XMM-Newton is a European Space Agency (ESA) X-ray observatory launched in 1999. It is designed to study high-energy phenomena in the universe, such as black holes, neutron stars, and supernovae.

The Chandra X-ray Observatory is NASA's flagship X-ray observatory. It was launched in 1999 and is designed to study a wide range of astronomical objects, including black holes, neutron stars, supernovae, and galaxy clusters.

Suzaku is an X-ray observatory launched by the Japan Aerospace Exploration Agency (JAXA) in 2005. It is designed to study the hot, diffuse gas in the universe, as well as black holes and neutron stars.

Insight-HXMT is an X-ray observatory launched in 2012 as part of the Chinese Academy of Sciences' Hard X-ray Modulation Telescope (HXMT) mission. It is designed to study high-energy phenomena in the universe, such as black holes, neutron stars, and supernovae.

Astrosat is an X-ray observatory launched by the Indian Space Research Organisation (ISRO) in 2016. It is designed to study a wide range of astronomical objects, including black holes, neutron stars, supernovae, and galaxy clusters.

eROSITA is an X-ray observatory launched in 2017 as part of the Russian Federal Space Agency's Spektr-RG mission. It is designed to study the hot, diffuse gas in the universe, as well as black holes and neutron stars.

IXPE is an X-ray observatory launched by NASA in 2018 as part of the Imaging X-ray Polarimetry Explorer (IXPE) mission. It is designed to study the polarization of X-rays from astronomical objects, which can provide information about their magnetic fields and the geometry of their emission.

Athena is an X-ray observatory planned to be launched by the European Space Agency (ESA) in 2023. It is designed to study the hot, diffuse gas in the universe, as well as black holes and neutron stars.

Swift is an X-ray observatory launched by NASA in 2004 as part of the Swift Gamma-Ray Burst Mission. It is designed to study gamma-ray bursts and other transient phenomena in the universe.

ROSAT is an X-ray observatory launched in 1990 as part of the German Aerospace Center's ROSAT mission. It was the first X-ray observatory to perform a complete survey of the entire sky in X-rays.

HEAO-1 is an X-ray observatory launched by NASA in 1978 as part of the High Energy Astronomy Observatory (HEAO) program. It was the first X-ray observatory to be placed in a high Earth orbit.

ASCA is an X-ray observatory launched in 1993 as part of the Japanese Institute of Space and Astronautical Science's ASCA mission. It was the first X-ray observatory to have a large collecting area and a high energy resolution.

STIS is an X-ray observatory launched by NASA in 1999 as part of the Space Telescope Imaging Spectrograph (STIS) mission. It is designed to study the composition and physical properties of astronomical objects.

XMM-Newton is an X-ray observatory launched in 2000 as part of the European Space Agency's XMM-Newton mission. It is designed to study a wide range of astronomical objects, including black holes, neutron stars, supernovae, and galaxy clusters.

Swift is an X-ray observatory launched by NASA in 2004 as part of the Swift Gamma-Ray Burst Mission. It is designed to study gamma-ray bursts and other transient phenomena in the universe.