Case study

LISA Pathfinder

The LISA Pathfinder spacecraft will test technologies that could be used for a future gravitational wave observatory mission.

LISA Pathfinder spacecraft.
Artist's impression of LISA Pathfinder spacecraft. Credit: ESA.

Overview

LISA Pathfinder will test the technology needed to develop future space-borne gravitational wave detectors. Finding low-frequency gravitational waves would provide a new way of observing the Universe - one which for large-scale events billions of light-years away, would be better than observations in the electromagnetic spectrum. Mission overview:

  • all UK flight hardware is now delivered and at project level the technical issues with the caging mechanism and electrode housing have been resolved
  • scheduled for launch mid 2015
  • joint mission between the European Space Agency and NASA

Gravitational waves are ripples in space and time, they were predicted by Albert 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.

LISA Pathfinder cannot in itself detect gravitational waves – since the impact of gravitational waves is so tiny, the test masses would need to be millions of kilometres apart rather than the 38 cm available on board LISA Pathfinder. LISA Pathfinder must prove the ultra-high precision technology needed to make a test mass float freely in space. This will mean 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 detailed 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 using its powerful propulsion module until reaching its destination 1.5 million km from Earth. The propulsion module will then be released to ensure that the remaining fuel on board does not disturb the sensitive scientific instruments.

On LISA Pathfinder, the test masses will be 35 cm apart. On the LISA mission, which is not scheduled to fly until after 2020, the equivalent 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

LISA Pathfinder requires some of the most precise and advanced technology ever launched into space.

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. These thrusters produce tiny but precise amounts of force. Twenty thousand would be needed to lift one sheet of paper.

UK involvement

The UK’s involvement in LISA Pathfinder is funded by the UK Space Agency.

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

Aibus Defence and Space is the spacecraft’s main contractor and is currently testing the prototype Science Module before integration of flight equipment.

SciSys UK Ltd develops the satellites’ on-board software. LISA Pathfinder is the first ESA science spacecraft led from the UK since Giotto.

Published 28 April 2014