This  directory contains soubroutines for Atmosphere structure.
The earth is assumed to be a complete sphere.
The atmosphere is an approximation to U.S standard
one: this approximation is good at height <
40 km. At around 100 km,  the atmosperic depth
is computed as 0.1 g/cm2 while better approximation
gives 0.2g/cm2.
 At altitude > 100km, the approximation becomes worse.
  If we need this better approximation
we may use

   stdatmos1.d, stdatmos2.d 
and cstdatmos0.f. cstdatmos0.f is not yet
completed.

