Laser Interferometer Space Antenna

The Laser Interferometer Space Antenna (LISA) is a planned European space mission to detect and measure gravitational waves—tiny ripples in the fabric of spacetime—from astronomical sources. LISA will be the first dedicated space-based gravitational-wave observatory. It aims to measure gravitational waves directly by using laser interferometry. The LISA concept features three spacecraft arranged in an equilateral triangle with each side 2.5 million kilometers long, flying in an Earth-like heliocentric orbit. The distance between the satellites is precisely monitored to detect a passing gravitational wave.

The LISA mission is designed for direct observation of gravitational waves, which are distortions of spacetime travelling at the speed of light. Passing gravitational waves alternately squeeze and stretch space itself by a tiny amount. Gravitational waves are caused by energetic events in the universe and, unlike any other radiation, can pass unhindered by intervening mass. Launching LISA will add a new sense to scientists' perception of the universe and enable them to study phenomena that are invisible in normal light.

Potential sources for signals are merging massive black holes at the centre of galaxies, massive black holes orbited by small compact objects, known as extreme mass ratio inspirals, binaries of compact stars, substellar objects orbiting such binaries, and possibly other sources of cosmological origin, such as a cosmological phase transition shortly after the Big Bang, and speculative astrophysical objects like cosmic strings and domain boundaries.