This list of space telescopes (astronomical space observatories) is grouped by major frequency ranges: gamma ray, x-ray, ultraviolet, visible, infrared, microwave and radio. Telescopes that work in multiple frequency bands are included in all of the appropriate sections. Space telescopes that collect particles, such as cosmic ray nuclei and/or electrons, as well as instruments that aim to detect gravitational waves, are also listed. Missions with specific targets within the Solar System (e.g. the Sun and its planets), are excluded; see List of Solar System probes for these, and List of Earth observation satellites for missions targeting Earth. Two values are provided for the dimensions of the initial orbit. For telescopes in Earth orbit, the min and max altitude are given in kilometers. For telescopes in solar orbit, the minimum distance (periapsis) and the maximum distance (apoapsis) between the telescope and the center of mass of the sun are given in astronomical units (AU). Gamma ray Gamma ray telescopes collect and measure individual, high energy gamma rays from astrophysical sources. These are absorbed by the atmosphere, requiring that observations are done by high-altitude balloons or space missions. Gamma rays can be generated by supernovae, neutron stars, pulsars and black holes. Gamma ray bursts, with extremely high energies, have also been detected but have yet to be identified. X-ray X-ray telescopes measure high-energy photons called X-rays. These can not travel a long distance through the atmosphere, meaning that they can only be observed high in the atmosphere or in space. Several types of astrophysical objects emit X-rays, from galaxy clusters, through black holes in active galactic nuclei to galactic objects such as supernova remnants, stars, and binary stars containing a white dwarf (cataclysmic variable stars), neutron star or black hole (X-ray binaries). Some Solar System bodies emit X-rays, the most notable being the Moon, although most of the X-ray brightness of the Moon arises from reflected solar X-rays. A combination of many unresolved X-ray sources is thought to produce the observed X-ray background. Ultraviolet Ultraviolet telescopes make observations at ultraviolet wavelengths, i.e. between approximately 10 and 320 nm. Light at these wavelengths is absorbed by the Earth's atmosphere, so observations at these wavelengths must be performed from the upper atmosphere or from space. Objects emitting ultraviolet radiation include the Sun, other stars and galaxies. UV ranges listed at Ultraviolet astronomy#Ultraviolet space telescopes. Visible light The oldest form of astronomy, optical or visible-light