High-efficiency echelle gratings for MIGHTI, the spatial heterodyne interferometers for the ICON mission

Development of a new generation of low-groove density-blazed echelle gratings optimized for MIGHTI, a space-borne spatial heterodyne interferometer operating in the visible and near infrared is described. Special demands are placed on the wavefront accuracy, groove profile, and efficiency of these gratings. These demands required a new ruling for this application, with significant improvements over existing gratings. Properties of a new generation of highly efficient, plane gratings with $64\text{grooves}/\mathrm{mm}$ blazed at 8.2° are reported.