Laser Interferometer Space Antenna

The Laser Interferometer Space Antenna (LISA) is a proposed space mission concept designed to detect and accurately measure gravitational waves from astronomical sources. It is currently not funded by any space agency; however, a proof-of-concept mission, LISA Pathfinder, designed to demonstrate the technology necessary for a successful full mission is due for launch in 2014.

The LISA was previously a joint effort between the United States space agency NASA and the European Space Agency (ESA). However, on April 8th 2011, NASA announced that it would likely be unable to continue its LISA partnership with the European Space Agency, due to funding limitations. ESA began a full revision of the mission's concept and renamed it as The New (or Next) Gravitational wave Observatory (NGO). It was one of the three candidates for the first (L1) Cosmic Vision L-class mission but it lost to the Jupiter Icy Moon Explorer (JUICE). It may be a candidate for the next L-class mission.

If launched, LISA will be the first dedicated space-based gravitational-wave detector; it will measure gravitational waves by using laser interferometry to monitor the fluctuations in the relative distances between three spacecraft, arranged in an equilateral triangle with 5 million kilometer arms, and flying along an Earth-like heliocentric orbit. Passing gravitational waves create oscillations in the inter-spacecraft distances, as measured by light, in directions transverse to the direction of wave propagation. LISA will be sensitive to waves in the frequency band between 0.03 millihertz to 100 millihertz, including signals from massive black holes that merge at the center of galaxies, or that consume smaller compact objects; from binaries of compact stars in our Galaxy; and possibly from other sources of cosmological origin, such as the very early phase of the Big Bang, and speculative astrophysical objects like cosmic strings and domain boundaries.