Early model of dimpling, showing the typical features of grating lobes. The model is calculated at 217 GHz, and has the theoretical Planck geometry, with the addition of 10 μm amplitude dimples on both primary and secondary reflectors. The contour levels are at intervals of 10 dB from the peak amplitude (66.7 dBi); the outermost lobes show contours at −13 dBi. The main lobe is in the center of the grid. The horizontal and vertical axes are in degrees, in the cross-scan and co-scan directions respectively.