Dictionary  High' En'ergy Astrophys'ical Observ'atoryone of a series of three U.S. satellites launched (1977–79) into orbit around the earth and equipped with instruments for studying high-energy phenomena, as x-rays, gamma rays, and cosmic rays. Abbr.: HEAO Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.
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