Golden cubes for LISA

In 2015, LISA Pathfinder tested important technology for the upcoming LISA mission. Central in the technology demonstration were two cubes of solid gold-platinum alloy. Each cube is a test mass with sides of 4.6 cm and weighing 1.96 kg. One of those cubes is pictured here.

The three spacecraft of the LISA mission will each host two of these test masses. They are free-floating and contained within an ‘electrode housing’. Gravitational waves can be discovered when the distances between the cubes in different spacecraft changes. LISA will track these changes by exchanging laser beams between adjacent pair of spacecraft.

The LISA Pathfinder mission proved that the test masses can be kept in a motion where they are subject only to gravity; the test masses do not touch the spacecraft, they are floating within it. Each spacecraft has the important job of making sure that nothing, besides the geometry of spacetime itself, affects the masses, which are in free fall.