Testing P-REx on VLTI data

Abstract

In VIS/IR interferometry the presence of the turbulent atmosphere induces piston drifts, resulting in the optical path difference (OPD) between each telescope to fluctuate. Typically, this is compensated for by employing a fringe tracker. However, the fundamental need for a fringe tracker effectively limits the sensitivity and sky coverage. Previously, a novel method, the Piston Reconstruction Experiment (P-REx), showed how AO data can be used to estimate the piston drift over individual telescopes in order to stabilise the fringes over short timescales and extend the integration time of the fringe tracker. The principle idea behind this method is that the piston drift is simply the product of the wind velocity and the tip and tilt of the atmosphere. In this paper, new developments in the method for estimating the wind velocity will be presented, as well as comparisons between the P-REx OPD estimates obtained from the VLTI’s CIAO WFS data and GRAVITY fringe tracking data.