Europe's Rosetta probe yesterday became the first human spacecraft in history to manoeuvre alongside a speeding comet.
The spacecraft fired its thrusters for six and a half minutes to finally catch up with comet 67P/Churyumov-Gerasimenko.
"We're at the comet!" said Sylvain Lodiot of the European Space Agency (Esa) operations centre in Darmstadt, western Germany.
"After 10 years, five months and four days travelling towards our destination, looping around the Sun five times and clocking up 6.4 billion km (4 billion miles), we are delighted to announce finally 'we are here'," said Jean-Jacques Dordain, director general of Esa.
Launched on board an Ariane rocket in March 2004, Rosetta has taken a long route around our Solar System to catch up with comet 67P.
In a series of fly-pasts, the probe used the gravity of the Earth and Mars to increase its speed during the 6 billion km chase.
To save energy, controllers at the European Space Agency's centre in Darmstadt, Germany put Rosetta into hibernation for 31 months.
In November, in what will be another first, Rosetta will land a robot, Philae, onto the surface of the comet. It carries nine experiments, including a drill to sample beneath the surface. The lander is named after Philae island in the Nile, where an obelisk was found that was used along with the Rosetta Stone to decipher Egyptian hieroglyphics.
Europe's Rosetta probe goes into orbit around distant comet
BBC News
6 August 2014
Philae robot's task in November: No mission has ever attempted to make a soft landing on a comet before
Europe's Rosetta probe has arrived at a comet after a 10-year chase.
In a first for space history, the spacecraft was manoeuvred alongside a speeding comet to begin mapping its surface in detail.
The spacecraft fired its thrusters for six and a half minutes to finally catch up with comet 67P/Churyumov-Gerasimenko.
"We're at the comet!" said Sylvain Lodiot of the European Space Agency (Esa) operations centre in Germany.
"After 10 years, five months and four days travelling towards our destination, looping around the Sun five times and clocking up 6.4 billion km (4 billion miles), we are delighted to announce finally 'we are here'," said Jean-Jacques Dordain, director general of Esa.
Launched on board an Ariane rocket in March 2004, Rosetta has taken a long route around our Solar System to catch up with comet 67P.
In a series of fly-pasts, the probe used the gravity of the Earth and Mars to increase its speed during the 6 billion km chase.
To save energy, controllers at the European Space Agency's centre in Darmstadt, Germany put Rosetta into hibernation for 31 months.
In January
they successfully woke the craft from its slumber as it began the final leg of the daring encounter.
For the past two months Rosetta has been carrying out a series of manoeuvres to slow the probe down.
The comet is travelling at 55,000km per hour (34,175 mph). The spacecraft's speed has been adjusted so that in relative terms it will be flying beside the comet at a slow walking pace of 1m/sec (2.2mph, 3.6kph).
At around 550m km (342m miles) distance from the Earth, messages are taking over 22 minutes to get to Rosetta.
The distances involved are so great that the complex final command sequence for Wednesday's crucial thruster burn had to be issued on Monday night.
Project scientist, Dr Matt Taylor, said: "For me this is the sexiest, most fantastic mission there's ever been. It's ticking a number of boxes in terms of fascination, exploration, technology and science - predominantly science."
Rosetta key facts
Total cost of the mission is said to be 1.3bn euros (£1.03)
The probe weighed in at 3,000kg at liftoff back in 2004, with over half of that made up of propellant
It has two 14m long solar panels to provide electrical power
The orbiter carries 11 experiments
The lander, Philae, carries nine experiments including a drill to sample beneath the surface. It was constructed by nine Esa members including Britain. Britain helped to develop Ptolemy, an instrument onboard Philae used to measure stable isotopic ratios of key volatiles on the comet's nucleus; the blankets that keep the lander warm throughout its mission; and the momentum wheel for the lander which stabilises the module during the descent and landing phases
Rosetta will have to continue to fire its thrusters every few days to maintain a triangular orbit at 100km above the rotating rock.
The craft will then travel alongside the comet for the next 15 months, studying it with a range of instruments.
Rosetta has been taking increasingly detailed photographs of 67P as it gets closer. The mysterious comet has been dubbed the "rubber duck", as some images seem to show the familiar shape as it twirls in space.
Harpooning a comet
As it moves towards the Sun, 67P will warm up and its trailing halo of gas and dust - known as the coma - will increase, offering the orbiter the chance to do some detailed scientific work.
The mission gets even more ambitious in November when, after moving Rosetta closer to 67P, mission controllers will attempt to put the Philae lander on the surface.
The lander will use harpoons to anchor itself and will carry out a series of experiments, including drilling into the material that makes up the comet.
The mission aims to add to knowledge of comets and their role in ferrying the building blocks of life around the early Solar System.
Already Rosetta has learned some intriguing details about 67P.
Using the visible, infrared and thermal imaging spectrometer, VIRTIS, Rosetta recorded temperatures on the icy object around -70C, about 20 degrees warmer than expected.
"This result is very interesting, since it gives us the first clues on the composition and physical properties of the comet's surface," said principal investigator of the VIRTIS instrument, Dr Fabrizio Capaccioni from INAF-IAPS, Rome, Italy.
BBC News - Europe's Rosetta probe goes into orbit around distant comet
