where a is the semimajor axis, and e is the eccentricity, i.e. e = 0.093377; and 0 is the true anomaly given by: where Ls is the aerocentric longitude and 248° is the aerocentric longitude of Mars' perihelion. The Sun-Mars mean distance in AU units is 1.5236915, therefore, the mean beam insolation at the top of Mars' atmosphere is: 1371/1.52369152= 590 W/m2. The instantaneous beam insolation is given by Equations (11-13): The following figures of solar insolation were calculated using the Table I data and the mean insolation of 590 W/m2. Insolation values for any desired seasonal data Ls are easily obtained using Equation (14). The global insolation Gh on a horizontal Martian surface is obtained by: The beam insolation Gbh on a horizontal surface is obtained using Equation (9) for Gb = 590 W/m2, and is shown in Fig. 11 as a function of the optical depth with the zenith angle as a parameter. The figure shows a sharp exponential decrease in insolation with increasing r.
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