Artist's impression of the LISA "mother" spacecraft showing the two laser arms.
The LISA mission consists of one “Mother” and two “Daughter” spacecraft orbiting the Sun in a triangular configuration. The three satellites are separated by a distance of 1 Mio km. The spacecraft are connected by laser beams forming the arms of a high precision laser interferometer. This interferometer senses gravitational waves by monitoring the changes in distance between free falling test masses inside the spacecraft.