The Earth’s magnetic field is capturing energetic charged particles (solar wind and cosmic rays = galactic radiation) in two belts round the Earth. These, mostly electrons and protons, are trapped in the two belts, thus the belts are preventing the Earth from these hostile particles. James Van Allen has discovered in the middle of the 20th century these Earth´s belts, which are later known as the Van Allen Belts.
Located at the inner magnetosphere of the Earth, the inner belt starts at an altitude of about 1000 km and expands up to 6000 km. The outer belt starts roughly at 13000 km and expands up to 60000 km.
In general, space missions try to avoid touching or flying through the Van Allen Belt or try crossing through the belts as quickly as possible. The reason for this are the significantly increased levels of radiations which causes problems and damage to electronic systems and can even result in a total loss of the space-craft.
The CLIMB mission has exactly those regions as its mission targets. Major objective is to assess the survivability of CubeSat technology in such problematic region and taking scientific data.