==== Case D2: Rayleigh scattering layer above Lambertian surface ====

This case includes the same setup as case D1 but with smaller optical thickness and a Lambertian surface below the Rayleigh scattering layer. 

//Setup://

  * optical thickness of layer: 0.1
  * surface albdeo: 0.3
  * Rayleigh depolarization factor: 0.03
  * no molecular absorption
  * Earth radius: 6371 km
  * Thickness of layer: 120 km

  * Sun-observer geometries as defined in general settings:
      * //viewing zenith angles// (deg): [0, 9, 18, 26, 34, 41, 48, 54, 60, 65, 70, 74, 78, 81, 84, 86, 88, 89, 90] (up-looking at bottom of atmosphere, down-looking at top of atmosphere]
      * //viewing azimuth angles// (deg): 0-180, 10° increment 
      * //solar zenith angles// (deg): [30, 60, 80, 87, 90, 93, 96, 99]
      * //solar azimuth angle// (deg): 0
      * //sensor altitude// (km): 0, 120