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This article is about X-ray telescope. For gravitational wave detector, see Einstein Telescope.
Einstein Observatory (HEAO-2) was the first fully imaging X-raytelescope put into space and the second of NASA's three High Energy Astrophysical Observatories. Named HEAO B before launch, the observatory's name was changed to honor Albert Einstein upon its successfully attaining orbit.
The Einstein Observatory, HEAO-2, was launched on November 13, 1978, from Cape Canaveral, Florida, on an Atlas-Centaur SLV-3D booster rocket into a near-circular orbit with an initial altitude slightly above 500 km. Its orbital inclination orbit was 23.5 degrees. The Einstein Observatory satellite re-entered the Earth's atmosphere and burned up on March 25, 1982.
The Einstein Observatory carried a single large grazing-incidence focusing X-ray telescope that provided unprecedented levels of sensitivity (hundreds of times better than previously achieved) and arc-second angular resolution of point sources and extended objects. It had instruments sensitive in the 0.2 to 3.5 keV energy range. A collection of four focal-plane instruments was installed in the satellite: 
HRI, or High Resolution Imaging camera, 0.15-3 keV
IPC, or Imaging Proportional Counter, 0.4 to 4 keV
Payloads are separated by bullets ( · ), launches by pipes ( | ). Manned flights are indicated in bold text. Uncatalogued launch failures are listed in italics. Payloads deployed from other spacecraft are denoted in (brackets).
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