Figure 3.

Observed mean radiances at the Pancam from the 10 regions of interest shown in Figure 1. The data points are color coded blue, green, yellow, and red for the four color corner patches and black, dark gray, and light gray for the three gray scale rings (black, gray, and white). Filled circles are sunlit regions. Open circles are the three shadowed regions of the gray scale rings. Error bars give the standard deviation from the mean radiance among the selected pixels. The x axis gives the reflectance factor of the dusty caltarget as returned by the fit to the two‐layer dust reflectance model. Input w_M was 0.804, and τ _cal was found to be 0.52 (see text). Sunlit and shadowed regions are shown with different assumed reflectance factors because of the different angular distribution of incoming light. For sunlit the reflectance factor is (J ₁ /J) · R* _Direct  + (J ₂ /J) · R* _Diffuse. For shadowed regions it is R* _Diffuse. Compare this figure with Figure 2.