Fiber-Connected Wavefront-Sensing System for Large Segmented Space Telescopes

A metrology system capable of cofocusing and cophasing is essential to ensure the performance of large segmented space telescopes, similar to that of monolithic telescopes, as well as to image the faintest galaxies. A fiber-linked-wavefront-sensing system can map pupils from 10 m to 0.1 mm, avoiding the volume, weight, power, and dispersion limitations of free-space light paths. In this study, the coupling efficiency was investigated while cofocusing on the telescope-mirror segments. Fiber-linked-channel-spectrum interferometry was proposed to accomplish fine phasing, and a photonic lantern was proposed to achieve coarse phasing. The cofocus and cophasing accuracies exceeded 12 mu m and 15 nm, respectively, in the 170 mu m range. This study aimed to resolve the problems of restricted optical path spaces and decoherence encountered during the cofocusing and cophasing processes of large-space telescopes. It also expands the application range of astronomical photonics in large-space telescopes. The size and mass of the optical alignment system directly limit the amount of fuel and coolant used for the operation of large- or sparse-aperture telescopes in space. The use of fiber-optic interconnection systems can significantly reduce the mass and inertia of the telescope, which is crucial for large-aperture-space-telescope construction.