XMM optical design

The optical design of ESA's XMM observatory illustrated by one of the three mirror modules. The optical design not only provides high throughput and large bandwidth, but also achieve the medium-resolution goal of 20-30 arcsec on-axis. The high throughput is achieved by nesting a large number of Wolter-1 shells, as shown in the figure. The X-ray telescope uses the principle of grazing-incidence (at about 0.5deg) X-ray reflection to reflect and image the X-rays from gold-coated paraboloid and hyperboloid surfaces (see inset). The other two main parts of the X-ray payload elements are a CCD array (EPIC) and a reflection-grating spectrometer (RGS), which fit behind each mirror module. The CCD array is the prime-focus camera, which will perform the mission's broadband (0.1-10 keV) imaging and spectroscopically resolve the helium-like and hydrogenic K lines from most of the abundant elements. [Image Date: 01-02-97] [97.12.016-001]