X-ray telescope

An X-ray telescope (XRT) is a telescope that is designed to observe remote objects in the X-ray spectrum. X-rays are absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, or satellites.

The basic elements of such a telescope are the optics (focusing or collimating) that collect the radiation entering the telescope, and the detector, with which the radiation is collected and measured. A variety of different designs and technologies have been used for these elements.

Many X-ray telescopes on satellites are compounded of multiple small detector-telescope systems whose capabilities add up or complement each other, and additional fixed or removable elements (filters, spectrometers) that add functionalities to the instrument.