The huge stellar census is on track for completion next year, with astrophysicists hopeful it will help resolve mysteries about the origin and evolution of the galaxy.
The Gaia Mission aims to draw the biggest and most precise three-dimensional map to date of our galaxy, the Milky Way.
At the heart of the mission is the 10 metre-wide Gaia spacecraft.
Launched in December 2013, it contains two telescopes and three science instruments that precisely determine the location of stars and their speeds.
Data from the spacecraft have been transmitted to three ground stations.
One is located in the remote Western Australian town of New Norci.
During its first 14 months scanning the sky, Gaia has collected around 500 billion astronomic measurements, and helped identify some 400 million new stars.
Astrophysicists have been excitedly awaiting the release of a first batch of data.
The data release, like the mission, is not without obstacles.
"Good morning ladies and gentlemen. And welcome to the European Space Astronomy Centre, ESAC, here in Madrid."
A technical hitch at the start of the launch initially prevented proceedings streaming live online.
It was a hiccup the Head of Communications at ESAC, Marcus Bauer, smoothed over midway through.
"We are streaming again and I take this opportunity to apologise because if we are missing the first part we will put it online, on demand, as soon as possible so you can see that as well."
In a taste of what the final catalogue will contain, the European Space Agency released precise data on more than two million stars.
Gisella Clementini from the Astronomical Observatory of Bologna in Italy struggled to contain her delight.
"I should say that it is very difficult for me to be here now because I am so excited and I would like to be at my desk downloading Gaia data. So I will sort of rush through my presentation."
A pan-European consortium made up of about 450 scientists and software engineers has been given the painstaking task of transforming the raw information from the spacecraft into something useful.
The chairman of the Gaia Data Processing and Analysis Consortium, Anthony Brown, says the highly precise data has allowed them to catalogue the position of stars to a level of accuracy never possible before.
"To summarise the first data release that we are presenting today I think it is a major advance in the mapping of the heavens. It really represents also a very large increase in fundamental stella data. This is really unprecedented. That is why I can say this will really cause a revolution in stellar physics."
Gaia Mission Manager Fred Jansen says future data releases will add extra detail.
"We will see spectrometry - the accurate measurements of the velocities of stars. We will get the characterisation of stars in terms of temperature, things related to composition etc. We will get the individual measurements will at the end of the mission be released. And that's course that is where a lot of astronomy can be harvested from the Gaia data."
Director of Science at the European Space Agency, Alvaro Gimenez, says the mission will help astrophysicists answer big questions.
"How the universe is made, what it is made of. How it evolves. What is its origin? What is its destination? But also what are the laws of physics that underpin its behaviour?"
The full atlas of one billion stars is set to be released at the end of next 2017.
