|Website||Einstein Observatory at NASA.gov|
|Mission duration||4 years|
|Dry mass||3,130 kilograms (6,900 lb)|
|Start of mission|
|Launch date||13 November 1978, 05:24UTC|
|Rocket||Atlas SLV-3D Centaur-D1AR|
|Launch site||Cape Canaveral LC-36B|
|End of mission|
|Last contact||17 April 1981|
|Decay date||26 May 1982|
|Perigee altitude||465 kilometres (289 mi)|
|Apogee altitude||476 kilometres (296 mi)|
|Epoch||13 November, 1978 05:24:00 UTC|
Einstein Observatory (HEAO-2) was the first fully imaging X-ray telescope 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
- SSS, or Solid State Spectrometer, 0.5 to 4.5 keV
- FPCS, or Bragg Focal Plane Crystal Spectrometer
There was also a coaxial instrument 'MPC', the Monitor Proportional Counter, working in the 1-20 keV range, and two filters that could be used with the imaging detectors:
- BBFS, Broad Band Filter Spectrometer (aluminium and beryllium filters than can be placed into the X-ray beam, to change the spectral sensitivity)
- OGS, Objective grating spectrometer (transmission gratings with a spectral resolution of about 50)
- "HEA Heritage Missions: Einstein Observatory". cfa.harvard.edu. Retrieved March 27, 2014.
- "Einstein Observatory (HEAO-2)". ecuip.lib.uchicago.edu. Retrieved March 27, 2014.
- Giacconi, R.; Branduardi, G.; Briel, U.; Epstein, A.; Fabricant, D.; Feigelson, E.; Forman, W.; Gorenstein, P.; Grindlay, J.; Gursky, H.; Harnden, F. R.; Henry, J. P.; Jones, C.; Kellogg, E.; Koch, D.; Murray, S.; Schreier, E.; Seward, F.; Tananbaum, H.; Topka, K.; Van Speybroeck, L.; Holt, S. S.; Becker, R. H.; Boldt, E. A.; Serlemitsos, P. J.; Clark, G.; Canizares, C.; Markert, T.; Novick, R.; et al. (1979). "The Einstein /HEAO 2/ X-ray Observatory". The Astrophysical Journal. adsabs.harvard.edu. 230: 540. Bibcode:1979ApJ...230..540G. doi:10.1086/157110. Retrieved March 27, 2014.
- HEAO Program
- High Energy Astronomy Observatory 1
- High Energy Astronomy Observatory 3
- Timeline of artificial satellites and space probes