When cosmic rays hit the top of Earth’s atmosphere, they create a spray of secondary radiation that rains down on the planet below. For years, the students of Earth to Sky Calculus have been measuring secondary cosmic rays on airplanes and high-altitude balloons using two types of sensors.

First, are the neutron bubble chambers:

Each bubble pictured above is formed by an energetic neutron (200 keV – 15 MeV) passing through the chamber. Counting bubbles yields the total dose. We use chambers manufactured by Bubble Technology Industries Inc. of Canada.

Second, we monitor X-rays and gamma rays using sensors based on Geiger tubes:

These are Polimaster 621M dosimeters sensitive to X-rays and gamma-rays. They sample energies between 10 keV and 20 MeV, spanning the range of medical X-ray machines, airport security devices, and “killer electrons” in Earth’s radiation belts.

Cosmic rays are a cocktail of different things: e.g., neutrons, protons, pions, electrons, X-rays, and gamma rays spanning a wide range of energies. Our sensors sample only three ingredients of that cocktail: neutrons, X-rays, gamma-rays. Furthermore, we are sampling only a relatively low range of energies. Many cosmic rays are much more energetic than the 15 MeV to 20 MeV upper limit of our detectors.

This means our data are only the tip of the iceberg.  Flight crews and passengers absorb even more radiation than we can detect.