The Laser Interferometer Space Antenna (LISA) consists of three spacecraft that will be orbiting the Sun, trailing behind Earth, from 2035 onwards. By continuously measuring their mutual distances using laser beams, they detect gravitational waves from the Universe. In space, LISA is able to stretch her arms to 2,5 kilometers, making her susceptible to longer wavelengths than ground-based detectors.
It allows us to ‘listen’ for the first time to for example the Big Bang or baby black holes from the early Universe. Or to the chaotic orbits of stars as they are being engulfed in the complex geometry around a supermassive black hole, as a practical exam for Einstein’s general theory of relativity.
As consortium leader, SRON Netherlands Institute for Space Research will, together with Nikhef, Radboud, Leiden University, UvA, Utrecht University, TNO, Maastricht University and RUG, build the photodiodes (LISA’s ‘eyes’), software, pointing mechanism and corresponding readout electronics.
In this case pointing is an extreme sport, because each laser needs to hit a lens at 2.5 million kilometers distance, which takes light eight seconds. For comparison: if a dime falls down from the Eiffel Tower, a laser beam from The Netherlands must aim exactly at the spot where that dime will be in eight seconds.
For the photodiodes things are not much easier. They must detect the laser beams of originally 1 Watt, like a table lamp. But after their journey those will have been reduced to 250 picoWatt, more than a billion times weaker than said lamp.
The development of the software is more complex compared to conventional telescopes. It has to 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 for The Netherlands,' says Gijs Nelemans, one of the leaders of the LISA-NL consortium. 'Dutch scientists build up unique expertise, and access to all data gives us a head start on the only entrance route to an entirely new field.'
The institutes involved build up knowledge and skills in the development of this type of precision technology, such as mechatronics, semiconductor technology and low-noise electronics. This underlines their candidacy to build the Einstein Telescope together with German and Belgian partners, in the border region of The Netherlands with Belgium and Germany.