LISA
Full Name: Laser Interferometer Space Antenna
Phase: Under study
Mission Project Home Page: http://lisa.jpl.nasa.gov/
Program(s): Physics of the Cosmos
Unlike electromagnetic radiation (radio to optical to gamma rays), gravitational waves penetrate through all matter, thereby allowing us to see back to the beginning of the Universe without obscuration by dust or other matter. LISA, the first instrument to directly measure gravitational radiation from space, will peer back to the epoch of initial star formation. It will test Einstein’s theory of general relativity in the strong-field regime, and will witness the merger of supermassive black holes throughout the Universe, along with other astrophysical phenomena.
LISA is a gravity wave telescope similar to a Michelson interferometer. Three identical spacecraft are flown in deep space in an Earth-trailing orbit, forming the vertices of an equilateral triangle with arm spacing of five million kilometers. Laser beams between these spacecraft enable interferometric measurement of relative displacements between these spacecraft, with the incredible accuracy of several picometers. With this accuracy, one is able to measure the tiny distortions of spacetime caused by a passing gravitational wave. These waves, produced by such cataclysmic events as the merger of supermassive black holes, propagate unattenuated throughout the Universe, and thus allow us to see back to the time of star formation and beyond.
LISA detects gravitational radiation with periods of several seconds to a few hours, such as that produced by two coalescing massive black holes in a distant galaxy. LISA will also provide an unprecedented test of strong field general relativity theory. As the first dedicated space-based gravitational wave observatory, LISA will detect waves generated by binaries within our Galaxy, the Milky Way, and by massive black holes in distant galaxies. LISA will make its observations in a low-frequency band that ground-based detectors can't achieve. The difference in frequency bands between LISA and gravity-wave ground detectors such as the Laser Interferometer Gravitational Wave Observatory (LIGO), which operate above 1 Hz, make these detectors complementary rather than competitive.