Countless bright dots and streaks scattered across a black and white chequerboard background, each one representing a high-energy particle interacting with the image sensor that captured the photo.
Three years ago, the European Space Agency’s shoebox-sized TRISAT-R CubeSat, developed by the University of Maribor in Slovenia, tested an extremely miniaturised imaging technology in space.
This tiny camera – about the size of a 20 cent coin’s edge – managed to snap an image of Earth, while having to endure the harsh environment of medium Earth orbit, where highly energetic – typically meaning very fast – particles dart through the vacuum of space in all directions.
Developed as part of an ESA General Support Technology Programme (GSTP) activity, the TRISAT team’s miniaturised imaging system was recently tested in CERN’s CHARM facility to explore its potential for spacecraft attitude and orbit determination.
The highly accelerated radiation campaign, enabled through the RADNEXT project, exposed the miniature camera to an intense mixed-field particle environment covering a broad spectrum of particles and energies relevant to space applications. In CHARM, the camera faced conditions associated with radiation trapped by Earth’s magnetic field or emitted by the Sun during solar particle events.
“Our tiny imaging system spent more than 108 hours in the CHARM chamber, exposed to a mixed-field radiation environment containing high-energy particles, including hadrons such as protons, neutrons and pions,” explains Iztok Kramberger, principal investigator of the TRISAT programme at the University of Maribor.
“The camera, pointed at a 13 cm wide chequerboard which served as a reference pattern, acquired over 4 million images at a rate of 10 frames per second. Of these, we kept more than 160 000 images for detailed analysis to study radiation-induced pixel activation and the subsequent recovery of the image sensor following particle interactions.”
The images are speckled with white dots and streaks called ‘radiation-induced artefacts’. Each one is caused by an energetic particle traversing the image sensor, illustrating the challenges that imaging systems face when operating in harsh radiation environments like space.
“For this test we have joined forces with SkyLabs, who implemented protection mechanisms into the camera system to make sure the intense radiation doesn’t cause any permanent damage or loss of functionality,” adds Iztok.
“By analysing the large dataset acquired during this campaign, we are investigating the frequency and spatial distribution of radiation-induced artefacts, the number of pixels affected by each event, how and when affected pixels recover, and how to distinguish transient, recoverable effects from permanent radiation-induced damage. These insights will support the development of more robust image processing algorithms and enhance next-generation attitude and orbit determination technologies.”
[Image description: The image shows a square with a black-and-white chequered pattern. Bright dots and streaks speckle the image. In the centre of the pattern, a white square appears brighter than the others.]