Worlds Largest Camera

Over the last few decades we’ve seen a variety of large and amazing telescopes. From the Hubble Space Telescope to the Herschel Space Observatory, we’ve been able to observe our Solar System, the Milky Way and even the universe in unprecedented detail.

Now, the ESA wants to attempt something new. Using the revolutionary Gaia spacecraft, it will track the motion and position of 1% of the 100 billion stars in our own galaxy. It’s a daunting prospect but one that could provide us with a fresh new insight into the formation and structure of the Milky Way, and also glean new information about asteroids, exoplanets and our Solar System.

The Gaia spacecraft will fly the largest camera ever with a total of about 1,000 million pixels. This revolutionary piece of equipment will be performing wide-angle astrometry – the science of determining the position of objects in the sky – to complete its five-year mission. Until now, astrometry has largely been confined to Earth, and it has been difficult. The Sun and the Moon are both a nuisance for Earth-based astrometry, which is what makes Gaia so important.

Gaia spacecraftThis spacecraft won’t be placed in orbit around Earth, but flown out to the Sun-Earth Lagrange Point 2, a position 1.5 million kilometres (930,000 miles) away in line with the Earth and Sun that provides a shielded view of the entire cosmos. “All the ‘bad things’, the Sun, the Earth and the Moon, are roughly in the same direction,” says Gaia Project Scientist Timo Prusti. “So if you shield that ‘bad’ direction, then you are free to look the other side.”

The L2 position will enable Gaia to use its incredible camera to make the largest and most precise three-dimension map of our galaxy. Every star it observes will be accurately measured to determine its motion around the centre of the galaxy. Most stars gained their motion from the birth of the Milky Way so, by studying this, Gaia will enable astronomers to peer back in the history of the galaxy. Gaia will observe each of its one billion stars about 100 times.

Gaia is also expected to make other discoveries. It “will also address questions concerning our own Solar System, extra galactic objects (some half a million quasars will be observed and several million galaxies), stellar astrophysics (by providing the distances to objects) and general relativity,” explains Prusti. Gaia will also “provide several thousand new planets, but the strength is in the area of Jupiter-like planets in five to ten year periods around their stars.”

Gaia's cameraThe spacecraft itself is composed of three main components totaling about two tons in launch mass. The first is the payload module, which provides support and electronics for the camera and also processes the raw data. The mechanical service module houses mechanical, structural and thermal elements that support the camera and the spacecraft’s electronics. Finally the electrical service module manages the data and provides communication with Earth, amongst other tasks.

Gaia’s camera isn’t like a traditional camera, though. “Gaia will provide roughly the same spatial precision as Hubble, but for the whole sky,” explains Prusti. “However, Gaia is only doing point sources. So you will not get the pretty pictures Hubble is providing. Gaia provides an all sky map with high precision positions and movements of objects”

Gaia is expected to launch in August 2013 atop a Soyuz rocket. While its initial mission will last until 2018, it could be extended. “Hardware and propellant is scoped nominally for a one year extension,” says Prusti, “and clearly if everything works it is no problem to find a science case to support applications for further extensions.” However long it lasts, you can be sure that Gaia’s mission will provide some groundbreaking scientific discoveries that will increase our understanding of the Milky Way and its resident objects.