# Modelling the High Altitude Environment

## Simple Exponential Atmosphere Model:

If you assume that the atmosphere consists of an ideal gas (a reasonable assumption) at constant temperature (not so reasonable), then you come up with the following model of pressure and density vs. altitude:
 Temperature: T = T0, independent of h. Pressure: P = P0 e-h/a Density: r = r0 e-h/a

## 1976 Standard Atmosphere Model:

For altitudes between 32 and 47 km, NASA, NOAA, and USAF use this empirical model:

## Exponential Model 1976 Empirical Model Air Temperature: 288 K = 15 C 251 K = -22 C Air Pressure: P = 876 N/m2 P = 277 N/m2 Air Density: r = 0.0106 kg/m3 r = 0.0039 kg/m3

So, which model did the GLAST Balloon Flight designers use to design their hardware and plan its course? And what conditions did the GLAST Balloon actually encounter at this height? Check the GLAST Flight Parameters page to see what the planners expected, or the GLAST Balloon Flight environmental data page to find out what the balloon actually measured...