Science Article

The European Space Agency is continuing to prepare for the launch of its Gaia spacecraft set for 2013. Gaia's mission will see it creating a 3D map of a billion stars in the Milky Way using a 1.5-gigapixel camera.

In this photo, taken at the EADS CASA test facility in Madrid, Spain, checks are being made on Gaia's 1.5-metre-wide antenna panel to ensure data will reach Earth safely. The foam spikes on the walls of the test room block radio signals to simulate space. Electronic steering will ensure the antenna is always directed towards its target while the spacecraft rotates in space as it maps the stars, asteroids, extrasolar planets and other objects.

After launch, Gaia will take up an orbit around the sun 1.5 million kilometres beyond, but in pace with, Earth's to minimise the distance the weak signal has to travel. During its initial five-year mission, Gaia will send an estimated 200 terabytes of data to radio dishes in Spain and Australia. A working antenna is obviously central to downloading this data safely.

What's special?

Gaia will rely on the proven principles of ESA’s Hipparcos mission to create an extraordinarily precise three-dimensional map of more than a thousand million stars throughout our Galaxy and beyond. Gaia will also map the motions of stars, which encode their origins and evolution. Gaia will provide the detailed physical properties of each star observed, revealing luminosity, temperature, gravity and composition. This huge stellar census will provide the basic observational data to tackle an enormous range of important problems related to the origin, structure and evolutionary history of our Galaxy.

Gaia will achieve its goals by repeatedly measuring the positions of all objects down to magnitude 20 (about 400 000 times fainter than can be seen with the naked eye). Onboard object detection will ensure that variable stars, supernovae, other transient celestial events and minor planets will all be detected and catalogued to this faint limit. For all objects brighter than magnitude 15 (4000 times fainter than the naked eye limit), Gaia will measure their positions to an accuracy of 24 microarcseconds. This is comparable to measuring the diameter of a human hair at a distance of 1000 km. It will allow the nearest stars to have their distances measured to the extraordinary accuracy of 0.001%. Even stars near the Galactic centre, some 30 000 light-years away, will have their distances measured to within an accuracy of 20%.

Journey

Gaia will map the stars from an orbit around the Sun, at a distance of 1.5 million km beyond Earth’s orbit. This special location, known as the L2 Lagrangian point, keeps pace with Earth as we orbit the Sun.

L2 offers a stable thermal environment, a clear view of the Universe because the Sun, Earth and Moon are always outside the instruments’ fields of view, and a moderate radiation environment. An operational lifetime of five years is planned.
 

Site reference : http://www.esa.int/, http://www.newscientist.com/