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
Go to topicThank you for liking
You have already liked this page, you can only like it once!
11/11/24: Click here for up-to-date information on the Atomic Clock Ensemble in Space.
Schematic of ACES containing PHARAO and Space H-Maser.
An atomic clock in space will allow a new kind of Earth research: relativistic geodesy. A radio signal from the surface of a planet climbs 'uphill' through the gravitational field (out of a gravity well), so when it is received by an observer in a weaker gravitational field its wavelength is
seen to be longer, as predicted by Einstein's theory of relativity. Measuring this change in wavelength can be used to map the gravity of our planet. These measurements require a timekeeper of almost unimaginable accuracy – such as
ACES.