SMART: Special-shaped Micro-lens Aimer for Real-time Targeting of multi-object telescopes

Abstract

In the process of acquiring astronomical spectral data, the alignment accuracy between the fiber core in the focal plane and the image of the target star is crucial for multi-target telescopes. This work presents a Special-shaped Micro-lens Aimer for Real-time Targeting (SMART), which combines a special-shaped microlens and a fiber bundle to carry out online alignments and improve the injection efficiency of the fiber. The special-shaped microlens consists of a central plate and six side microlenses. The central plate transfers the signal to the science fiber without focal ratio degradation. The side microlenses focus the leakage light to the feedback fibers and return a misalignment signal. The experiment in the laboratory indicates that the SMART-T system can visually demonstrate the recognition of offsets. The SMART-P system is able to realize the alignment for a variety of seeing cases. Under the condition that the diameter of turbulent star image is 0.2 mm, the corrected injection efficiency is improved to 99.7% of the best injection efficiency of the science fiber. The re-centering accuracy is 0.01 mm.