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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This schematic accompanies a new sequence of Phobos images, created as the small martian moon passed in front of ESA’s Mars Express. The images were captured at different phase angles. The phase angle (marked as ‘φ’ in the graphic) is the angle between a light source (in this case, the Sun) and the observer (Mars Express), as viewed from the target object itself (Phobos). In the movie of Phobos, the initial phase angle is 17 degrees (A), drops to almost zero degrees mid-way through (when Phobos is at its brightest, B), and then rises to 15 degrees by the end of the animation (B).