Now calling at the International Space Station

On 31 July, an unmanned Russian Progress spacecraft was launched from the desert steppe of Kazakhstan. Its destination: the International Space Station (ISS). On board: five Timepix detectors developed by the Medipix2 Collaboration.


With the Timepix on board, Progress 48 was launched 31 July from the Baikonur Cosmodrome in Kazakhstan. Source: RSC Energia.

Timepix detectors are small, USB powered particle trackers based on Medipix2 technology. The Timepix chip, which was developed at CERN, is coupled to a silicon sensor and incorporated into a minature readout system - developed at IEAP, Prague - which is about the size of a USB pen drive. These systems have been used across a variety of disciplines: from the study of cosmic rays to biomedical imaging. Now on board the ISS, they are providing highly accurate measurements of space radiation for dosimetry purposes.

“There’s nothing else in the world that has quite the capability of Timepix detectors to identify individual particle tracks,” says Lawrence Pinsky, a member of the Medipix2 Collaboration who drove the push to get the Timepix detectors into space. “The ISS Timepix detectors will gather data to characterise the radiation field as a function of time, taking precise measurements of the spectrum of charge and velocity of particles present inside the  spacecraft.”

Among the many types of radiation measured by the ISS Timepix detectors will be heavy-ion radiation. Heavy ions are naturally seen only in space, although they can be found on Earth in accelerators and cancer treatment facilities. While the effects of acute exposure – that is, exposure to heavy doses over very short periods of time – to heavy-ion radiation are relatively well understood, the effect of chronic exposures is still unclear.

Progress 48 approaches the ISS, docking less than 24 hours after takeoff. Source: NASA TV.

“We know that heavy ions – the bare nuclei that are rattling around in space – are hugely more effective at causing long-term health risks per unit of energy,” explains Lawrence. “But assessing the full extent of these risks is difficult. Studies have been conducted at heavy ion treatment facilities using cell cultures, but they are historically unreliable when transferred to implications for humans.”

By measuring the baseline characteristics of heavy ion radiation, the ISS Timepix detectors will help radiation experts understand the nature of the exposure to astronauts, as well as the potential long-term side effects of heavy-ion cancer therapy. “Part of the beauty of Medipix technology is that the radiation measurements are completely independent of any particular dosimetric endpoint and can be converted for any type of future endpoints that may be adopted,” says Lawrence.

Though their trip off-planet has only just begun, NASA has already approved Timepix detectors to fly on the first test flight of the Orion module - part of the next generation of manned US spacecraft. Take-off is scheduled for 2014, giving the Medipix3 Collaboration the chance to improve their detectors even further. “This first trip to the ISS is an opportunity for us to get some real experience using the detectors in space, driving the development of the next generation of Timepix,” concludes Lawrence.

by Katarina Anthony