Fringe tracking and spatial filtering: phase jumps and dropouts

TL;DR

This paper investigates phase jumps and dropouts in fringe tracking for interferometers with large apertures and partial adaptive optics, highlighting the impact of speckle noise on phase measurements and algorithm design.

Contribution

It presents simulations demonstrating how speckle noise causes phase branch points and jumps, informing the development of more robust fringe tracking algorithms.

Findings

Speckle noise induces phase branch points and jumps.

Large apertures with partial AO correction exacerbate phase measurement issues.

Simulations help understand implications for fringe tracking algorithm design.

Abstract

Fringe tracking in interferometers is typically analyzed with the implicit assumption that there is a single phase associated with each telescope in the array. If the telescopes have apertures significantly larger than r0 and only partial adaptive optics correction, then the phase measured by a fringe sensor may differ significantly from the "piston" component of the aperture phase. In some cases, speckle noise will cause "branch points" in the measured phase as a function of time, causing large and sudden jumps in the phase. We present simulations showing these effects in order to understand their implications for the design of fringe tracking algorithms.