ESA Gaia: Largest Space Camera is ready to map a billion stars

Now whizzing through space, 1.5 million km from Earth. 

Credit: ESA-CNES-Arianespace / Optique Vidéo du CSG - G. Barbaste

After its successful launch in December, European Space Agency's (ESA) Gaia has now taken up its position in space and is ready to survey the skies.

With the help of two onboard telescopes focused onto the largest ever space camera, Gaia is estimated to catalogue nearly one billion stars in its 5-year mission.

Like Hipparcos before it, ESA's Gaia will map stars in the Milky Way. It will do this by measuring the brightest billion objects and determine their three-dimensional distribution and velocities.

It also has the ability to measure the temperature, mass, and chemical composition of these billion objects.

Gaia will be able to discern objects up to 400,000 times dimmer than those visible to the naked eye.

The positional accuracy of its measurements are akin to measuring the width of a human hair at a distance of 500 km.

The process will involve scanning each part of the sky an average of 70 times over its five-year mission lifetime.

This means scanning the entire sky twice every 63 days, once through each of the two telescopes, making it a powerful tool for spotting time-evolving phenomena such as binary systems, supernovae, and exoplanets.

Compared to ESA's Hipparcos Space Telescope, ESA's Gaia will be able to measure 500 times the number of stars, extending to objects 1000 times dimmer than the dimmest that Hipparcos could catalogue.

Test image from Gaia: Slightly shaky to start with, but it’ll get there. Credit: ESA/DPAC/Airbus DS

The technology that makes this possible is the largest camera ever launched into space – 940 million pixels.

That is why a lot of effort before launch was on figuring out exactly how to get the huge amount of data Gaia will produce back down to Earth.

When a picture is taken a number of charged-coupled devices (CCDs), the stuff most digital camera sensors are made off, are dedicated to spotting objects before they fall onto the main focal plane.

This allows the instrument to track the objects as they pass and only retain small regions around the object, reducing the file-size needed to be sent to Earth.

In five years it will send only 100 TB of data (1 TB is 1000 GB).

Once the data arrives to Earth, there is a system in place to analyse the data and distribute alerts to ground-based observatories if anything quickly evolving and potentially interesting is spotted, such as supernovae.

The catalogue produced by Gaia is expected to contribute to many areas of astrophysics;

• multiply our database of exotic objects such as' 
• exoplanets, 
• white and brown dwarfs, and 
• supernovae many-fold, contribute to more precise measurements of General Relativity, 
• help to constrain the measurements of the presence and location of dark matter, and 
• give us more accurate information about our galactic neighbourhood and its evolution.