August 26, 2013
Thirteen years after its approval, the Gaia telescope is finally scheduled to be launched by the European Space Agency (ESA) into Earth's orbit in less than three months. Its mission consists of mapping about a billion stars, discovering thousands of exoplanets as well as dwarf planets at the edge of the solar system.
Artist's concept of the Gaia spacecraft.
On November 20, 08:57 GMT, the European Space Agency will launch a Soyuz rocket carring Global Astrometric Interferometer for Astrophysics (GAIA) spacecraft with its two telescopes. The rocket will launch from the Guiana Space Centre in French Guiana.
Its mission? During the next five years it will observe about one billion stars in the Milky Way in order to create a three-dimensional map and study the origin and evolution of our galaxy. It will also look for exoplanets, mostly gas giants, as well as objects in our solar system such as asteroids between Earth and the Sun or icy dwarf planets at on the outer frontier of the solar system. Finally, it will test Einstein's theory of general relativity by observing how the Sun's gravitational pull bends starlight.
"The estimate of the number of stars in the Milky Way is between 100 and 200 billion stars, so we observe between one-half and one percent of these stars," said Timo Prusti, scientist at Gaia's project. "Because of the completeness of Gaia to a limiting magnitude, this proving of 1 percent of these objects will help us reconstruct the remaining part. We’re not going to take a full census of the Milky Way, but we are going to look at a billion stars and we’ll have enough statistical power to deduce the structure of the Milky Way."
The mission was approved by ESA in 2000. It costs 740 million euros and is expected to collect a petabyte of data. The telescope will orbit the Earth at 1.5 million kilometers from the planet, at L2 Lagrangian point, where it will maintain the same relative position in respect to the Sun and Earth.
The spacecraft was produced in Toulouse, France by an industrial team led by Astrium Satellites and delivered by Antonov An-124 transport airplane to French Guiana on August 23. "The most exciting moment is the work toward the launch itself, and the fact that it’s shipped to Kourou [French Guiana] makes it very real," Prusti said.
This was the first of two shipments. The second shipment, due on August 28, will deliver the sunshield which will keep Gaia's telescopes and instruments in the shadow during the mission in order to control the temperature inside, keeping it at minus 110 degrees Celsius.
"This is the start of the launch campaign," said Giuseppe Sarri, Gaia's project manager. "In the first month, we will do plenty of checks on the spacecraft. Once we have the spacecraft in the clean room, we will do inspections, and we will do some basic functional testing to check that everything is still fully functional after the transport. Then we will integrate the sunshield on the spacecraft."
Sunshield has the diameter of 10 meters, folded against the body of the spacecraft during the launch. Its deployment will be tested, as Sarri said, in the clean room during the next month.
"This is the first big chunk of activity, which takes place in one dedicated clean room in French Guiana," Sarri said. "Then we move the spacecraft to another place called the hazardous payload facility because we need to fuel the spacecraft and put the propellant in the tanks."
Gaia will launch with about 296 kg of fuel, most of which will be consumed during the first 30 days of the launch. Once its at the L2 Lagrangian point, the remaining fuel will be used for Gaia's cold gas micro-propulsion system. This will keep the craft in a stable spin of four rotations per day.
"When [fueling] is done, we go to another place where we integrate the spacecraft on the adapter, which is an interface cone to adapt the spacecraft to the launcher," Sarri said. "Then we integrate the spacecraft, plus the adapter, on the Fregat, which is the fourth stage of the launcher. Then we close the composite with the two fairing halves and we have the upper part of the rocket ready. At that point in time we go to the launch pad, and there we will integrate this upper composite cylinder on top of the Soyuz three-stage rocket."
If you're excited by Gaia's mission, make sure to stay tuned for more news in months to come.