The Laser Interferometer Space Antenna (LISA) is a planned European space mission to detect and measure gravitational waves—slight 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 relative acceleration between the satellites is precisely monitored to detect a passing gravitational wave, which are distortions of spacetime traveling at the speed of light.