of the Commission of the European Communities. These research activities made it possible to set up and calibrate the most advanced systems for the assessment of the occupational exposure of aircraft crew. In particular, two advanced neutron spectrometers have been developed, which cover the entire energy range of neutrons. Under the CEC contracts, a large variety of data has been gathered on many longhaul flights, using different dosimetric systems. Since most of the data have been gathered during the period of solar minimum (1994-1997) they represent an upper limit of the dose due to galactic cosmic rays.