page_title: Laser Interferometer Space Antenna
hierarchical_section_title: Laser Interferometer Space Antenna
caption_attribution_description: English: NASA illustration of LISA, taken from http://lisa.jpl.nasa.gov/gallery/lisa-waves.html. High resolution TIFF compressed with "cjpeg" from libjpeg-progs. NASA's description: The three LISA spacecraft will be placed in orbits that form a triangular formation with center 20° behind the Earth and side length 5 million km. (The figure showing the formation is not to scale.) Each spacecraft will be in an individual Earth-like orbit around the Sun. The orbits are chosen to minimize changes in the lengths of the sides of the triangle. The orbits of the three spacecraft have a relationship between inclination and eccentricity that inclines the plane of the formation by 60° with respect to the ecliptic. The nodal longitudes of the three orbits are shifted by 120° to create the triangle. The heliocentric orbit offers a particularly quiet environment, critical for the control of disturbances on the test masses defining the interferometer arms. The test masses are free-falling and shielded by the enclosing spacecraft from disturbances of the solar wind and photon pressure. The orientation of the spacecraft with respect to the Sun changes very slowly. The Sun appears moves along a cone with a 30° half angle aligned with the spacecraft's cylindrical axis once per year, giving constant illumination. The major source of disturbance in the measurement band is the variation in the solar constant caused by the Sun's normal modes of oscillation, amounting to less than 10 ppm in intensity. The orbital motion of the antenna sweeps its sensitivity lobes across the sky, giving an amplitude modulation dependent on a source's angular coordinates. Similarly, the Doppler effect gives a phase modulation dependent on a source's angular coordinates. The two effects combine to give directional information about every source. Most of the sources observable by LISA are periodic or quasi-periodic and can be observed for at least a year. The angular position accuracy depends on the signal-to-noise ratio. For the strongest sources, the direction to the source can be determined to about 1 arc minute.
context_page_description: The Laser Interferometer Space Antenna is a mission led by the European Space Agency to detect and accurately measure gravitational waves—tiny ripples in the fabric of space-time—from astronomical sources. LISA would be the first dedicated space-based gravitational wave detector. It aims to measure gravitational waves directly by using laser interferometry. The LISA concept has a constellation of three spacecraft arranged in an equilateral triangle with sides 2.5 million km long, flying along an Earth-like heliocentric orbit. The distance between the satellites is precisely monitored to detect a passing gravitational wave.
  The LISA project started out as a joint effort between the United States space agency NASA and the European Space Agency ESA. However, in 2011, NASA announced that it would be unable to continue its LISA partnership with the European Space Agency due to funding limitations. The project is a recognized CERN experiment. A scaled down design initially known as the New Gravitational-wave Observatory was proposed for ESA's Cosmic Vision L1 mission selection.
context_section_description: The Laser Interferometer Space Antenna (LISA) is a mission led by the European Space Agency to detect and accurately measure gravitational waves—tiny ripples in the fabric of space-time—from astronomical sources. LISA would be the first dedicated space-based gravitational wave detector. It aims to measure gravitational waves directly by using laser interferometry. The LISA concept has a constellation of three spacecraft arranged in an equilateral triangle with sides 2.5 million km long, flying along an Earth-like heliocentric orbit. The distance between the satellites is precisely monitored to detect a passing gravitational wave.
  The LISA project started out as a joint effort between the United States space agency NASA and the European Space Agency ESA. However, in 2011, NASA announced that it would be unable to continue its LISA partnership with the European Space Agency due to funding limitations. The project is a recognized CERN experiment (RE8). A scaled down design initially known as the New Gravitational-wave Observatory (NGO) was proposed for ESA's Cosmic Vision L1 mission selection. In 2013, ESA selected 'The Gravitational Universe' as the theme for its L3 mission in the early 2030s. whereby it committed to launch a space based gravitational wave observatory.
  In January 2017, LISA was proposed as the candidate mission. On June 20, 2017 the suggested mission received its clearance goal for the 2030s, and was approved as one of the main research missions of ESA.
  The LISA mission is designed for direct observation of gravitational waves, which are distortions of space-time travelling at the speed of light. Passing gravitational waves alternately squeeze and stretch objects by a tiny amount. Gravitational waves are caused by energetic events in the universe and, unlike any other radiation, can pass unhindered by intervening mass. Launching LISA will add a new sense to scientists' perception of the universe and enable them to study phenomena that are invisible in normal light.
  Potential sources for signals are merging massive black holes at the centre of galaxies, massive black holes orbited by small compact objects, known as extreme mass ratio inspirals, binaries of compact stars in our Galaxy, and possibly 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.
caption: Artist's conception of LISA spacecraft
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