P-REx: The Piston Reconstruction Experiment for infrared interferometry

Abstract

For sensitive infrared interferometry, it is crucial to control the differential piston evolution between the used telescopes. This is classically done by the use of a fringe tracker. In this work, we develop a new method to reconstruct the temporal piston variation from the atmosphere, by using real-time data from adaptive optics wavefront sensing: the Piston Reconstruction Experiment (P-REx). In order to understand the principle performance of the system in a realistic multilayer atmosphere it is first extensively tested in simulations. The gained insights are then used to apply P-REx to real data, in order to demonstrate the benefit of using P-REx as an auxiliary system in a real interferometer. All tests show positive results, which encourages further research and eventually a real implementation. Especially the tests on on-sky data showed that the atmosphere is, under decent observing conditions, sufficiently well structured and stable, in order to apply P-REx. It was possible to conveniently reconstruct the piston evolution in two-thirds of the datasets from good observing conditions (r 0 ∼ 30 cm). The main conclusion is that applying the piston reconstruction in a real system would reduce the piston variation from around 10 µm down to 1 to 2 µm over timescales of up to two seconds. This suggests an application for mid-infrared interferometry, for example for MATISSE at the VLTI or the LBTI. P-REx therefore provides the possibility to improve interferometric measurements without the need for more complex AO systems than already in regular use at 8m-class telescopes.

Searching for Protoplanets around MWC 758 and MWC 480 in Br-γ Using Kernel Phase and SCExAO/CHARIS

“…In the future, this limit may be improved, reaching as low as K = 22 in the case of the future VLIT/GRAVITY+ instrument (Gravity+ Collaboration 2022). For long-baseline interferometry, in general, improving sensitivity is a matter of boosting adaptive optics (AO) performance using better hardware or improved understanding of the effects of the atmosphere (e.g., P-REX; Widmann et al 2018;Perera et al 2022).…”

Image-plane fringe tracker for adaptive-optics assisted long baseline interferometry

“…9 In this paper, we propose that the adaptive optics system and fringe tracker should be seen as a more integrated system that provides a high spatial cohrerence beam to the science combiner, also enabling low spectral resolution science. Note that we are not considering piston reconstruction in this paper, 10 which is an separate but also highly valuable reason to consider fringe tracking and adaptive optics as an integrated system.…”