• Scheduled for launch 2009
• A joint mission between the European Space Agency and NASA

Gravitational waves are ripples in space and time. They were predicted by Einstein’s 1916 Theory of General Relativity and are thought to be generated by some of the most violent astrophysical events - such as exploding stars and collisions of black holes at the centres of galaxies.

But first LISA Pathfinder must prove that a test mass can float freely in space so that any effects on its trajectory can only be the result of external gravitational forces. These test masses are two metal cubes which will be placed into gravitational freefall.

For more information, visit the ESA and NASA websites.

Mission facts

• The LTP (LISA Technology Package) and DRS (Disturbance Reduction System) are housed in the spacecraft.
  
  
• LISA Pathfinder will be launched into a temporary parking orbit before shifting into successively larger orbits until reaching its destination 1.5 million km from Earth. This is the L1 Lagrange point where the gravitational effects of the Sun and the Earth cancel each other out.
  
  
• On LISA Pathfinder, the test masses will be 35 cm apart. On the LISA mission, scheduled for 2018, that distance will be five million kilometres.
  
  
• ESTEC (European Space Research and Technology Centre) in Noordwijk, the Netherlands, will co-ordinate the science and technology operations.

Technology

The two test masses are 46 mm cubes made of a gold and platinum alloy, suspended in a vacuum can that contains a readout system to monitor the cube’s position within its housing.

Europe developed the Field Emission Electric Propulsion (FEEP) system - one of LISA Pathfinder’s two micro-propulsion systems.

UK involvement

UK scientists from the University of Birmingham, the University of Glasgow and Imperial College London are collaborating on LISA Pathfinder.

Astrium Limited is the spacecraft’s main contractor and is testing the prototype Science Module before integration of flight equipment. SciSys Limited is the software architect.