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!
Disguised in a crowded field of stars, the tiny white dot highlighted in these two images is none other than ESA’s Gaia satellite as seen with the Very Large Telescope Survey Telescope at the European Southern Observatory in Chile.
Gaia was launched on 19 December 2013 from ESA’s Spaceport in French Guiana, and is now 1.5 million km away, orbiting a virtual point in space known as L2. From this vantage point, Gaia will scan the sky continuously for the next five years, charting a billion stars in the Milky Way.
Gaia’s survey will yield an unprecedented 3D map of stellar positions and motions to investigate the origin and evolution of the Galaxy. Astronomers need Gaia to pinpoint stars to an extraordinary accuracy – for the brightest stars the goal is to measure their position in space to an accuracy equivalent to the size of a euro coin on the Moon as seen from Earth. But to meet such an ambitious requirement, they must know the position of Gaia in the Solar System, too.
Fortunately, it is possible – if not easy – to observe Gaia using ground-based telescopes, since small imperfections in the sunshield, and structures like the solar panels and antenna reflect diffuse light. So far away, Gaia is about a million times fainter than is detectable by the naked eye.
To measure Gaia’s position in the sky, a network of small and medium telescopes are monitoring the spacecraft on a daily basis. This information is being fed into the orbit reconstruction being performed at ESA’s Space Operations Centre, yielding an accuracy of 150 m on Gaia’s position and of 2.5 mm/s on its motion.
These two images, taken about 6.5 minutes apart on 23 January, are the result of a close collaboration between ESA and the European Southern Observatory to observe Gaia.