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Laser sources for ESO’s ELT and GRAVITY+ now completed

30 septembre 2024

Today, at a ceremony near Munich, staff from ESO and German company TOPTICA celebrated the completion of the last laser source of ESO’s Extremely Large Telescope (ELT). Lasers for the GRAVITY+ upgrade to ESO’s Very Large Telescope Interferometer (VLTI) have also been completed.

The ELT will be equipped with six powerful lasers [1] that will excite sodium atoms in Earth's upper atmosphere, creating artificial stars. These ‘stars’ are used to measure the blurring caused by the atmosphere so that the ELT’s adaptive mirrors can correct for it. By employing sophisticated "adaptive-optics" systems, the telescope and its instruments can obtain sharper images than any other ground-based telescope.

TOPTICA, in partnership with the Canadian company MPB Communications Inc. (MPBC), has just completed production of a series of 9 laser sources, which generate the laser light. Six of these will be used on the ELT and three on GRAVITY+, an extensive upgrade being done to ESO’s VLTI and its GRAVITY instrument. All nine laser sources have now been completed and delivered to ESO. The recent laser production continues a successful programme of work, which started in 2009, with the goal of developing and industrialising a laser technology suitable for sodium laser guide stars at astronomical telescopes.

ESO will be responsible for integrating the laser sources with the remaining components that make up the laser guide star units. Each unit includes, in addition to the light source, a projection subunit, which expands the laser beam and directs it into the sky, and a heat exchanger, to stabilise the temperature of the laser source. Dutch organisation TNO is contracted to provide the projection subunits, while Italian company Tecoelettra has delivered the heat-exchanger units.

Similarly to the lasers on ESO’s Very Large Telescope, each of the new lasers will deliver 22 watts of yellow-orange laser light — about 4000 times the maximum allowed for a commercial laser pointer — in a beam with a diameter of 30 centimetres. Thanks to these lasers, the ELT will be able to deliver razor-sharp images all over the sky.

Once it sees first light later this decade, ESO’s ELT will allow us to peer deeper and further into the Universe than ever before. The telescope is currently under construction in Chile’s Atacama Desert.

Notes

[1] The ELT can accommodate a total of eight laser guide stars. It will be equipped with six at the time of first light, with the possibility to increase to eight lasers in the future.