Artist's impression of ESA's LISA Pathfinder and its propulsion module after separation.
Credit: ESA

Pointing the Path for LISA

One of the most astounding implications of Einstein's General Theory of Relativity is the existence of gravitational waves. According to the General Theory, the presence of a stationary mass curves spacetime, and the acceleration of mass produces waves in this curved spacetime. Thus gravitational waves are ripples in the very fabric of spacetime itself, produced by the acceleration of massive bodies. Although gravity waves were predicted about a century ago, they have never been directly detected, though indirect indications of the existence of gravity waves radiating away from accelerating compact objects have been oberved. The spacetime ripples produced by gravity waves cause the separation between points in space to change. But because the gravity waves from even merging supermassive black holes produce only tiny deviations in spacetime (only about one-hundreth the size of an atom), detection of gravity waves is extremely challenging and require extremely high precision localization. The Laser Interferometer Space Antenna, or LISA, will use a constellation of free-falling satellites in the quiet enviroment of space to determine the tiny changes in their relative positions which would be produced by the passage of a gravity wave. A satellite experiment called LISA Pathfinder, pictured above, is the first step in testing the technologies needed by LISA. LISA Pathfinder consists of the LISA Technology Package, containing two test masses and equipment to measure deviations in positions of the masses at a level of one-billionth of a meter relative to the LISA Pathfinder spacecraft, and at a level of one-trillionth of a meter relative to each other. The second key technology being demonstrated on LISA Pathfinder is the Disturbance Reduction System, which keeps the test masses precisely in free fall by controlling the spacecraft's position to a millionth of a millimeter. LISA Pathfinder was launched from Kourou, French Guiana, at 11:04 p.m. EST on December 2, and its mission will last for six months.
Published: November 7, 2015

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Page Author: Dr. Michael F. Corcoran
Last modified Monday, 14-Dec-2015 07:43:13 EST