O Thou Who by a Star Didst Guide

ESO has signed a new agreement with the German photonics company Toptica for the production of lasers to be used in ESO’s Extremely Large Telescope ELT adaptive optics system. Toptica, in partnership with the Canadian company MPB Communications Inc., will build at least four laser sources for the ELT, helping the telescope to achieve unprecedented spatial resolution for an optical / infrared ground-based telescope. The ELT is scheduled to see first light in 2024.

This artist’s rendering shows the ELT in operation on Cerro Armazones in northern Chile. The telescope is shown using eight lasers to create artificial stars high in the atmosphere. (Source: ESO, L. Calçada)

The laser system for the adaptive optics system on the ELT will be based on the Four Laser Guide Star Facility “4LGSF” on ESO’s Very Large Telescope, VLT. The Adaptive Optics Facility, which uses the 4LGSF, has already shown spectacular improvement in image sharpness on the VLT. The Toptica / MPBC Guidestar Alliance was the main contractor for the laser system on the VLT.

Adaptive optics compensate for the blurring effect of the Earth’s atmosphere, enabling astronomers to obtain much sharper images. Lasers are used to create multiple artificial guide stars high in the Earth’s atmosphere. These points of light are used as reference light sources to allow the adaptive optics system to compensate for turbulence in the Earth’s atmosphere. Unlike natural guide stars, laser guide stars can be positioned anywhere to allow the full power of adaptive optics to be used over almost the entire sky.

The ELT is designed to potentially have up to eight laser guide star systems in future. Anticipated observations enabled by the adaptive optics system include everything from studying black holes to investigating some of the youngest galaxies in the distant Universe.

Toptica has pioneered the development of diode-laser based fiber-amplified guide star laser systems at 589 nm (sodium resonance) for astronomical applications over the last ten years. Recently, together with their partner MPB Communications, Toptica was presented with a prestigious Berthold Leibinger Innovation Award and the team received the Forman OSA Award earlier this year. Over the past years, further large telescope sites have adopted the guide star laser technology under the brand name “SodiumStar 20/2” into their existing astronomy facilities. Other areas of interest for SodiumStar lasers are in satellite tracking and lidar. This well-established laser technology of fixed single frequency or tunable single frequency with output powers of tens of Watts can also be transferred to other wavelengths in the range from 520 nm to 640 nm. (Sources: ESO / Toptica)

Reference: M. Enderlein & W. G. Kaender: Sodium Guide Star (R)Evolution, Optik & Photonik, online 16. Dezember 2016; DOI: 10.1002/opph.201600038

Link: Extremely Large Telescope, European Southern Observatory • SodiumStar high-power guide star laser, TOPTICA Projects GmbH, Graefelfing, Germany

Further reading: Sodium Guide Star (R)Evolution, PhotonicsViews, 21. Dezember 2016Guide Star Alliance receives OSA Engineering Award, PhotonicsViews, 4. September 2017

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