future view

Will the Netherlands help to build the world's largest telescope?

13 June 2017 • 5 min reading time

The European Southern Observatory (ESO) is working on the world's largest reflecting telescope: the European Extremely Large Telescope (E-ELT). The support structure for the telescope’s 798 mirror segments was designed by a consortium consisting of TNO, the VDL Enabling Technologies Group (VDL ETG; a high-tech company based in the province of Brabant) and the Netherlands Research School for Astronomy (NOVA). ESO will use a procurement procedure to decide who will actually turn this design into a reality. One thing is certain: if the Netherlands goes ahead with this, it will have a positive impact on our economy.

The E-ELT, which is scheduled for completion in 2024, will be almost as large as a football stadium. The primary mirror consists of 798 hexagonal mirror segments, and is no less than 39 metres in diameter. By way of comparison, its precursor, the European Very Large Telescope, has a total of four mirrors, each 8.2 metres in diameter. The new telescope is to be built at a site on the Cerro Armazones, a 3,064 metre-high mountain in Chile. On Friday 26 May, Michelle Bachelet Jeria – the President of Chile – laid the first stone for the construction of the E-ELT.

Black holes, supernovae and exoplanets

The purpose of the E-ELT is to study the universe in greater detail than is possible even with today’s advanced technology, and to make further discoveries about black holes, supernovae and exoplanets. The sheer size of the telescope means that it can capture more light and thus achieve better quality results. It can reveal more objects and finer details than ever before, bringing distant planets into even sharper focus. The E-ELT will be used to study the very first stars and galaxies in the universe, as well as the atmospheric composition of Earth-like planets orbiting other stars. This will give a great boost to astrobiologists, as they search for life elsewhere in the universe.

Exceptional design

The telescope’s primary mirror rests on a support structure that was designed in the Netherlands: It was developed by TNO, in cooperation with VDL ETG and NOVA. Two designs were submitted to ESO (one by the Spanish company CESA and one by TNO), and the Dutch design best fulfilled the requirements. In particular, the quality of the mechanism that controls the shape and positioning of each individual mirror segment is just one of the exceptional features of this design. The forces acting on the mirror change constantly as the telescope rotates. During this process, the pull of gravity would normally distort the mirror into a series of slightly different shapes. The current design’s highly sophisticated balancing system provides perfect support, thus compensating for the effects of gravity. “Large-diameter mirrors make telescopes more powerful, but they are also more likely to develop tiny distortions due to gravity”, says Matthew Maniscalco, an American business developer at TNO. “These distortions reduce the sharpness of the telescope’s images. The support structure we have designed is capable of positioning the mirrors to an accuracy of 25 nanometres.” To give you an idea of what this means, if you were to peel the ultra-thin plastic of a sandwich bag into 2,000 equal layers, the thickness of one such layer would correspond to this level of accuracy.

Spiritual father

The final qualification units are currently being tested. After that test phase has been completed, construction work on the support structures can commence. ESO will use a procurement procedure to decide who will get the contract. At first glance, the Dutch consortium would appear to be far ahead of the competition. “We are the spiritual fathers of this design, we know it like the back of our hand”, says Hans Priem, Science & Technology Business Manager at VDL ETG. “We have considerable experience in the management of extremely complex products, for use in remote locations, and to tight deadlines. In addition, we are a financially robust partner with a solid and reliable reputation.” According to Mr Priem, the partnership with TNO makes the consortium an obvious choice for the ESO. “A system consisting of 798 complex and interconnected components is inevitably going to experience some teething troubles. Here, the ability to make quick and flexible adjustments is absolutely vital. At times like that, our partnership with TNO and NOVA delivers great added value. Ultimately, this will limit the technical risks for ESO”, says Hans Priem. He is also referring here to ‘active correction’, another great advantage of the consortium’s design. This can compensate for minor manufacturing defects and design shortcomings in the mirror’s support mechanism. Aside from its positive impact on accuracy, this is a kind of insurance for ESO. With complex instruments like this, unintentional design and construction errors can always creep in. Now, however, there is a way of actively compensating for them. This offers a huge advantage over the Hubble Space Telescope, for example, where extremely expensive repair work in space was needed to correct its ‘short-sightedness’.

“We are the spiritual fathers of this design, we know it like the back of our hand”

Enormous impact on Dutch businesses

Nevertheless, according to Mr Maniscalco, waiting to see who gets the contract is still a bit nerve-wracking. Many different points are taken into consideration, and quality is not always the only determining factor. If the Dutch consortium wins the tender, this will have an enormous impact on the country’s economy. At least 25 million euros will go to Dutch suppliers. However, according to Matthew Maniscalco, there would also be a major indirect effect. “If we construct a major component of the largest high-precision reflecting telescope in the world, it will boost the Netherlands’ international reputation as a knowledge economy. In addition, the better the equipment we manufacture, the more valuable data we generate for our scientists.”

Politicians give a helping hand

Mr Priem also emphasizes the indirect effects of winning this tender. “The Netherlands has a poor track record when it comes to winning European tenders of this kind. If we succeed, this will show other Dutch companies that it really can be done. It will also show the world that we are capable of managing such a big project from the Netherlands.” Winning the tender requires more than arranging for the consortium partners to cooperate on the practical aspects involved. Politicians, too, will have to put their best foot forward. “This time, the ministries of Foreign Affairs, Economic Affairs, and Education, Culture and Science are helping to tackle the project. That is the only way you’ll have a chance of winning a big tender.”

“If we construct a major component of the largest high-precision reflecting telescope in the world, it will boost the Netherlands’ international reputation as a knowledge economy”


Whichever way it goes, Mr Maniscalco still talks about the journey involved with evident pride. “This is exactly why TNO was created in the first place. Complex projects like this involve a huge amount of preparatory research. New technologies and materials must be extensively tested before they can be used in practice. TNO helps companies through this initial phase. Fascinating projects that generate effective solutions, that’s what energizes everyone here.”

This TNO project supports the following Sustainable Development Goals

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