Kinematics, composition and thermodynamics of the mesopause, turbopause, region of the atmosphere (between 80 and 120 km) related to the Aeroassisted Orbit Transfer Vehicle (AOTV) operations

摘要

The mesopause-turbopause region (80 to 120 km) of the atmosphere which is frequently used as a boundary between the thermosphere and mesosphere for models of the atmosphere is discussed. The initialization of models is important since uncertainties may lead to significant changes in the computations of total density at greater altitudes. In this transition region, the experimental data base for the total gas density and the constituents of smaller abundance is very limited. The turbopause height (h sub t) may vary from 90 to 120 km and no pronounced dependence of (h sub t) on season, local time, or solar activity is determined. The importance of atmospheric turbulence is discussed and its important role in the mesosphere and lower atmosphere by influencing the thermal balance of the upper atmosphere, as well as the distribution of different atmospheric constituents, is presented. The number of measurements of turbulence at these altitudes is small. Data from radio meteors, noble gas ratio analysis, and luminescent cloud analysis reveal no definite conclusion or systematic variation of the turbulence region. The heat input by gravity waves is a dominant term in the energy balance equation. Also gravity waves, either directly or through a mechanism of turbulence generation, enhance the mixing ability of the atmosphere. Internal gravity waves produce variations in the density as well as concentration of atomic oxygen. The uncertainty in the atmospheric density variation leads to control system design problems for the AOTV relative to the control authority required to deal with the unpredictable variation in density.