Space shuttle data and atmospheric models

Atmospheric density data obtained during the reentry of 22 Shuttle flights have been analyzed and compared with models. It was found that the density values from two flights that reentered through high latitudes were quite different from the values obtained from low and mid latitude flights. Data from a December high latitude flight agreed with models, although as low as 60% of the U.S. Standard Atmosphere, but the data from an October flight were as much as 25% below the October models, although 57% of the U.S. Standard. The difference was possibly due to the effects of particle precipitation. Data from the mid and low latitude flights, in general, agreed well with the models, with a mean deviation of −2.3% at 50km and −11% at 85km. The maximum variability at these altitudes was 8% and 22%, respectively. Most flights showed evidence of gravity waves above 70km, with largest amplitudes in summer, and little activity in the winter or at high latitudes. Data from three flights that reentered at a constant latitude of 27°N are close to the models near 50km, but are generally lower at higher altitudes and exhibit major variability above 70km, probably due to storm and convective activity. The results from three high inclination flights that reentered over the southern tropics agree with the models at 50km altitude, but at higher altitudes all the data are below the models. The conclusion is that the models for latitudes between 20°N and 20°S need to be revised.