Physicist Sam Ting spent years lobbying to put a
cosmic ray detector aboard the International Space Station.
Looking at contributions from galactic
cosmic rays, secondary particles, and sensor background, they were able to derive energy spectra for the radiation dose that humans or instruments would absorb in the lunar environment.
Cosmic rays are subatomic particles that move through space at almost the speed of light.
Twenty-four segmented telescopes watch the skies for faint streaks of ultraviolet fluorescence produced when nitrogen atoms are ionized by an incoming
cosmic ray. Meanwhile, 1,600 ground-level detectors --instrumented tanks of purefied water--detect "air showers" of secondary particles (mostly gamma rays and electrons) that are spawned when a high-energy
cosmic ray collides with an atom in the top of the atmosphere.
Researchers hope that AMS can bring clarity to this debate because of its leg up on other
cosmic ray detectors.
The detector provides high-precision measurements of
cosmic ray particle fluxes, their ratios and gamma rays.
As a result, even low-energy
cosmic rays can reach the surface, turning the Moon into a handy space-based particle detector.
The question arises: what energy could be
cosmic rays, if the distance between the source and the Earth would be much less than the Greisen-Zatsepin-Kuzmin limit, and could not microparticle produce a huge macroscopic effect?
Special detectors recorded by-products of the
cosmic ray known as muons that are only partially absorbed by stone and take noticeably different trajectories through air.
Lead scientist Professor Gregory Snow, from the University of Nebraska-Lincoln in the US, said: "There have been other pieces of evidence, but I would say this paper really confirms that most of the highest energy
cosmic ray particles are not coming from the Milky Way.