Atmosphere Models

US Standard Atmosphere 1976 Model

The US Standard Atmosphere 1976 model is used for the majority of the atmospheric scenarios and represents the Earth's atmosphere from the surface to 1,000 km in geometric altitude. This model can be implemented as linear interpolation of 1D tables at varying fidelity and contains ambient pressure, temperature, and density as a function of either geometric altitude (h) or geopotential height (Z). More information regarding this atmosphere model can be found here.

Marshall Engineering Thermosphere Model (MET)

The Marshall Engineering Thermosphere model is a static diffusion model following the Smithsonian's Jacchia 1970 model with two enhancements from the Jacchia 1971 model. The intention of this atmosphere model is to represent the variability of ambient mass density at orbital altitudes and is the standard atmospheric density model for studies involving orbiting spacecraft.

Inputs to the model are time (year, month, day, hour, and minute), position (altitude and geographic latitude and longitude), the previous day's solar radio flux (F_10.7), the centered solar radio flux averaged over six solar rotations (F_10.7), and the a_p index from 6 to 7 hours before the time in question. From these inputs, the model computes total mass density, temperature, pressure, individual species number densities, mean molecular weight, scale-height, specific heats, and the local gravitational acceleration. More information regarding this model can be found here.

Below is a table showing how different orbital scenarios were modeled using varying levels of solar activity. These levels consist of minimal, mean, and maximal solar activity and allow for deeper assessments of environmental impacts to a space vehicle.