  Prepared for the 2014 ISAPP summer school, this review is focused on
space-borne and balloon-borne cosmic-ray and gamma-ray detectors. It is meant
to introduce the fundamental concepts necessary to understand the instrument
performance metrics, how they tie to the design choices and how they can be
effectively used in sensitivity studies. While the write-up does not aim at
being complete or exhaustive, it is largely self-contained in that related
topics such as the basic physical processes governing the interaction of
radiation with matter and the near-Earth environment are briefly reviewed.
