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The Evolved Laser Interferometer Space Antenna (eLISA), previously called LISA, is a proposed European Space Agency mission designed to detect and accurately measure gravitational waves — tiny ripples in the fabric of space-time — from astronomical sources. The mission would evolve from the ESA LISA Pathfinder technology research demonstrator scheduled for launch in December 3, 2015 into a full scale gravitational wave observatory.〔 〕 eLISA 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 million kilometre arms (5 million km for classic LISA, 1 million km for eLISA) flying along an Earth-like heliocentric orbit. The distance between the satellites is precisely monitored to detect a passing gravitational wave.〔 The LISA project (Laser Interferometer Space Antenna) was previously a joint effort between the United States space agency NASA and the European Space Agency ESA. However, on April 8, 2011, NASA announced that it would be unable to continue its LISA partnership with the European Space Agency due to funding limitations. ESA has therefore revised the mission's concept to fit into a European-only cost envelope. The scaled down design was initially known as the New Gravitational-wave Observatory (NGO) for ESA's L1 mission selection. Following this unsuccessful application, the name was changed to eLISA.〔(Selected: The Gravitational Universe ESA decides on next Large Mission Concepts ).〕 The project was chosen as the L3 mission within the ESA Cosmic Vision Program, with a tentative launch date in 2034.〔 A LISA-like mission is designed to directly observe 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 eLISA will add a new sense to scientists' perception of the universe and enable them to listen to a world that is invisible with 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. ==Mission description== The LISA/eLISA Mission’s primary objective is to detect and measure gravitational waves produced by compact binary systems and mergers of supermassive black holes. LISA/eLISA will observe gravitational waves by measuring differential changes in the length of its arms, as sensed by laser interferometry. Each of the LISA spacecraft contains two telescopes, two lasers and two test masses, arranged in two optical assemblies pointed at the other two spacecraft. This forms Michelson-like interferometers, each centred on one of the spacecraft, with the platinum-gold test masses defining the ends of the arms. The entire arrangement, which is ten times larger than the orbit of the Moon, will be placed in solar orbit at the same distance from the Sun as the Earth, but trailing the Earth by 20 degrees, and with the orbital planes of the 3 sciencecraft inclined relative to the ecliptic by about 0.33 degree, which results in the plane of the triangular sciencecraft formation being tilted 60 degrees from the plane of the ecliptic.〔 The mean linear distance between the constellation and the Earth will be 50 million kilometers. To eliminate non-gravitational forces such as light pressure and solar wind on the test masses, each spacecraft is constructed as a zero-drag satellite, and effectively floats around the masses, using capacitive sensing to determine their position relative to the spacecraft, and very precise thrusters to keep itself centered around them. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Evolved Laser Interferometer Space Antenna」の詳細全文を読む スポンサード リンク
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