LISA

Three spacecraft in a triangle with 2.5 million km arms, trailing Earth around the Sun, exchanging laser links to measure picometre changes in the separations of free-falling test masses. Sensitive from 0.1 mHz to 1 Hz: mergerscompact binary coalescenceThe inspiral and merger of two black holes, two neutron stars or one of each. The signal sweeps up in frequency and amplitude (a chirp) until the objects merge; its shape gives their masses, spins and distance. of massive black holes out to high redshiftredshiftz = λ_observed/λ_emitted − 1, the stretching of light by cosmic expansion (or by recession). For distant sources it stands in for distance and look-back time: z ≈ 1 is about 8 Gyr ago, z ≈ 10 about 13.3 Gyr., extreme-massarcsecond1/3600 of a degree (″). A milliarcsecond (mas) is 10⁻³″ and a microarcsecond (µas) 10⁻⁶″. Atmospheric seeing limits ground telescopes to about 0.5–1″ without adaptive optics.-ratio inspirals, and Galactic white-dwarf binaries. An ESA L-class mission with NASA, adopted in 2024.

Operator

ESA, NASA

Orbit

Earth-trailing solar orbit

Frequency band

0.1 mHz – 1 Hz

Messenger

Gravitational waves

Launch

2035 (target)