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Abstract

More than 80 years ago, Einstein has predicted that accelerated masses will emit gravitational waves, propagating distortions of the spacetime fabric. The gravitational wave spectrum of known and expected sources covers many decades in frequency. While sources in the audio-frequency regime above 1 Hz are accessible to ground-based detectors, sources in the low-frequency regime can only be observed from space because of the unshieldable background of Newtonian gravitational noise. LISA is a laser-interferometric gravitational wave detector in space designed to observe gravitational wave signals from galactic as well as cosmological sources in the frequency range from 0.1 mHz to 1 Hz. LISA comprises a cluster of three spacecraft at the corners of an equilateral triangle of 5 Mio km size. The cluster is in an earth-like heliocentric orbit trailing the earth by 20 degrees. Each spacecraft carries lasers and free-flying proof masses and is kept on a purely inertial orbit by drag-free technology using field emission electric propulsion