Phasing a deployable sparse telescope

TL;DR

This paper presents a method for fine-tuning a deployable sparse space telescope by selecting unique segment shapes, correlating focal images, interferometrically measuring optical path differences, and optimizing the overall alignment.

Contribution

It introduces a novel alignment procedure for sparse space telescopes that does not require direct wavefront measurement, improving deployment accuracy.

Findings

Successful segment tilt correction via template correlation

Optical path differences determined through pairwise interference

Enhanced focal image quality after optimization

Abstract

After launching and deploying a sparse space telescope, fine tuning is required to correct for inaccurate initial placement of its elements. We selected unique shapes and locations of these telescope aperture segments, to be able to distinguish between their diffraction patterns, while at the same time having a proper spatial frequency coverage. Then we improved the combined wave front, without measuring it directly: First we correlated each segment's focal image with its distinctive template, to correct its tilt. Next we interfered them with the other segments, pair by pair, using their limited coherence, to locate their mutual optical path differences. Finally, we optimized the combined focal image for fine alignment.