A team from the Isaac Newton Group of Telescopes in collaboration with scientists from Durham University in the United Kingdom and from the University of Leiden and the ASTRON institute in The Netherlands have developed and commissioned at the William Herschel Telescope on the island of La Palma the first ground-layer adaptive optics system in the world that can be used for general astronomical observations. Its purpose is to produce sharper images so that astronomers can study celestial objects in much greater detail than what is usually feasible from the ground.
The ground-layer adaptive optics system, or GLAS, works with a high-tech pulsed laser. The laser beam is projected from a small telescope mounted behind the secondary mirror of the William Herschel Telescope, producing an artificial star in the sky at an altitude of 15 kilometres. The light coming from the artificial star is detected by a sensor that measures the atmospheric distortions. This information is used at a rate of several hundred times per second to shape a rapidly adjustable deformable mirror to take out the adverse effects of atmospheric turbulence. The somewhat low altitude of the artificial star implies that air turbulence nearer the ground is preferentially illuminated and corrected, and therefore it is usually referred to as ground-layer adaptive optics.
The importance of such a laser adaptive optics system goes beyond the immediate scientific interests at the William Herschel Telescope. Scientists are currently developing future extremely large telescopes that will have mirror diameters of thirty or even forty meters. These future huge telescopes will have to rely on adaptive optics with lasers, and correction of ground-layer turbulence will be of crucial importance.
This project was made possible through a grant from the Division for Physical Sciences of the Netherlands Organisation for Scientific Research, with assistance from the OPTICON network funded by the European Union.
The William Herschel Telescope is part of the Isaac Newton Group of Telescopes (ING). The ING is owned and operated jointly by the Science and Technology Facilities Council (STFC) of the United Kingdom, the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) of the Netherlands and the Instituto de Astrof¨ªsica de Canarias (IAC) of Spain. The telescope is located in the Spanish Observatorio del Roque de los Muchachos on La Palma, Canary Islands, Spain. The international observatory is operated by the Instituto de Astrof¨ªsica de Canarias (IAC).