title: Measuring coalignment of retroreflectors with large lateral incoming-outgoing beam offset.
abstract: A method based on phase-shifting Fizeau interferometry is presented with which retroreflectors with large incoming-outgoing beam separations can be tested. The method relies on a flat Reference Bar that is used to align two auxiliary mirrors parallel to each other to extend the aperture of the interferometer. The method is applied to measure the beam coalignment of a prototype Triple Mirror Assembly of the GRACE Follow-On Laser Ranging Interferometer, a future satellite-to-satellite tracking device for Earth gravimetry. The Triple Mirror Assembly features a lateral beam offset of incoming and outgoing beam of 600 mm, whereas the acceptance angle for the incoming beam is only about ±2 mrad. With the developed method, the beam coalignment of the prototype Triple Mirror Assembly was measured to be 9 μrad with a repeatability of below 1 μrad.
authors.affiliation: Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Institute for Gravitational Physics, Leibniz Universität Hannover, Callinstr. 38, 30167 Hanover, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schütze
authors.affiliation: Commonwealth Scientific and Industrial Research Organisation, Bradfield Road, Lindfield, NSW 2070, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Farrant
authors.affiliation: Centre for Gravitational Physics, Australian National University, Acton, ACT 0200, Australia.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Shaddock
authors.affiliation: Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Institute for Gravitational Physics, Leibniz Universität Hannover, Callinstr. 38, 30167 Hanover, Germany.
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Sheard
authors.affiliation: Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Institute for Gravitational Physics, Leibniz Universität Hannover, Callinstr. 38, 30167 Hanover, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Heinzel
authors.affiliation: Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Institute for Gravitational Physics, Leibniz Universität Hannover, Callinstr. 38, 30167 Hanover, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Danzmann