A large part of space radiation is composed of protons and heavy ions. At the lower altitudes of supersonic transports (SST) the situation is different because only a small number of heavy nuclei are still present and their interactions in the atmosphere generate fragmentations and induced neutrons. A dose equivalent meter based on microdosimetric techniques, named CIRCE, was used for real-time determination of the quality factor and dose equivalent in the stratosphere during aircraft flights at different altitudes and latitudes. The response of the system to high energy ions was tested with 320 MeV/amu C-12 ions at DUBNA Synchrocyclotron (Russia). The dose equivalent rates are in the 8.4-17.2 mSv.h-1 range, and the total quality factors are in the 1.53-2.20 range.

Since Dec 1988, date of the French-Soviet joint space mission "ARAGATZ", the CIRCE device (Compteur Intégrateur de Rayonnement Complexe dans l'Espace) had recorded dose equivalent and quality factor inside the MIR station (380-410 km, 51.5 degrees). After the initial gas filling two years ago, the low pressure tissue equivalent proportional counter is still in good working conditions. Some results of three periods, viz Dec 1988, Mar-Apr 1989 and Jan-Feb 1990 are presented. The average dose equivalent rates measured are respectively 0.6, 0.8 and 0.6 mSv/day with a quality factor equal to 1.9. Some detailed measurements show the increasing of the dose equivalent rates through the SAA and near polar horns. The real time determination of the quality factors allows to point out high LET (Linear Energy Transfer) events with quality factors in the range 10-20.

During the French-Soviet space mission "Aragatz," the experiment CIRCE (Compteur Integrateur de Rayonnement Complexe dans l'Espace) recorded the dose rate and quality factor values inside the MIR station. This paper presents results obtained with a new active dose equivalent meter based on microdosimetric techniques and using a low pressure tissue equivalent proportional counter. In terms of lineal energy CIRCE device works in the 0.2-1200 keV micrometer-1 range in tissue. Preliminary studies were performed in photon, neutron and heavy ion beams, and in the real stratosphere cosmic radiation field. Long term measurements on-board MIR station from December 1988 to April 1989 gave an average quality factor value equal to 1.9 +/- 0.3. Through the South Atlantic Anomaly (SAA), the quality factor was equal to 1.4. The temporal orbital variations of the dose rates and quality factors have been established in space dosimetry for the first time.

Iodide can reduce radioactive iodine thyroid uptake and whole-body irradiation. Maximal effectiveness is obtained when 3 conditions are fulfilled: adequate dosage: potassium iodide 130 mg (i.e. iodide 100 mg) as tablets in adults and older children, 50 mg in infants under one year of age; prompt administration after contamination and daily treatment as long as the contamination persists. Depending on the importance and duration of the contamination, different dosages may be required. In any case, children must be given priority for prophylactic measures.