The dual-channel COSIE design uses a rotating flip mechanism to select between the wide-field imager COSIE-C channel (left) and the slitless spectrograph COSIE-S channel (right). Solar EUV enters from the upper left, as indicated by the blue arrows, with visible light blocked by a thin Al entrance filters. Light then reflects from the rotatable flip mechanism selector onto a multilayer-coated focusing optic that is alternately used by both channels.