Focusing diffraction optics for orbital telescopes

The review is devoted to the principles, state of the art and problems of diffractive optics used to focus X-ray and $\gamma$-radiation in telescopes at orbital stations. Various multilayer structures for normal incidence telescopes, supermirrors for Wolter optics, Laue lens as a soft $\gamma$-radiation concentrator, as well as modified Fresnel zone plates for focusing radiation in a wide energy range with an unprecedented high angular resolution (10$^{-1}$–10$^{-3''}$).