After a 10-year chase taking it billions of miles across the solar system, the European Space Agency’s (ESA) Rosetta spacecraft made history on Wednesday, 6 August, when it became the first probe to rendezvous with a comet on its journey around the sun. Rosetta fired its thrusters on its final approach to Comet 67P/Churyumov-Gerasimenko, known as ‘Chury’ for short, on Wednesday morning. Half an hour after the burn, scientists announced that the craft had entered into the orbit of the streaking comet.
"After 10 years, five months and four days travelling towards our destination, looping around the sun five times, we are delighted to announce finally 'we are here'," said Jean-Jacques Dordain, ESA's Director General, in a statement.
Rosetta is now the first spacecraft in history to rendezvous with a comet, a major highlight in exploring human origins. Previous missions have performed comet fly-bys but Rosetta is different. This probe will follow the comet for more than a year, mapping and measuring how it changes as it is blasted by the sun's energy.
Chury and Rosetta now lie some 400 million kilometers from Earth, about half way between the orbits of Jupiter and Mars. The mission has now achieved the first of what it hopes will be a series of historic accomplishments. In November mission controllers aim to place the robotic lander Philae on the surface -- something that has never been done before.
The first spectacular and detailed images taken from just 130km away show boulders, craters and steep cliffs and are already causing excitement. "The pictures coming back so far look intriguing -- and imagine the kind of scenes we can expect when Philae lands this coming November," said Dr. Robert Massey of the Royal Astronomical Society in the UK.
To get to its destination the spacecraft has covered nearly five billion kilometers and as the comet hurtles towards the sun it will reach a speed of about 100,000 kilometers per hour. Mission controllers had to use the gravity of Earth and Mars to give the probe a slingshot acceleration to meet its target on the right trajectory. Rosetta also had to be put into hibernation for more than two years to conserve power before being woken up successfully in January this year.
For the next few weeks, ESA says the spacecraft will be in a triangular orbit until it gets to about 30km of the surface when it will start its close observations. Scientists hope to learn more about the composition of comets and perhaps whether they brought water to the Earth or even the chemicals that make up the building blocks of life. "It really is such a step forward to anything that has come before," said project scientist Matt Taylor.
Rosetta will soon begin mapping the surface of and finding out more about its gravitational pull. This will help to find a suitable landing site for Philae and allow engineers to keep Rosetta in the right orbit.
As comets approach the sun, any ice melts and is turned into an ionized gas tail. The dust produces a separate, curving tail. It's these processes that Rosetta scientists hope to be able to study from close proximity.
Chury is known as a short-period comet. It reappears every six years as its orbit brings it close to the sun. Halley's Comet has a period of about 76 years and is not due to return close enough to Earth to be visible until 2061. Others only return after thousands of years. While it is unlikely that you will be able to see comet 67P with the naked eye, you can follow the progress of the mission on http://blogs.esa.int/rosetta.