The European Space Agency (ESA) is Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
Find out more about space activities in our 23 Member States, and understand how ESA works together with their national agencies, institutions and organisations.
Exploring our Solar System and unlocking the secrets of the Universe
Go to topicProtecting life and infrastructure on Earth and in orbit
Go to topicUsing space to benefit citizens and meet future challenges on Earth
Go to topicMaking space accessible and developing the technologies for the future
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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.