THE SEMI-ANNUAL VARIATION IN UPPER-ATMOSPHERE DENSITY, AS REVEALED BY SAMOS 2.
ROYAL AIRCRAFT ESTABLISHMENT FARNBOROUGH (UNITED KINGDOM)
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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 200-600 km. Recently it has been suggested that the semi-annual variation may be disguised effect of latitude this hypothesis can best be tested by analyxing the orbit of a polar satellite in a near-circular orbit. Samos 2 is such a satellite and its orbit is analysed in this paper. The results show a clear semi-annual variation in air density at a height of 500 km in 1961-2, with the maximum density October exceeding the minimum January and July by a factor of 2. The April maximum is about 20 lower than that in October. Latitude has no influence on the result. Author
- Atmospheric Physics