X-ray telescope

An X-ray telescope (XRT) is a telescope that is designed to observe remote objects in the X-ray spectrum. In order to get above the Earth's atmosphere, which is opaque to X-rays, X-ray telescopes must be mounted on high altitude rockets, balloons or artificial satellites. The basic elements of the telescope are the optics (focusing or collimating), that collects the radiation entering the telescope, and the detector, on which the radiation is collected and measured. A variety of different designs and technologies have been used for these elements. Many of the existing telescopes on satellites are compounded of multiple copies or variations of a detector-telescope system, whose capabilities add or complement each other and additional fixed or removable elements (filters, spectrometers) that add functionalities to the instrument. X-ray optics The most common methods used in X-ray optics are grazing incidence mirrors and collimated apertures. The utilization of X-ray mirrors allows to focus the incident radiation on the detector plane. Different geometries (e.g. Kirkpartrick-Baez or Lobster-eye) have been suggested or employed, but almost the totality of existing telescopes employs some variation of the Wolter I design. The limitations of this type of X-ray optics result in much narrower fields of view (typically