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The Third Small Astronomy Satellite (SAS-3)

artist concept of SAS-3
Credit: NASA

The third US Small Astronomy Satellite (SAS-3) was launched in May 1975, with 3 major scientific objectives: 1) determine bright X-ray source locations to an accuracy of 15 arcseconds; 2) study selected sources over the energy range 0.1-55 keV; and 3) continuously search the sky for X-ray novae, flares, and other transient phenomena. It was a spinning satellite with pointing capability.

Mission Characteristics

* Lifetime: May 1975 - Apr 1979
* Energy Range: 0.1-60 keV
* Payload:
There are four X-ray experiments on SAS-3 that all used proportional counters as detectors with different collimating system. The experiments were not co-aligned.
  • Modulation collimators (2-11 keV)
  • Slat and Tube collimators (1 up to 60keV)
  • Low-energy detector system
    0.15-1.0 keV, 2.9° FOV
* Science Highlights:
  • Discovery of a dozen X-ray burst sources among which
    the Rapid Burster
  • First discovery of X-ray from an highly magnetic WD binary system, AM Her
  • Discovery of X-ray from Algol and HZ 43.
  • Precise location of about 60 X-ray sources
  • Survey of the Soft X-ray background (0.1-0.28 kev)
* Archive: Raw Data in their native format

[About SAS-3] ( [Archive] ( [Gallery] ( [Publications] (

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