The atmosphere does not have a definite thickness since it gradually thins with altitude, with a consequent decrease in attenuation. However, if we use a simplified "orange peel" model and assume that the atmosphere can be approximated by a uniform layer of fixed thickness, we can estimate the background noise temperature seen through the atmosphere. Thus, let the thickness of the atmosphere be 4000 m, and find the maximum distance to the edge of the atmosphere along the horizon, as shown in the figure below (the radius of Earth is 6400 km). Now assume an average atmospheric attenuation of 0.005 dB/km, with a background noise temperature beyond the atmosphere of 4 K, and find the noise temperature seen on Earth by treating the cascade of the background noise with the attenuation of the atmosphere. Do this for an ideal antenna pointing toward the zenith, and toward the horizon
