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RAMONA: Radiation Monitoring ON board Aircraft


With the implementation of the new Radiation Protection Ordinance in 2001, the EU Directive 96/29/EURATOM, which had been in force for some time already, was integrated into national law. This brought about that flying personnel is now considered as occupationally exposed to radiation. In Germany, approx. 30000 persons are concerned. The radiation field at aircraft altitudes in the atmosphere is caused by cosmic radiation coming from outer space. Due to the variety of secondary particles (neutrons, protons, electrons, etc.) and the high energies which are sometimes generated, only few detection systems are suitable for dose measurements in this radiation field. Since 1997 already, PTB has been carrying out measurements on board aircrafts. Thereby, a measurement system was developed which is accommodated in an attaché case (the so-called "pilot case"). The dosimeter used is a commercially available tissue-equivalent proportional counter. Even in such complex radiation fields, it is able to measure approximately the absorbed dose, i.e. the energy which is transmitted into human tissue. By using corresponding conversion factors, this allows us to calculate the ambient dose equivalent or the exposure rate. The pilot case has been mounted on board a Lufthansa Airbus and could thus record measurements worldwide between December 2003 and September 2004; the Airbus, however, only flew within the Northern hemisphere. The measured data allowed us to obtain easily applicable mathematical functions which describe the ambient equivalent dose rate depending on the latitude and the longitude.

The RAMONA project funded by the Federal Ministry of Transport, Building and Urban Affairs goes one step further. The University of Kiel, the Technical University of Braunschweig, DLR in Cologne, PTB, LTU and Lufthansa have formed a partnership aiming at integrating dosimeters into commercial aircrafts in order to measure the exposure to radiation over a longer period. The investigation of so-called "solar particle events" is of particular interest. These are solar eruptions in the course of which high-energy protons are emitted by the sun so that it can come to a considerable increase in the dose observed at aircraft altitudes.

Contrary to the pilot case, significantly smaller dosimeters or radiation detectors are to be used within the scope of RAMONA. For this purpose, the measuring system NAVIDOS (see Figure) has been developed in cooperation with the University of Kiel. On the basis of the DOSTEL detector, which has been proven and tested in outer space, NAVIDOS is, thanks to a high-sensitivity GPS sensor and an extremely strong antenna, able to receive GPS data in every spot of the passenger cabin of the aircraft. This allows us to determine the flight coordinates nearly independent of the point of installation. The data logger developed in Department 6.4 was modified into a central data evaluation unit. All measuring data (counting rates, dose rates, cabin pressure, GPS) are saved to an SD memory card which must be exchanged once a month. A first test on board aircrafts has confirmed the functionality of the system. Lufthansa is also working intensively on mounting NAVIDOS into an Airbus A340.

Figure : The NAVIDOS system with a size of 17 x 17 x 12 cm3 and a weight of approx. 4 kg is very compact. The OLED display allows us to immediately check the measurement. The SD memory card is located above the green LED; the GPS antenna is visible on the lid of the device.