🛰️ Gravitational waves: LISA construction begins!

LISA is the major ESA scientific mission that will observe the Universe by detecting the gravitational waves that traverse it in a very rich but previously unexplored frequency range.

Gravitational waves are vibrations of spacetime created by certain phenomena involving extreme masses. The emission of gravitational waves intense enough to be detected requires the gravitational interaction of extremely dense objects such as black holes, neutron stars, white dwarfs, and even more exotic objects present in the early Universe.


Thanks to a constellation of three satellites forming an equilateral triangle with sides of 2.5 million kilometers (about 1.55 million miles) (6 times the Earth-Moon distance) in orbit around the sun, LISA will detect the tiny deformations of spacetime caused by the passage of these waves.

Since 2015, mergers of stellar-mass black holes and neutron stars have been regularly observed by the ground-based LIGO and Virgo instruments, and since 2023 a gravitational wave signal seems to be detected at a very low frequency (the nano Hz or once per billion seconds, whereas Hz corresponds to a frequency of once per second) thanks to the pulsar timing array.

LISA will observe in the millihertz range where many sources emit, such as mergers of supermassive black hole binary systems with masses of the order of a million solar masses, extreme mass ratio binary systems (a small black hole orbiting a supermassive black hole, for example), binary systems of neutron stars, and potentially the stirrings of the early Universe. LISA will observe these sources with such a level of detail that it will be possible not only to do astrophysics but also fundamental physics and cosmology.

Cutting-edge technology

To detect the tiny deformations of the triangle formed by the satellites during the passage of gravitational waves, the satellites exchange laser beams and use interferometry to measure the variations in the distance separating them with an accuracy of about ten picometers (100 times smaller than the size of an atom).

This is a huge challenge because, to detect gravitational waves, the satellites must be sensitive only to gravity. To achieve this, each satellite protects reference masses, small gold-platinum cubes with sides of 4 cm (about 1.6 inches) without any mechanical contact, which are thus "in free fall." The satellite measures, by interferometry and capacitive coupling, its position relative to the cubes it contains and repositions itself using a set of micro-thrusters, thereby countering any non-gravitational perturbation (micro-meteorites, solar particles, etc.).

Industrial partnerships and mission timeline

The interferometric system and the readjustment system on the reference masses constitute the heart of the scientific instrument. It is being developed under ESA coordination by European states with a contribution from NASA. The realization of the rest of the satellite (structure, solar panels, propulsion, on-board computers, etc.) is entrusted to OHB System in partnership with Thales.

The signing of this contract finalizes the phase of setting up the organization and marks the beginning of the construction of LISA. The launch of the 3 satellites is planned for 2035 by an Ariane 6.4 rocket. It will be followed by a transfer phase of 18 months to reach the final orbits and begin scientific operations, which will last at least 4 years.