Edwin Valentijn: ‘If you’ve ever worked on an experiment like this, a successful launch is an indescribable experience.’ Photo by Reyer Boxem

Looking for dark energy

A decade of waiting for space

Edwin Valentijn: ‘If you’ve ever worked on an experiment like this, a successful launch is an indescribable experience.’ Photo by Reyer Boxem
For ten years, astronomer Edwin Valentijn worked on the data-processing system that was going to go into space on the Euclid space telescope. But then, the Russian invasion of Ukraine messed everything up.
By Martijn Luinstra
18 April om 14:48 uur.
Laatst gewijzigd op 18 April 2023
om 14:48 uur.
April 18 at 14:48 PM.
Last modified on April 18, 2023
at 14:48 PM.

It’s not like delays are unusual in the aerospace business. In fact, they happen all the time. ‘It’s always a big deal’, says astronomer Edwin Valentijn. ‘Even if you do know that it’s a possibility.’ 

But when Valentijn’s brainchild, a data-processing system for space telescope Euclid, was at risk of suffering a four-year delay, he started to get seriously worried. ‘I can’t retain people for that long and I’d lose expertise. Plus, there’s also the competition.’

What’s causing this particular misfortune? The Russian invasion of Ukraine. After ten years, the telescope was ready to be launched by a Russian Soyuz rocket, but then Russia withdrew in response to the European sanctions. ‘It was awful. We were ready to launch, but we didn’t have a rocket.’

Dark matter

Euclid will be studying dark matter and dark energy. Dark matter is matter that we cannot perceive, but which astronomers think exists. Calculating the mass of stars based on what we can see, they are much too light to explain the movements happening in space. That means there has to be something we can’t see. 

Dark energy is something else: it involves the distances between star systems, which are getting bigger. The universe is expanding, at an accelerating rate. Astronomers don’t know why this is happening. They’ve named the force behind this acceleration ‘dark energy’. But for now, it remains an unsolved problem, the holy grail of astronomy and physics, according to Valentijn. 

We were ready to launch, but we didn’t have a rocket

Euclid will be making observations that will help exclude various theories on the nature of either phenomenon and it might even help to figure out the correct one. ‘We have a lot riding on Euclid.’

Not only can it distinguish just as many details as the famous Hubble telescope, it’s also five thousand times faster. Euclid takes ninety minutes to study an area in space the size of the moon, while this takes Hubble 250 days. During its mission, Euclid will be able to map approximately 30 percent of the sky. ‘It takes amazing photos of the entire cosmos, capturing every little detail’, says Valentijn.

This leads to many, many petabytes of information that need to be processed (a petabyte is a thousand terabytes). That’s where Valentijn comes in: together with a large international team, he created Euclid’s data-processing system.

Drawing board

The astronomer became involved in the project when it was still on the drawing board fifteen years ago. ‘After a knock-out race that started out with fifty-five proposals, we ended up presenting our project in this Idols-like grand final in Paris in 2012’, he recalls. ‘ESA, the European space agency, only had enough money to fund one or two projects. Our proposal for data processing is what convinced the jury.’

Building the data-processing system was the perfect job for Valentijn: he’d been working on it for a long time. In 2000, he worked on the VLT Survey Telescope in Chile, which at the time was the fastest wide-angle-lens telescope in the world. Valentijn was responsible for creating a system that would process, analyse, and archive the images. There, he laid the foundation for an all-in-one solution he called AstroWISE.

AstroWISE saw first light after two years of work: the first photo of a new IT telescope. Valentijn still has the picture hanging in his office. Rather than a giant star system or colourful interstellar gas cloud, it’s a diagram of the software components in the AstroWISE system that shows how they were connected for the first time. 

‘When someone does something in, say, Naples, we see it happening here in real time. It’s like booking a plane ticket, but in an extremely complex system twenty layers deep’, says Valentijn. ‘And it worked!  You can take a photo, if you want. I’m so proud of it.’

Edwin Valentijn during a visit to Thales Alenia Space in Cannes, with the Euclid satellite almost ready to ship to Cape Canaveral.


Unfortunately, the VLT Survey Telescope wasn’t finished yet. The large mirror, the telescope’s most important optic element, got broken during transport, which delayed its completion by years. 

Valentijn had to go looking for new projects that could use his AstroWISE. He participated in projects such as LOFAR (a radio telescope made up of thousands of radio antennae) and the UMCG’s Lifelines project, as well as projects set up by private businesses. ‘I became an expert in big data even before that was a thing.’

This also made him the perfect partner for the Euclid project. When the ESA team realised his telescope would provide more data than any other scientific telescope in the world, they asked him for help, making the AstroWISE concept the centrepiece of the project. 

Valentijn has to wait once more for a telescope, but he never once considered giving up. ‘It’s hard, but it’s absolutely still worth it.’

The people around me said I was practically floating

The astronomer thinks this is the only way to find a good explanation for dark matter and dark energy. ‘The only way to do this is to add the signal of not thousands, not tens of thousands, not hundreds of thousands, but millions of star systems and apply statistics to the data’, he says.


Fortunately, Valentijn recently got good news: they found a new rocket. American company SpaceX is providing a Falcon 9 rocket that will launch Euclid in July. ‘We’re so happy it all worked out. We still can’t believe it.’

The exact launch date hasn’t been determined yet, but it will be an exciting day for everyone involved in the project. ‘If you’ve ever worked on an experiment like this, a successful launch is an indescribable experience’, says Valentijn. 

He’s seen it happen once before, in 1995, when the Infrared Space Observatory, that the UG was involved in, was launched. ‘I didn’t realise it myself, but the people around me said I was practically floating.’ 

But the telescope’s launch is only the beginning. After that, it will take a few months before Euclid will start sending pictures of the cosmos. ‘First, it has to go through all these technical rituals’, he says. The telescope first has to make contact with all the ground stations on earth, after which astronomers get to fine-tune all the instruments. Only then can the telescope start taking pictures.

Euclid’s first look at the universe is then sent to Valentijn’s data-processing system. The UG’s CIT is one of the important data centres involved in the process. For the astronomer, this moment might be even more important than the launch. ‘The first light moment is incredible as well. The only thing better is the birth of your first child.’