The book discusses the main issues of spectrometry of ionizing radiation in outer space. Overview data on characteristics of streams of charged particles and electromagnetic radiation in space, which are the object of measurement, are given. The basic principles of building spectrometers of various types of radiation, methods for performing spectrometers of charged particles of low and medium energies, X-ray and y-radiation necessary for conducting research in near-Earth space, in other planets, in X-ray and y-astronomy are considered.