Airbus Defence and Space

From Hipparcos to Gaia

In Kourou, Airbus Defence and Space is putting the finishing touches to the Gaia satellite, ESA’s second global astrometry mission after Hipparcos.

Gaia will take off from French Guiana in a few weeks, headed for one of the five Lagrange points orbiting the sun at 1.5 million kilometres from Earth. It will then assume its role as the keenest ‘eye’ to have ever contemplated the Milky Way.

“In astrometric terms, Gaia will have a precision 100 to 1,000 times greater than its predecessor Hipparcos,” explains Vincent Poinsignon, head of Gaia’s design and manufacture at Airbus Defence and Space.

When ESA launched Hipparcos – also primed by Airbus Defence and Space – in August 1989, it was the first satellite devoted to astrometry, a branch of astronomy involving measurement of the position and movement of celestial bodies as well as their distance from Earth. Up until its retirement in 1993, it amassed a catalogue of 120,000 stars with a precision 200 times greater than any previous measurements.

Now, Gaia’s high-end technology will make Hipparcos seem as primitive as a pair of binoculars. Once in orbit around the sun, Gaia will begin to measure with extreme precision the characteristics of a billion stars, and this data will then be used to generate a 3D chart of our galaxy. Its telescopes will have each star in their sights around 70 times over a five-year period, making a total of 40 million observations per day. The data recorded on each of these stars will include their speed, magnitude, position and distance from Earth.

While Hipparcos could measure the diameter of a human hair at a distance of 20 kilometres, Gaia will be capable of the same feat at a distance of 1,000 kilometres. This sensitivity will enable it to detect more than 250,000 objects in our solar system (mostly asteroids), 15,000 extrasolar planets, 50,000 brown dwarfs and approximately 20,000 supernovae.

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