The goal of LISA Pathfinder is to test the technology for a major ESA mission planned for the near future: LISA, aimed at detecting the predicted ripples in space-time generated by very massive objects such as black holes. Since LISA requires new, challenging technical solutions, LISA Pathfinder is an essential intermediate step to reduce the technological risks LISA faces.
LISA Pathfinder, formerly known as SMART-2, was approved by the ESA Science Programme Committee (SPC) in November 2000. SMART stands for 'Small Missions for Advanced Research in Technology', a family of missions designed to test technologies identified as critical to the success of the so-called 'Cornerstone' missions. LISA Pathfinder is the second of these missions.
LISA Pathfinder and LISA: Detecting Gravitational Waves
The Laser Interferometer Space Antenna (LISA) mission consists of three spacecraft flying 5 million kilometres apart in orbits around the Sun. Their goal is to detect gravitational waves, distortions of space-time thought to be generated when a massive body is accelerated or disturbed. Although Albert Einstein already predicted the existence of these 'space-time ripples' in 1916, in his General Theory of Relativity, gravitational waves have never been detected directly. In principle it should be possible by measuring the vibrations they should cause in a solid body when passing by, which is exactly the purpose of LISA.
To achieve that goal the relative position of several solid blocks placed in different spacecraft, 5 million kilometres apart, will be constantly monitored with a high accuracy using laser-based techniques. A gravitational wave passing through the spacecraft will cause these bodies to vibrate, changing the separations between them.
But the changes will be so subtle that in order to perceive them the position of each satellite must be controlled up to the nanometre level (one nanometre is one millionth of a millimetre). Also, scientists need to be completely confident that the vibrations of the solid blocks in each spacecraft are indeed caused by a gravitational wave and not by other phenomena, such as the solar wind.
The key technologies needed to fulfill these two requirements will be tested in LISA Pathfinder. For instance, LISA Pathfinder will perform systematic tests and calibration on technologies like micro-Newton thrusters, inertial sensors (two free-floating proof masses), and a laser interferometer system for position measurement and control.
Last Update: 11 August 2008