1976 Standard Atmosphere
As published by NOAA, NASA, and USAF
The standard atmosphere is mathematically modeled in seven layers from sea level to 86 km.
(The KAO experiment had a maximum altitude of 41,000 ft or 12,500 m. Phase two of the experiment, on top of Mauna Kea was at an altitude of 13,100 ft or 4000 m.)
The results of the empirical formulas for Density and Pressure for layer 1 are so similar to those for layer 2 that they are comparable to within 1 percent up to 15km. Therefore, we can use the layer 1 equation for most altitudes of interest.
Layer 1, Troposphere: