ESO VLTI delay lines

The ESO Very Large Telescope Interferometer (VLTI) Delay Lines in the tunnel at Cerro Paranal, Chile. The Delay Lines were designed and built in the Netherlands by Fokker Space (now Dutch Space) and TNO. The Delay Lines equalise the optical path length of the UT and AT telescopes in interferometer mode down to a few nanometers. Currently 6 Delay Lines have been installed.