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The polarization twist imposed on 106.1 Mc/s radio waves by the ionosphere has been investigated by using the moon as a passive reflector, the purpose being to determine the total electron column density even at altitudes above the known ionosphere. Because the antenna is capable of being continuously directed at the moon for 12 consecutive hours, observations are possible from the pre-dawn ionization minimum to the noon-time maximum. A true-height profile computed from vertical-incidence ionosonde data of September 16, 1957, suggests that the total electron content throughout the entire ionosphere is not a constant factor of the integrated electron content computed up to the level of maximum ionization density.
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Hill et al. (1960) studied this question.
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