Radiation shielding experiment for CubeSat on highly elliptical orbit

The Van-Allen radiation belts around Earth have so far prevented CubeSats from operating on higher orbits despite the multitude of space physics that could be observed there.
CubeSats usually rely on radiation-sensitive commercial off-the-shelf components, but shielding options for CubeSats are limited due to their strict mass and size requirements. Optimised shielding is required, but so far, there have been no in-situ measurements of the performance of CubeSat shielding in the Van-Allen belts.
Foresail-2 is a 6U CubeSat proposed to measure the dynamics of the radiation belts on a highly elliptical orbit. For this purpose, it will carry a magnetometer, a plasma tether and a particle telescope for relativistic electrons and protons. The proposed geostationary transfer orbit intersects the Van-Allen belts. Despite the harsh radiation environment, Foresail-2 will attempt to make extended use of commercial off-the-shelf components, planned to be shielded by a 6 mm thick aluminium enclosure. RadFET sensors are proposed to monitor ionising dose rates inside the spacecraft.
Additional to the primary scientific instruments, a Radiation Experiment (RadEx) is proposed for Foresail-2 to measure the ionising dose behind five thicknesses of aluminium shielding and four alternative shielding materials, including multilayer shielding. RadEx is still in an early stage of development, but the current plans are to use the RadFET sensors Varadis VT01 and VT05 behind cutouts in the shielding of the satellite. The five different aluminium thicknesses are 0, 1, 2, 4 and 6 mm. The alternative materials are proposed to be Polyethylene, Polyethylene on top of tungsten, FR4, FR4 covered with solder on the back side and an aluminium chip for comparison. The RadFET sensors will be read out at least once per day by an ATmegaS64M1 microcontroller, which reports the readings to the onboard computer of the spacecraft.
In addition to the ionising dose measurements, RadEx will contain a shielding cutout for a Hercules RM48L952 processor to measure single-event effect rates in an elevated radiation environment. For this purpose, the processor will run codes to detect bit flips in its registers and memory. The ATmegaS64M1 microcontroller will monitor the Hercules RM48L952, which will be purely a device under test.
RadEx is being developed at Aalto University by a team of doctoral and master-level students. Foresail-2 is scheduled to launch in 2025, and RadEx will undergo total ionising dose testing at a Cobalt-60 source and single event effect testing at a proton beam or heavy ion test facility.
The main results of RadEx will be comparable measurements of the performance of CubeSat shielding, which can be used to design optimised shielding solutions for future CubeSat missions with elevated radiation requirements.