The remarkable achievement of the European Space Agency’s Rosetta spacecraft and its Philae lander, touching down on a comet last week, is the latest in a long history of deep space missions by the ESA.
On this side of the Atlantic we tend to hear mostly about the accomplishments of NASA, the Russian Space Agency and, occasionally, the Canadian Space Agency; but the Europeans have been exploring space independently for decades, with remarkable accomplishments that go almost unrecognized here.
Established more than 40 years ago, the ESA is a consortium of 20 European countries that have banded together in a cooperative effort to explore space.
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They have their own astronauts, space laboratories - including one of the modules of the International Space Station - orbiting telescopes, robot probes to the planets and fleet of rockets flown from a spaceport in French Guiana.
One of those rockets, the Ariane 5, is one of the largest in the world, and, together with other rockets in the fleet, has launched half of the Earth’s commercial satellites.
When it comes to catching comets, the Europeans were the first to do it, with a mission called Giotto that flew past the famous comet Halley in 1986. That mission provided us with the first image of a comet nucleus, and closeups of the gas jets that are the source of the long cometary tails which have graced our skies throughout history.
In 2005, the Europeans made history again by hitching a ride on the American Cassini mission to Saturn. Their probe, named Huygens, looked like a flying saucer attached to the side of Cassini, which is exactly what is was. Its disc shape allowed it to explore one of Saturn’s moons, Titan - the only moon in the solar system with a thick atmosphere, one actually denser than the Earth’s.
Huygens plunged into Titan’s atmosphere, then opened parachutes and floated all the way to the surface. During the two-and-a-half hour descent, instruments on board measured the contents of an organic, brown, high-altitude haze that covers the entire moon.
That haze is made of chemicals believed to have existed on the early Earth before life began. Beneath the haze layer, the skies opened up to reveal a bizarre, icy landscape - carved by rivers of liquid methane and ethane, which flow like water on this super-cold world.
Then, finally, at touchdown, we saw for the first time a truly alien landscape on the surface of another planet’s moon.
So, it was totally appropriate that the Europeans made the first-ever landing on a comet.
Even the journey to comet 67P Churyumov-Gerasimenko by the Rosetta spacecraft was an astounding feat of navigation.
Launched 10 years ago, the probe had to circle the sun several times, returning to Earth three times to get a gravity assist from our planet’s motion through space. Then, it got another one from Mars, to gain enough momentum to match the speed of the comet. Rosetta’s flight path resembles the spinning windup of a discus thrower, or caber tosser in Highland Games; except that once tossed, the spacecraft took a decade to reach its target.
That speeding target, by the way, is only about five kilometres across, which means it would easily fit within the boundaries of an average city. Considering the billions of kilometres Rosetta had to cover just to get there, the comet is a microscopic target. And they hit the bull’s eye.
Even though the Philae lander bounced on touchdown and ended up in a shadow, unable to recharge its batteries, the scientists were still able to accomplish more than 80 per cent of their objectives. And there is still the possibility that, later in the comet’s flight around the sun, the shadow might move, and the probe may come to life again.
Meanwhile, the Rosetta mothership is in fine shape and will continue to follow the comet as it becomes more active on its journey around the sun during the next year.
So, keep your eye on the Rosetta mission; there is much more to come. And give a salute to the European Space Agency and its remarkable accomplishments.