Thermospheric mass density: A review

The mass density of Earth\textquoterights thermosphere (\~90\textendash600\ km altitude) is a critical parameter for low Earth orbit prediction because of the atmospheric drag on satellites in this region. In this review, we first survey techniques for measuring thermospheric density, empirical models that provide a synthesis of historical data, and physical models that simulate the environment by solving fluid equations. We then review the climate and weather features that are observed in thermospheric density (including its response to solar forcing) and summarize recent studies of these features. The review is focused on results published between 2000 and 2014, which coincides with a period of extensive accelerometer measurements of density and accompanying research; some historical context is also provided.