The Very Large Telescope (VLT) is operated by the European Southern Observatory (ESO) on Cerro Paranal in the Atacama Desert of northern Chile. The VLT consists of four individual telescopes, each with a primary mirror 8.2 m across, which are generally used separately but can be used together to achieve very high angular resolution. These four separate Unit Telescopes (UTs) are known as Antu, Kueyen, Melipal, and Yepun, which are all words for astronomical objects in the Mapuche language. The telescopes form an array which is complemented by four movable Auxiliary Telescopes (ATs) of 1.8 m aperture.
In a major upgrade until end of 2016, Yepun or UT4 was transformed into an adaptive telescope providing turbulence corrected images at all foci. An essential part of the new Adaptive Optics Facility (AOF) is the Four Laser Guide Star Facility (4LGSF) with four TOPTICA SodiumStar 20/2 laser systems. AOF and 4LGSF represent a paradigm shift in laser guide star adaptive optics. Due to the advanced laser technology developed in a collaboration between ESO, TOPTICA and MPB Communications, the preparation time of an observing run and the amount of preventative maintenance needed are significantly reduced. The availability of four lasers providing optimized return flux allows for advanced modes of adaptive optics, in particular ground-layer and laser tomography adaptive optics. Together with the other components of the AOF, these are all cutting-edge technologies paving the way for the era of extremely large telescopes.
Credit: ESO/G. Hüdepohl
