Proba-V - From CERN to space


As ESA's Proba-V minisatellite monitors terrestrial vegetation, it will also survey the space surrounding itself. A new detector chip based on technology first developed for CERN's Large Hadron Collider is carried on the satellite's exterior to measure space radiation.

Less than a cubic metre in volume, Proba-V is hosting five additional technology experiments along with its main vegetation-monitoring payload. These include two radiation instruments to sample the charged particles the minisatellite will encounter across its orbit.

The larger of the pair is the wide-view Energetic Particle Telescope built by a consortium led by QinetiQ Space in Belgium, the satellite's prime contractor.

In addition, a smaller instrument based on a 'Timepix' chip complements the main radiation detector. "The flight on Proba-V will be the first time this chip is exposed to outer space," says Zdenk Kozaek of the Czech Research Centre (CSRC), prime contractor for the SATRAM (Space Application of Timepix-based Radiation Monitor) payload.

Timepix uses a 256 x 256-pixel silicon sensor. The pixels - each about 55 micrometres square, around half the thickness of an average human hair - incorporate individual signal electronics, making them sensitive to individual quanta of ionising radiation.

The chip's origin goes back to deep underneath the Swiss-French border: CERN needed a detector with sufficient sensitivity and dynamic range to gather snapshots of what would be coming from the Large Hadron Collider when it became operational.

"Having developed this technology, the Medipix collaboration was established to expand its usage outside the high energy physics field," explains Zdenek Vykydal of the Institute of Experimental and Applied Physics of the Czech Technical University of Prague (IEAP CTU), partnering with CSRC for SATRAM.

"The starting point was to apply it to X-ray radiography, but this state-of-the-art detector has turned out to be so powerful and flexible, the range of applications is really large. "It's been used for everything from composite materials testing to imaging insect bodies, from neutron tomography to examining antique paintings."

A prominent member of the Medipix consortium, IEAP CTU has previously developed read-out interfaces, data acquisition and processing software for the family of chips, as well as advanced calibration methods.

This technology's potential for space was clear, adds Carlos Granja of IEAP CTU: "Precise particle track pattern analysis - like reconstructing a road accident from skid marks - allows identification of the types and energies of charged particles, as well as tracing back their trajectories to provide a sky mapping of their source of origin.

"Working with NASA and the University of Houston, these same chips are already flying in space, serving as highly miniaturised dosimeters for crewmembers of the International Space Station, though these are installed inside pressurised modules rather than outside in open space."

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