Abstract
We present a simple analytic model of the upper atmosphere which gives the composition, density, and temperature of the neutral atmosphere, as a function of altitude, for a wide range of conditions at the reference altitude of 120 km. The model density profiles are all in good agreement with densities deduced from observations of satellite drag. They therefore demonstrate, quantitatively, that satellite drag data alone cannot determine atmospheric composition and temperature at the reference altitude. In addition, it appears that the uncertainty in the concentration of atomic oxygen in the upper atmosphere is such as to render the exospheric temperatures deduced from satellite drag measurements uncertain by about 25 per cent.
