{"paper":{"title":"The metrology system of the VLTI instrument GRAVITY","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.IM","authors_text":"Antonio Amorim, Christian Rau, Christian Straubmeier, David Huber, Eckhard Sturm, Ekkehard Wieprecht, Erich Wiezorrek, Frank Eisenhauer, Frank Haussmann, Guy Perrin, Idel Waisberg, Johannes Weber, Karine Perraut, Magdalena Lippa, Marcus Haug, Markus Plattner, Nicolas Blind, Oliver Hans, Oliver Pfuhl, Reinhard Genzel, Senol Yazici, Stefan Gillessen, Stefan Kellner, Thomas Ott, Tobias Kratschmann, Wolfgang Brandner, Yipting Kok","submitted_at":"2016-08-17T08:10:23Z","abstract_excerpt":"The VLTI instrument GRAVITY combines the beams from four telescopes and provides phase-referenced imaging as well as precision-astrometry of order 10 microarcseconds by observing two celestial objects in dual-field mode. Their angular separation can be determined from their differential OPD (dOPD) when the internal dOPDs in the interferometer are known. Here, we present the general overview of the novel metrology system which performs these measurements. The metrology consists of a three-beam laser system and a homodyne detection scheme for three-beam interference using phase-shifting interfer"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1608.04888","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}