LISA Pathfinder

LISA Pathfinder was an ESA-led mission that tested free-fall, laser interferometry and drag-free control near Sun–Earth L1 for future space-based gravitational-wave astronomy. Its European LISA Technology Package measured the relative motion of two gold-platinum test masses while microthrusters kept the spacecraft centered around them. NASA’s ST7 Disturbance Reduction System separately demonstrated colloid microthrusters and alternative control laws using measurements from the European sensors. The mission tested the technologies needed for LISA rather than observing astrophysical gravitational waves.