Dark tip-tilt sensing

TL;DR

This paper explores a dark tip-tilt sensing method using a quad-cell with an occulting disk, analyzing its performance through simulations within adaptive optics systems employing natural guide stars.

Contribution

It introduces a novel dark wavefront sensing technique and evaluates its effectiveness via simulations considering residual jitter in adaptive optics.

Findings

Dark tip-tilt sensing can operate with fainter guide stars.

Performance depends on the size of the occulting disk relative to residual jitter.

Simulations show potential for improved tip-tilt measurement in adaptive optics.

Abstract

Dark wavefront sensing in its simplest and more crude form is a quad-cell with a round spot of dark ink acting as occulting disk at the center. This sensor exhibits fainter limiting magnitude than a conventional quad-cell, providing that the size of the occulting disk is slightly smaller than the size of the spot and smaller than the residual jitter movement in closed loop. We present simulations focusing a generic Adaptive Optics system using Natural Guide Stars to provide the tip-tilt signal. We consider a jitter spectrum of the residual correction including amplitudes exceeding the dark disk size.