Upper-atmosphere density, determined from the orbits of Cosmos rockets

Abstract

Observational values of air density at heights of 150–200 km at times of low solar activity are still sparse. In this paper the orbits of thirty-two Cosmos rockets and two other satellites are examined, to obtain new values of air density from the orbital changes. An improved method is used for satellites very near the ends of their lives. The results strengthen the previous picture of the day-to-night variation in air density at heights of 200–300 km, and indicate a substantial day-to-night variation of density down to 170 km at times of low solar activity. The results at heights between 160 and 200 km suggest that recent theoretical models do not allow a large enough day-to-night variation in density. The analysis also shows, incidentally, that the mass/area ratios of the Cosmos rockets with inclinations of 65° differ appreciably from the values for those with inclinations of 49°.