On-orbit coarse alignment of three mirror anastigmat telescopes utilizing blind scanning and stochastic processes

Abstract

Optical alignment of an astronomical three-mirror anastigmat (TMA) telescope is a challenging endeavor where misalignments may degrade image quality beyond what is possible to correct using simple wavefront measurement techniques. Traditionally, the primary and secondary mirrors of large-scale telescopes are aligned with human feedback as the telescope takes initial images. In these studies, we describe a series of coarse alignment strategies that can be used to align a TMA telescope system autonomously using only information extracted from stars within the field of view. Utilizing a commercial wide field-of-view detector will provide us with a sufficient data set of both on- and off-axis field points to drive alignment. The proposed method is tested against two telescope models, monolithic off- and on-axis TMA telescopes. The results from these simulations demonstrate the ability for a coarse alignment procedure consisting of blind scanning and stochastic processes to improve a TMA from millimeter level misalignment to near diffraction-limited performance via on-board autonomous control.