Abstract
A SEMI-ANNUAL variation in upper-atmosphere density, with maxima in April and October, and minima in January and July, was discovered in 1960 and has been generally accepted as a feature of the upper atmosphere at heights of 250–600 km. In a recent article, Anderson1 suggested that the variation is a disguised effect of latitude. Anderson's hypothesis can be tested by analysing the orbit of a satellite of a near-circular polar orbit which samples all latitudes in a nearly equal degree. If the semi-annual variation is recognizable in the orbit of such a satellite, it cannot be due to changes in latitude.
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References
Anderson, A. D., Nature, 209, 656 (1966).
Merson, R. H., and Neville, E. R., Orbital Parameters of Samos 2, R.A.E. Tech. Rep., 66042 (1966).
King-Hele, D. G., Theory of Satellite Orbits in an Atmosphere, chapt. 5 (Butterworths, London, 1964).
Cook, G. E., and King-Hele, D. G., Phil. Trans., 259, 33 (1965).
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KING-HELE, D. Semi-annual Variation in Upper-atmosphere Density. Nature 210, 1032 (1966). https://doi.org/10.1038/2101032a0
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DOI: https://doi.org/10.1038/2101032a0
