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Cosmic X-Ray Experiment (A-2)

NSSDC ID: 1977-075A-02
Mission Name: HEAO 1
Principal Investigators: Dr. Elihu A. Boldt, Dr. Gordon P. Garmire


This experiment was designed to measure the diffuse X-ray background in the energy range of 0.15 to 60 keV. Objectives were to measure relative diffusion and absorption of diffuse hard and soft X-rays at high galactic latitudes and correlate these measurements with radio and optical studies; to determine discrete source background contribution; to detect large-scale global anisotropies associated with solar system motion with respect to distant emission sources; to make broadband spectral classifications of diffuse and discrete X-ray sources; and to establish temporal variations of multicomponent spectral sources. Three types of multianode, multilayer counters were used for this experiment. Three high-energy detectors (HED) with xenon-filled counters covered the energy range of 3 to 60 keV with an effective area of 900 sq cm. The minimum detectable flux in a 1E3-s observation was 1E-4/sq cm-s-keV for energy bands 3 to 20 keV and 20 to 60 keV. One medium energy detector (MED) with an argon-filled counter covered the energy range 1.5 to 15 keV. The effective area of this counter was 900 sq cm. The minimum detectable flux was the same as for the HEDs. The two low-energy detectors (LED) were thin-window, propane gas flow counters to cover the energy range of 0.15 to 3 keV. The LED used permanent magnets to prevent incident electrons from reaching the detector window and a sunshade whenever direct sunlight was near the field of view. It had a 600-sq cm effective area. The minimum detectable flux for a 1E3-s observation was 1E-3/sq cm-s-keV for the 0.15- to 0.28-keV band and for the 0.5- to 3.0-keV band. The LEDs were shut down in May 1978 because of depletion of gas in the system. For more details, see R. Rothschild et al., Space Science Instr., v. 4, p. 269, 1979.

Funding Agency

  • NASA-Office of Space Science (United States)


  • Astronomy: X-Ray

Additional Information

Questions or comments about this experiment can be directed to: Dr. Cynthia Y. Cheung.



NameRoleOriginal AffiliationE-mail
Dr. Gordon P. GarmirePrincipal InvestigatorPennsylvania State
Dr. Elihu A. BoldtPrincipal InvestigatorNASA Goddard Space Flight
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