LISA Pathfinder is testing the key elements that could be used for a future mission to detect gravitational waves – ripples in spacetime predicted by Albert Einstein in his General Theory of Relativity. To this end, it will release two test masses into near-perfect free fall and measure their motion with unprecedented accuracy.

LISA Pathfinder was launched on 3 December 2015 and arrived today in its orbit around ‘L1’, the first libration point of the Sun-Earth system, a virtual point in space some 1.5 million km from Earth towards the Sun. LISA Pathfinder’s arrival came after a final thruster burn using the spacecraft’s hard-working propulsion module on 20 January.

The small, 64-second firing was designed to slightly change its speed and just barely tip the craft onto its new orbit about L1.