VDL ETG Projects, part of VDL Groep, is to build the support structure for the main mirror of the Extremely Large Telescope (ELT) in northern Chile. At a height of over 3 kilometres, the world's largest telescope of ESO (European Southern Observatory) will be built here. The support structure consists of 798 support structures for mirror segments, which together form the main mirror (with a diameter of over 39 metres) of the telescope. The order, which VDL ETG Projects will deliver over a period of about five years, involves several tens of millions of euros.
At the headquarters of the European Southern Observatory, in Garching bei Munich in Germany, ESO director general Xavier Barcons and VDL Groep president Willem van der Leegte signed the contract for the order last week. Willem van der Leegte: "Great that ESO awarded us this prestigious order, this is the first time a contract of this size in the field of astronomy has gone to a Dutch party. This project is a great calling card for the European high-tech supply industry. It allows VDL Groep to further raise its profile as a high-tech player and means a springboard to our involvement in more of ESO's new telescopes being built worldwide."
'Largest eye on the sky'
The size of the ELT is comparable to that of a football stadium. The telescope's 'eye' is almost as big as half a football field and will capture more light than all the large, professional optical telescopes currently combined do. The ELT will enable scientific discoveries on planets, the composition of nearby galaxies and the deep universe. The hexagonal, mechatronic support structure keeps the telescope's main mirror in the desired shape continuously, with nanometre precision. VDL ETG Projects is handling the construction of these structures. The design was created together with TNO, supported by NOVA (Dutch Research School for Astronomy). The main mirror with adaptive control system will thus be the largest telescope for observations in visible light.
It is impossible to make the 39-metre main mirror in one piece, so the mirror will be constructed from 798 hexagonal mirror segments about 1.4 metres tall and 5 centimetres thick. Each mirror segment has its own support structure and is driven by several electric motors, allowing very precise positioning of the mirror. Continuous correction is done by 9 electric motors on each frame and 3 electric motors under each frame. To be coated with a new reflective layer, mirrors have to be replaced regularly. Therefore, a total of almost 950 mirror segments and support structures are built.
A sum of over one billion euros has been made available for the realisation of the ELT. Construction of the ELT's foundation has already started. By 2024, the telescope should be operational.
Dutch collaboration
VDL ETG Projects has been working on ELT for just under a decade. In 2010, the first prototypes were made with TNO for the support structure for the telescope. Four years later, in 2014, VDL and TNO won a contract with NOVA to design the final prototype support structures and build six frames. TNO uses its experience in optical instrumentation and precision mechanics for aerospace, astronomy and semiconductor industries to design and test structures to be positioned at the nanometre scale (one millionth of a millimetre). VDL ETG, also with extensive experience in the semiconductor industry, analytical and a Science & Technology segment, has particular expertise in optimising precision mechatronic system designs for cost control, reliability and maintenance. All this to economically mass-produce the final design. NOVA, the consortium of astronomers from Dutch universities, has specialist knowledge of using large telescopes and optimising the interaction between the telescope and the scientific instrumentation behind it. Together, they assure ESO of optimal synergy between the above-mentioned important disciplines. Today's order, awarded to VDL ETG Projects, thus includes the series production of the support structure.
ESO
ESO is the leading intergovernmental astronomical organisation in Europe and by far the most prolific observatory in the world. This European Southern Observatory is supported by 15 member states: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, as well as host country Chile. ESO runs an ambitious programme aimed at designing, building and managing large observatories that enable astronomers to make important scientific discoveries.
