PILLE – Space Dosimetry Equipment
If there is a true Hungarian space industry success story, the Pille dosimeter is it. It is a work that began in the 1970s and continues today in the 21st century. The Pille is also a good example of how, in the increasingly important and global space industry, even a small country can make a big difference.
The start of the Pille journey
In the rivalry between the two great powers of the time, the conquest of space was a new chapter. Both the US and the Soviet Union were keen to take their parts in extra-terrestrial exploration, demonstrating the supremacy of their power of rule. Already in the 1960s, the Soviets wanted to cooperate with the socialist countries which were in their sphere of interest, to channel in the best engineer specialists and drain the existing relevant industry knowledge. Therefore, the Chairman of the Council of Ministers of the USSR, Alexei Nikolayevich Kosygin, announced the Interkosmos programme. Hungary formally joined the international cooperation in 1967, and in 1970, the Vertyikal-1 rocket was already carrying micrometeorite traps assembled by Hungarian engineers of the predecessor of the Centre for Energy Research.
In July 1976, Hungary stepped up a level, as they began preparing the first Hungarian astronaut for a joint space mission with the Soviets. The big event took place in 1980 when astronaut Bertalan Farkas went into space aboard the Soyuz-36 spacecraft.
However, he did not go empty-handed!
Pille is born
Human spaceflight is still not an everyday event, but back in those times, humanity knew even less about the effects of deep space radiation on the human body. It was already known that astronauts were exposed to radiation, but the dose could only be determined after they returned from space. There was a technical reason for this: the instruments measuring radiation were too large to be installed in spacecraft with volume capacity constraints. Once the astronauts returned, the radiation exposure of the space passengers had to be measured in a separate laboratory which was a time-consuming and complicated task. To measure this exposure, astronauts took a capsule with them which "absorbed" the radiation together with the astronauts and then the experts could measure the radiation with the help of this device. However, this did not answer the question of what the distribution of the astronaut's exposure looked like over time. There was a need for an instrument in the spacecraft that could measure in regular intervals and in real-time.
The Hungarian experts came up with a solution to this problem: the Pille dosimeter.
(The meaning of Pille in Hungarian is lightweight.)
The Pille is a thermoluminescent (TL) dosimetry system. The thermoluminescent system consists of a dosimeter and a dosimeter reader. When the TL dosimeter is exposed to radiation and then subsequently gets heated, the dosimeter emits a quantity of light proportional to the dose of radiation.
The engineers at the Central Institute for Physical Research have put together a system that has been experimented with since the second half of the 1960s. In the 1970s, Soviet experts commissioned the Hungarians to develop a dosimetry system that would meet the following requirements:
- the mass should be less than 1 kg,
- its size should not exceed 1 dm3,
- its average power consumption should not exceed a few watts,
- withstand the rough launch vibrations and hard docking of the time.
Challenges that Pille faced
What is the advantage of this construction? Access to more accurate radiation data, given the dosimeter holder, was sewed into the astronauts' clothing on Earth and read out after the astronaut's return (even after a year). With this solution, it was possible to make the measurements at the place of radiation, in the spacecraft, i.e. in space - which became important to determine the impact of exposure on health. In addition, one of the components of the device was the portability during spacewalks, making it possible to measure doses both inside and outside the spacecraft.
The main difficulty in this construction was the miniaturised size. For example, to measure the light coming out of the dosimeter, a detector with a small geometric size was needed, which would work efficiently even with a small mass. In addition, the anticipated use also presented the designers with several obstacles, which led to the use of miniature felt shock absorbers in the Pille to absorb the expected physical impact on the instrument.
Bertalan Farkas makes history with the Pille
As we mentioned, the first Hungarian astronaut took the very first Pille with him to test it in real life. (During the short journey - on the first and last day - a total of six experiments took place: Dose Experiments with the Pille, Work Capability, Interferon, Ötvös, Bealuca and Biosphere). The Hungarian team was anxiously awaiting the results, but then they were quickly relieved: the data read on the radio met expectations for both the nullified and the irradiated dosimeters.
Therefore, the first tests with the Pille equipment ended up with success.
The Pille continues to conquer
The development programme had not stopped at that point. NASA also placed an order for a battery-powered version, contrary to Soviet requests for safety reasons. Interestingly, the mechanically and electronically rebuilt Pille was used by the first female US astronaut, Sally Ride, on the Challenger-6 space shuttle in 1984.
A microprocessor-based version with a memory card was soon available, allowing even more measurements to be made, and was used by astronaut Thomas Reiter when he carried out a dosimetric mapping of the Mir station and a series of high-resolution time measurements onboard the station during the Euromir'95 mission in 1995. This revealed that astronauts on the orbiting space station were exposed to extra radiation above the so-called South Atlantic Anomaly.
The Pille goes international
The destruction of the Mir space station in 2001 was followed by the International Space Station (ISS), which is still in operation today. Hungary's contribution was the Pille, one of which was designed for the US Destiny module and another for the Russian Zvezda.
(The Hungarian space device was to have an even greater career as NASA wanted to make it part of the radiation protection system, but this was probably foiled by political reasons.)
The Pille'97, the third generation of the original construction, was launched on the ISS in 2001. In four and a half months, the American astronaut Jim Voss carried out almost 1700 successful measurements.
Since 2003, another piece of equipment has been sent to the Russian segment of the space station, where measurements are still being taken. In 2018, a new reader was sent to the Zvezda module, continuing a 40-year-long success story.
REMRED is now involved in the production of the fourth generation, and the development of the fifth generation of the Pille and is developing a dosimeter that no longer requires a readout device.
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