Progress of the CHARA/SPICA project

TL;DR

The paper discusses the development and initial results of the CHARA/SPICA project, a high-precision stellar observation instrument combining advanced fringe tracking and fiber optics at the CHARA Array.

Contribution

It introduces the design, features, and first laboratory and on-sky results of the SPICA-VIS beam combiner and fringe tracker, advancing stellar imaging capabilities.

Findings

Successful laboratory testing of SPICA-FT fringe tracker

First on-sky fringe stabilization results achieved

Development of a new fringe-tracker simulator

Abstract

CHARA/SPICA (Stellar Parameters and Images with a Cophased Array) is currently being developed at Observatoire de la C\^ote d'Azur. It will be installed at the visible focus of the CHARA Array by the end of 2021. It has been designed to perform a large survey of fundamental stellar parameters with, in the possible cases, a detailed imaging of the surface or environment of stars. To reach the required precision and sensitivity, CHARA/SPICA combines a low spectral resolution mode R = 140 in the visible and single-mode fibers fed by the AO stages of CHARA. This setup generates additional needs before the interferometric combination: the compensation of atmospheric refraction and longitudinal dispersion, and the fringe stabilization. In this paper, we present the main features of the 6-telescopes fibered visible beam combiner (SPICA-VIS) together with the first laboratory and on-sky results of the fringe tracker (SPICA-FT). We describe also the new fringe-tracker simulator developed in parallel to SPICA-FT.