The Swift XRT contains a grazing incidence Wolter I telescope to focus X-rays onto a state-of-the-art CCD. The complete mirror module for the XRT consists of the X-ray mirrors, thermal baffle, a mirror collar, and an electron deflector. To prevent on-orbit degradation of the mirror module's performance, it is maintained at 20 ± 5 °C, with gradients of <1 °C by an actively controlled thermal baffle (purple, in schematic below) similar to the one used for JET-X. A composite telescope tube holds the focal plane camera (red), containing a single CCD-22 detector.
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, XRTs must be mounted on high altitude rockets or artificial satellites. The telescopes have varying directionality or imaging ability based on glancing angle reflection rather than refraction or large deviation reflection. The most common methods of design are grazing incidence mirrors and coded apertures. The limitations of X-ray optics result in much narrower fields of view than visible or UV telescopes. A recent innovation in telescope design uses normal incidence reflective multilayer optics.
