Why are satellites and space probes useful for observing cosmic rays?

Satellites and space probes are essential for observing cosmic rays because they allow scientists to study "primary" cosmic ray particles directly before they interact with Earth’s atmosphere.1

When primary cosmic rays reach the outer edge of the atmosphere, they collide with atmospheric nuclei, creating "secondary" particles—such as muons and neutrons—that reach the surface. Because these collisions alter the original particles, ground-based observations cannot provide a direct look at the primary cosmic rays themselves. By placing instruments in orbit or utilizing long-range probes, researchers can bypass the atmosphere’s filtering effect to detect and analyze the primary particles in their original state.21