LISA is a space mission led by ESA with contributions from NASA and many ESA member states. LISA will observe gravitational waves in space with three satellites connected by laser beams forming a constellation in a heliocentric orbit.

The ground-based LIGO and Virgo observatories have already observed many black hole collisions and at least one neutron star collision since the first gravitational wave detecion in 2015. Current ground-based observatories can observe gravitational waves with short wavelengths only because their laser arms are less than 5 km long.bBut the laser arms of LISA will be millions of kilometers long. LISA can detect gravitational waves with long wavelengths from sources that can't be observed on the ground like the mergers of massive black holes in galactic centres or gravitational waves from the Big Bang.

LISA will launch in 2034. The three satellites will form a high precision interferometer that senses gravitational waves using lasersnby monitoringextremely small distance changes between free falling test masses inside the spacecraft. LISA needs many new key technologies to work including high-end optics, lasers and micro-thrusters. This technology was successfully tested with LISA Pathfinder. LISA Pathfinder performance exceeded all expectations!

LISA will observe gravitational waves together with the ground-based observatories and gather revolutionary information about the dark universe and will break new ground in the era of multi-messenger astronomy.