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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The Sun and Moon attraction also acts on satellites. The Earth's equator (and hence also the orbits of geostationary satellites) is inclined by 23 degrees with respect to the orbital plane of the Earth. Therefore, the gravity of the Sun changes the orbital plane of geostationary satellites. Together with the attraction of the Moon and the effect of the Earth oblateness, this causes the inclination to oscillate between 0 and 15 deg within 54 years. During this time the inclination vector, which is perpendicular on the orbit plane and shown in green here, draws a complete circle.