Configuration of the 9 subapertures in FIRST. Left: image of FIRST’s MEMS conjugated with the Subaru Telescope pupil. The sub-apertures are numbered after the segment index. Right: image of the pupil plane after the micro-lens array, where each lens is conjugated to a MEMS segment: the camera detector is conjugated to both the MEMs plane and the microlens array. In green are highlighted the 9 segments used in FIRST.