XMM

XMM, short for X-ray Multi-Mirror Mission (XMM-Newton), is an X-ray space observatory built and operated by the European Space Agency (ESA). Launched in December 1999, it was designed to study the high-energy universe, including accreting black holes, neutron stars, galaxy clusters, and the hot intergalactic medium. The mission is noted for its combination of imaging, spectroscopy, and multi-wavelength capability.

The payload comprises three X-ray telescope modules and an optical/UV monitor. Each telescope uses nested Wolter type I mirrors to focus X-rays onto detectors. The X-ray instruments aboard XMM-Newton include the European Photon Imaging Camera (EPIC), which consists of two MOS CCD cameras and one PN CCD camera, and the Reflection Grating Spectrometer (RGS) for high-resolution X-ray spectroscopy. The Optical Monitor (OM) provides simultaneous optical/UV data. The observatory covers roughly 0.1 to 12 keV in X-ray energy, with complementary optical/UV coverage from the OM.

XMM-Newton operates in a highly elliptical Earth orbit, with a perigee of a few thousand kilometers and an apogee around 100,000 kilometers, enabling long, nearly uninterrupted observing times away from the radiation belts. Although planned for a limited mission life, it has been extended repeatedly and remains in operation, with data publicly released through the XMM-Newton Science Archive.

Scientific impact of XMM-Newton includes extensive studies of accreting black holes and active galactic nuclei, the properties of hot gas in groups and clusters of galaxies, and the cosmic X-ray background. It has produced large catalogs of serendipitous X-ray sources and contributed to deep surveys that complement other X-ray observatories such as Chandra and ROSAT.