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The Einstein Observatory (HEAO-2)

artist concept of HEAO-2
Credit: NASA

The second of NASA's three High Energy Astrophysical Observatories, HEAO-2, renamed Einstein after launch, was the first fully imaging X-ray telescope put into space. The few arcsecond angular resolution, the field-of-view of tens of arcminutes, and a sensitivity several 100 times greater than any mission before it provided, for the first time, the capability to image extended objects, diffuse emission, and to detect faint sources. It was also the first X-ray NASA mission to have a Guest Observer program.

Overall, it was a key mission in X-ray astronomy and its scientific outcome completely changed the view of the X-ray sky.

Mission Characteristics

* Lifetime: 12 November 1978 - April 1981
* Energy Range: 0.2 - 20 keV
* Special Features: First imaging X-ray telescope in space
* Payload:
  • A Wolter Type I grazing incidence telescope (0.1-4 keV).
    Four instruments could be rotated, one at a time, into the focal plane:
    • Imaging Proportional Counter (IPC; 0.4-4.0 keV)
      eff. area 100 cm2, FOV 75´, ~1 arcmin spatial resolution.
    • High Resolution Imager (HRI; 0.15-3.0 keV)
      eff. area 5 - 20 cm2, FOV 25´, ~2 arcsec spatial resolution.
    • Solid State Spectrometer (SSS; 0.5-4.5 keV)
      eff. area 200 cm2, FOV 6´, E/delta E of 3-25
    • Focal Plane Crystal Spectrometer (FPCS; 0.42-2.6 keV)
      eff. area 0.1 - 1.0 cm2, FOV 6´, 1´x20´, 2´x20´, 3´x30´, E/delta E of 50-100 for E < 0.4 keV, E/delta E of 100-1000 for E > 0.4 keV
  • Monitor Proportional Counter (MPC; 1.5 - 20 keV)
    eff. area 667 cm2, FOV 1.5°, energy resolution ~20% at 6 keV. Co-aligned with the X-ray telescope.
  • Objective Grating Spectrometer (OGS) : 500 mm-1 & 1000 mm-1, energy resolution dE/E ~ 50. Used in conjunction with HRI.
* Science Highlights:
  • First high resolution spectroscopy and morphological studies of supernova remnants.
  • Recognized that coronal emissions in normal stars are stronger than expected.
  • Resolved numerous X-ray sources in the Andromeda Galaxy and the Magellanic Clouds.
  • First study of the X-ray emitting gas in galaxies and clusters of galaxies revealing cooling inflow and cluster evolution.
  • Detected X-ray jets from Cen A and M87 aligned with radio jets.
  • First medium and Deep X-ray surveys
  • Discovery of thousands of "serendipitous" sources
* Archive: Catalogs, Spectra, Lightcurves, Images and Raw data

[About HEAO-2] ( [Archive] ( [Gallery] ( [Publications] (

Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

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All material on this site has been created and updated between 1997-2012.

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