The HEAO-1 Satellite


artist concept of HEAO-1
Beginning in 1977, NASA launched a series of very large scientific payloads called High Energy Astronomy Observatories(HEAO). The first of these missions, HEAO-1 surveyed the X-ray sky almost three times over the 0.2 keV - 10 MeV energy band, provided nearly constant monitoring of X-ray sources near the ecliptic poles. More detailed studies of a number of objects were made through pointed observations lasting typically 3-6 hours.


Mission Characteristics

* Lifetime : 12 August 1977 - 9 January 1979
* Energy Range : 0.2 keV - 10 MeV
* Payload :
  • A1 - Large Area Sky Survey experiment (LASS) :
    0.25-25 keV, eff. area 7 modules each of 1350 - 1900 cm2, FOV varied between 1° X 4° to 1° x 0.5° for finest collimators.
  • A2 - Cosmic X-ray Experiment (CXE) :
    six separate proportional counters
    • Low Energy Detectors (LED) 0.15-3.0 keV, eff. area 2 detectors of 400 cm2 each
    • Medium Energy Detector (MED) 1.5-20 keV, eff. area 1 detector at 800 cm2
    • High Energy Detector (HED) 2.5-60 keV, eff. area 3 detectors at 800 cm2 each
    MED and HEDs had various FOV settings, 1.5° x 3°, 3° x 3° and 3° x 6°
  • A3 - Modulation Collimator (MC) :
    0.9-13.3 keV, eff. area 2 collimators 400 cm2 (MC1) & 300 cm2 (MC2), FOV 4° X 4°
  • A4 - Hard X-Ray / Low Energy Gamma Ray Experiment :
    seven inorganic phoswich scintillator detectors
    • Low Energy Detectors 15-200 keV, eff. area 2 detectors 100 cm2 each, FOV 1.7° x 20°
    • Medium Energy Detectors 80 keV - 2 MeV, eff. area 4 detectors 45 cm2 each, FOV 17°
    • High Energy Detector 120 keV - 10 MeV, eff. area 1 detector 100 cm2, FOV 37°
* Science Highlights:
  • Complete flux-limited High Galactic Latitude Survey (Piccinotti et al. 1982).
  • Measurement of X-ray background from 3-50 keV (Marshall et al. 1980, ApJ, 235, 4.)
  • Comprehensive catalog of X-ray sources (one for each experiment).
  • Several hundred optical companions and source classifications based on X-ray source positions.
  • Monitored variability of a variety of objects from AGNs to X-ray binaries.
  • Studied aperiodic variability in Cyg X-1 on timescales on a few milliseconds
  • Discovered the first eclipse seen in a low-mass X-ray binary.
* Archive : Catalogs, Spectra, Lightcurves, Maps and Raw data.
Not all are available for all experiments.

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