The Space-Based Gravitational Wave Interferometer

LISA will be a constellation of at least three spacecraft forming a giant equilateral triangle across the solar system. All of these components would be in separate orbits around the sun, and they would effectively act like a laser interferometer with a baseline of millions of kilometers. The reason LISA would be able to reach that kind of sensitivity is because of the huge reduction of background noise that you get when you build your interferometer in space instead of on earth.