Karl Bergwitz made early balloon measurements of atmospheric ionization, comparing the detector response at altitude with observations nearer the ground. These experiments tested expectations for radiation originating in the terrestrial environment.[ref]
100 Years of Cosmic Rays by DESY. First panel: balloon electrometer measurements and detector limitations
The experiment's value lies in changing the material between a proposed source and the detector. Interpretation also depends on instrumental behaviour under changing conditions, so altitude dependence must be separated from leakage, calibration changes and the detector's own background.
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