2014/04/30 by S. Lacour, F. Eisenhauer, S. Gillessen +12 · 3 citations
Computer Science · Engineering · Physics and Astronomy · #Adaptive optics #Adaptive optics and wavefront sensing #Advanced Measurement and Metrology Techniques #Astrometry #Astronomical interferometer #Astrophysics #Baseline (sea) #Interferometry #Metrology #Optical measurement and interference techniques #Optical path #Optical path length #Optics #Physics #Scalar (mathematics) #Stars #Telescope #Very-long-baseline interferometry #astro-ph.IM
paper · pdf · doi:10.1051/0004-6361/201423940
published as A&A 567, A75 (2014) · 14 pages. Accepted by A&A
arxiv created 2014/05/24 · openalex publication_date 2014/06/13 · arxiv updated 2014/09/05 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Context. A basic principle of long baseline interferometry is that an optical path difference (OPD) directly translates into an astrometric measurement. In the simplest case, the OPD is equal to the scalar product between the vector that links the two telescopes and the normalized vector pointing toward the star. However, in some circumstances, too simple an interpretation of this scalar product leads to seemingly conflicting results, called here "the baseline paradox". Aims. For micro-arcsecond accuracy astrometry, we have to model the metrology measurement in full. It involves a complex system subject to many optical effects: from pure baseline errors to static, quasi-static, and high-order optical aberrations. The goal of this paper is to present the strategy used by the "General Relativity Analysis via VLT InTerferometrY" instrument (GRAVITY) to minimize the biases introduced by these defects. Methods. It is possible to give an analytical formula for how the baselines and tip-tilt errors affect the astrometric measurement. This formula depends on the limit points of three type of baselines: the wide-angle baseline, the narrow-angle baseline, and the imaging baseline. We also numerically include non-common path, higher order aberrations, whose amplitudes were measured during technical time at the Very Large Telescope Interferometer (VLTI). We end by simulating the influence of high-order, common-path aberrations due to atmospheric residuals calculated from a Monte-Carlo simulation tool for adaptive optics (AO) systems.