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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Over more than 17.5 years of operation, the power provided to the Ulysses spacecraft by the Radioisotope Thermoelectric Generator (RTG) has been declining naturally. The RTG eventually became unable to provide enough heat to the craft and its payload. In mid-January 2008, the situation worsened when the main radio transmitter also failed – its warmth otherwise kept the fuel from freezing.