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The main components of the earth's exosphere are neutral oxygen, neutral hydrogen atoms, ionized oxygen, and ionized hydrogen. The position of the base of the exosphere is established at an altitude of 530 km, from an analysis of density data obtained from satellite drag observations. The relative distribution of both neutral oxygen and neutral hydrogen is derived from a theory of the exosphere. The normalization of oxygen is accomplished by means of satellite drag data. The normalization of hydrogen is accomplished by means of the Lyman-α technique of Johnson, Friedman, and Tousey. The distribution of ionized oxygen can be established jointly from the rocket measurements of Berning and from an analysis of radiation belt data obtained from satellites. They give a consistent picture of ionized oxygen becoming the most important constituent of the atmosphere at about 1500 km. The distribution of ionized hydrogen is only imperfectly known.
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S. Fred Singer (1960) studied this question.
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