Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


First Ground-Layer Adaptive-Optics System for General Astronomical Observations

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 Astrofísica 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 Astrofísica de Canarias (IAC).


Even the biggest and best astronomical telescopes on the highest mountains and under pristine clear skies are hampered by the Earth’s atmosphere in their endeavour to look sharply into the cosmos. Subtle variations of air temperature cause the starlight to become distorted before it reaches the telescope. There, the rapidly changing distortions result in images from far away stars and galaxies becoming blurred, which poses a severe restriction on the capability of telescopes on the ground.

To counteract the disturbing effect of the earth’s atmosphere, scientists and engineers have developed techniques that allow them to measure and correct for the atmospheric distortions in an attempt to try to recover a perfectly sharp picture. A small mirror whose shape can be rapidly adjusted corrects for the atmospheric distortions. This technique is referred to as adaptive optics and is being used at a number of telescopes around the world, including the 4.2-m William Herschel Telescope on the island of La Palma, in the Canary Islands.

Although adaptive optics has been in operation on a regular basis for some years, the real benefits for astronomical research can only be unleashed when the technique is used in conjunction with a laser beam that generates a point source of light in the sky. This point, or artificial star, can then be used to measure the distortions caused by the Earth’s atmosphere. Without such a laser only a very small fraction of the sky can be studied, while with a laser nearly the full sky is available for scientific studies. This provides a remarkable advantage for astronomers.

It is not customary to see artificial lights at an astronomical observatory at night. Lights in general badly affect professional telescopes. The laser light used here, however, does not affect the observations because it is very well focused and works at only one very specific colour. Moreover, a system has been implemented that coordinates where all telescopes are pointing and prevents the laser from adversely affecting other telescopes.

The laser beam is only visible by the unaided eye from close to the telescope building. Time exposures clearly show the green laser beam coming from the telescope. The artificial star that the laser produces is much too faint to be seen by the unaided eye, but is of course bright enough to be seen with the telescope.

Javier Méndez | alfa
Further information:

More articles from Physics and Astronomy:

nachricht Mars 2020 mission to use smart methods to seek signs of past life
17.08.2017 | Goldschmidt Conference

nachricht Gold shines through properties of nano biosensors
17.08.2017 | American Institute of Physics

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>



Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Latest News

Gold shines through properties of nano biosensors

17.08.2017 | Physics and Astronomy

Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter

17.08.2017 | Earth Sciences

Mars 2020 mission to use smart methods to seek signs of past life

17.08.2017 | Physics and Astronomy

More VideoLinks >>>