The first space observatory designed to detect gravitational waves will undergo serious examination and the construction of flight equipment will begin. On January 25, ESA (European Space Agency) announced that the Space Laser Interferometer Antenna LISA has been officially accepted into its mission range, with launch planned for the mid-2030s. ESA manages the mission and NASA is the collaborative partner.

“In 2015, the ground-based LIGO observatory opened a window into gravitational waves, the perturbations that permeate space-time, the fabric of our universe,” said Mark Clampin, director of the Astrophysics Division at NASA Headquarters in Washington. “LISA will give us a panoramic view and allow us to observe a wide variety of resources both within our galaxy and far beyond. We are proud to join this international effort that aims to open new ways to explore the mysteries of the universe.”

NASA will provide several key components of the LISA instrumentation suite, as well as science and engineering support. NASA’s contributions include lasers, telescopes, and devices that reduce interference from electromagnetic charges. LISA will use this equipment to measure distance changes caused by gravitational waves millions of kilometers away in space. ESA will provide the spacecraft and supervise the international team during mission development and operation.

Gravitational waves were predicted more than a century ago by Albert Einstein’s theory of general relativity. They are formed by the acceleration of masses, such as a pair of black holes in orbit. As these waves consume orbital energy, the distance between objects gradually narrows over millions of years and they eventually merge.

These ripples in the fabric of space went unnoticed until 2015, when LIGO, the Laser Interferometer Gravitational-Wave Observatory funded by the US National Science Foundation, measured gravitational waves resulting from the merger of two black holes. This discovery led to the emergence of a new field of science called “multimessage astronomy,” in which gravitational waves can be used in conjunction with other cosmic “messengers” (light and particles) to observe the universe in new ways.

LIGO, among other ground-based facilities, has observed the mergers of neutron stars and systems of neutron stars and black holes, as well as dozens more black hole mergers. Black holes detected using gravitational waves so far have been relatively small; Their masses were perhaps hundreds of times that of our Sun. But scientists believe that merging of much larger black holes was common when the universe was young, and that only a space observatory would be sensitive to the gravitational waves coming from them.

“LISA was designed to detect low-frequency gravitational waves that cannot be detected by instruments on Earth,” said Ira Thorpe, mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “These sources include tens of thousands of small binary systems in our galaxy, as well as massive black holes that merged during galaxy collisions in the early universe.”

LISA will consist of three spacecraft that will follow the Earth in its orbit around the Sun, flying in a large triangle shape. Each arm of the triangle stretches 1.6 million miles (2.5 million kilometers). The spacecraft will monitor internal test masses affected only by gravity. They will also continuously fire lasers to precisely measure their fission down to a size smaller than the size of a helium atom. Gravitational waves from sources in the universe will create fluctuations in the arm lengths of the triangle, and LISA will record these changes.

The basic measurement technology was successfully demonstrated in space by ESA’s LISA Pathfinder mission, which operated between 2015 and 2017 and involved NASA. The spacecraft demonstrated the excellent control and precise laser measurements required for LISA.