Meet LISA

The LISA mission will push our understanding of cosmic physics to new heights by revealing a currently undetectable sea of low-frequency gravitational waves. These ripples in space-time carry detailed information about massive objects and extreme events across the cosmos.

The LISA mission consists of three spacecraft flying in a vast triangular formation that follows Earth as it orbits the Sun. Each arm of the triangle stretches 1.6 million miles (2.5 million kilometers) — large enough that the Sun itself could fit snugly inside the constellation.

Each spacecraft will carry two, Rubik's-cube-sized, free-floating cubes called proof masses inside it, and all three spacecraft will be connected to each other via beams of light produced by lasers. These beams will monitor the distance between the cubes and look for changes smaller than the diameter of a hydrogen atom.

Gravitational waves arriving from throughout the universe will minutely change the lengths of the triangle’s arms. Computers on the ground will search through these measurements to identify individual gravitational wave events and extract information on the source’s location and physical properties.

The LISA mission builds on the work of facilities like the National Science Foundation’s ground-based LIGO (Laser Interferometer Gravitational-wave Observatory) and the ESA-led LISA Pathfinder mission, in which NASA participated.

NASA’s Contributions

The LISA mission is led by ESA, with NASA serving as a collaborative partner. NASA will supply four key elements for LISA:

• Laser systems provide light beams that connect the three spacecraft for the detection of gravitational waves.

• Telescope systems transmit and receive the laser light across the 1.6 million miles (2.5 million kilometers) between spacecraft.
• Charge management devices reduce the buildup of electric charge on the free-floating proof mass inside each spacecraft.
• Data analysis systems for identifying and characterizing individual gravitational wave signals from LISA.

NASA will also support ESA with scientific and systems engineering expertise.

LISA Science

Massive objects generate gravitational waves when they accelerate, like when two black holes orbit each other. These ripples in space-time move at the speed of light and are unaffected by objects they encounter on their way to us.

Astronomers have traditionally relied on different kinds of light to tell them about what’s happening in the universe. Gravitational waves, however, provide information that light can’t, so studying both gives a clearer picture. This combined approach is part of what scientists call multimessenger astronomy.

Gravitational waves were a prediction that came out of Albert Einstein’s general theory of relativity, which was published over 100 years ago. However, scientists didn’t have the technology to observe them directly until a 2015 detection using ground-based observatories. The vast scale of LISA will open a new window on a previously unstudied sea of these space-time ripples that cannot be observed from Earth’s surface.