Green light for Dutch contribution to space detector LISA

20 February 2023

A Dutch consortium led by SRON has received a twelve million Euro NWO grant that will enable it to become a key partner within ESA/NASA’s LISA mission, the first space detector for gravitational waves. Nikhef is co-building the instruments.

The Laser Interferometer Space Antenna (LISA) consists of three spacecraft that will fly around the Sun after the Earth starting in 2035. By continuously measuring their mutual distances with laser beams, they detect gravitational waves from the universe. In space, LISA can extend its arms up to 2.5 million kilometers, detecting longer wavelengths than ground-based detectors.

This allows researchers to “listen” for the first time to, for example, the Big Bang or baby black holes from the early universe. Or to the chaotic paths stars take as they are swallowed up in the complex geometry around a supermassive black hole, like a practical test of Einstein’s General Theory of Relativity.

LISA’s eyes

As consortium leader, space research institute SRON will work with Nikhef, Radboud, Leiden University, UvA, Utrecht University, TNO, Maastricht University and RUG to build the photodiodes (LISA’s ‘eyes’), software, the targeting mechanism and the associated readout electronics.

That aiming listens extremely closely because each laser has to hit a lens at a distance of 2.5 million kilometers. Light takes eight seconds to do that. For comparison: if a dime falls from the Eiffel Tower, a laser from the Netherlands has to aim exactly where that dime will be in eight seconds.

The photodiodes don’t have it much easier. They must detect laser beams of originally 1 watt, like a table lamp, but which after their journey have been toned down to 250 picoWatts, i.e. over a billion times weaker.

Piece of art

The development of the software is a piece of art in itself. It must distinguish between the multitude of gravitational waves from all possible directions that continuously vibrate the spacecraft at different frequencies and amplitudes.

‘A Dutch contribution to LISA is of great importance,’ says Gijs Nelemans, one of the leaders of the LISA-NL consortium. ‘Dutch scientists are building unique expertise with it, and the access to all the data gives us a head start on the only access route to a whole new field.’

Einstein Telescope

The institutes involved are building up knowledge and expertise in the development of such precise techniques as mechatronics, semiconductor technology and low-noise electronics. This also further substantiates their candidacy to build the Einstein Telescope together with German and Belgian partners, in the border region of the Netherlands with Belgium and Germany.

In total, NWO gave the green light to nine proposals for new research infrastructure. Together these involve 140 million euros.