Abstract: Methods, apparatus and systems are described that relate to in-situ and in-process assembly of segmented optical component with high accuracy. One example method for assembling an optical component with multiple segments includes positioning the multiple segments to an initial state conforming to an alignment or positioning requirement, measuring positions of the multiple segments at the initial state, initiating a fusing process to fuse the multiple segments of the optical element together, measuring the positions of the multiple segments after commencement of the fusing process, and determining whether a change in the positions of the multiple segments has occurred that causes a deviation from the initial state. Upon a determination that the deviation is not within a tolerance value, the method includes adjusting a position of at least one of the multiple segments to maintain the deviation within the tolerance value.