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Rendezvous in the asteroid belt

Rosetta, the space probe of the European Space Agency (ESA), has more than fulfilled its mission in the Lutetia asteroid, located between Mars and Jupiter. This was not its final destination, but a stopover on his way to the comet 67P/Churyumov/Gerasimenko, which it is scheduled to come into contact with in May, 2014. The Rosetta represents one of the most ambitious science missions of the ESA.

ALICIA RIVERA | JULY 23, 2010


Closest approach to asteroid Lutetia (ESA)

A European space probe recently flew past the Lutetia asteroid in a maneuver planned and executed with a high degree of precision. The probe caught up with the asteroid between Mars and Jupiter, at a point located 25 light-minutes from Earth, i.e. the distance that light travels in 25 minutes at a constant speed of 300,000 miles per second, or more than three times the distance between Earth and the Sun. The protagonist of the meeting was the Rosetta spacecraft, a probe of the European Space Agency (ESA), which was launched in 2004 and is on a very complex,
ambitious and long mission to reach a comet. No spacecraft has ever orbited the nucleus of a comet, as this ship will try to do, and none has descended to the surface of the comet, a feat which the Philae lander will attempt. This is one of those scientific missions that Europe has shown it excels at. Its total cost amounts to one billion euros.
Rosetta will reach its destination in four years. On route, the ship takes has taken advantage of the opportunities for exploration, and Lutetia, one of the largest bodies in the asteroid belt was sufficiently unknown to attract the attention of scientists.
“I think this is a very old object. Tonight we saw a remnant of the origin of the solar system,” Holger Sierks, one of Rosetta’s scientists, said when they received the first images of Lutetia. The flyby maneuver has not only been a satisfaction to the scientists who have obtained information about this asteroid (the analysis of the data will still take some time to complete), its composition, mass and surface properties, but at the same time it has also been a triumph for the specialists who scheduled the flyby that required such a high degree of precision.
So far the scientists know that Lutetia measures 134 meters in diameter and has a heavily cratered surface, hard hit by impacts received throughout its history, which dates back to 4,500 million years ago, making it old as the solar system.

High accuracy
Rosetta passed by Lutetia at a speed of 15 kilometers per second, getting as close as 3,162 km. But the cameras were taking pictures before and after that time. “The precision of a watchmaker [in implementing the overflight] is a great tribute to the scientists and engineers from our members and our industry and the ESA itself,” said David Southwood, scientific director of the European agency.
The mission control center in charge of operations is in Germany ESA (ESOC), while the ESA in Madrid (ESAC) is in charge of the science operations.
The final destination of Rosetta is the comet 67P/Churyumov/GerasimenkoRosetta, which has traveled 5,000 million kilometers (2/3s of its journey), is now heading towards the comet 67P/Churyumov/Gerasimenko, its final destination. When it arrives in 2014, if all goes well, it will orbit the comet nucleus and accompany it for a year on its journey towards the Sun and during six months as it distances itself from our star. It will also launch the Philae lander module that will attach itself to the comet’s frozen surface and then conduct measurements with nine scientific instruments.
The planned maneuver is a complete space odyssey. So far, besides the Moon, Mars and Venus, Earth has only landed an device on one other object in the solar system and it was also of European making. The probe was Huigens, which traveled to Saturn in NASA’s Cassini spacecraft in 2005 and descended to the floor of the moon Titan, leaving the international space community amazed at the resounding success at the complex ESA operation.
Rosetta is on track to a similar victory. It is one of those long, costly and complicated missions loaded with scientific instruments (the ship holds eleven, two of them developed by NASA), which in recent years have been relegated to the backburners by agencies eager to do more compact missions and develop faster methods for planetary exploration.

Orbital Redesign
The actual beginning of the journey to the comet was a nightmare for the ESA. In such a mission the spacecraft does not follow a direct path (which would require an extremely powerful rocket), rather it passes by one or more planets to pick up a gravitational slingshot boost. The Rosetta’s complex orbital design was commissioned by the ESA to Spanish engineer Miguel Belló-Mora.
It must be taken into account the position of Earth at the time of release, the target object and the bodies of the Solar System to be used to gather momentum when tracing the route of such a mission. The initial target for the Rosetta was the Wirtanen comet and was scheduled to arrive in 2011. The journey was strictly measured from the launch, expected in January 2003. But shortly before its scheduled launch, the Ariane rocket failed and the ESA considered it prudent to postpone the departure of one of its more ambitious missions. The delay disabled the design path and the destination of the Wirtanen comet was lost.
The solution was to find another comet that interested scientists and that was within range of orbital conditions. Belló-Mora was called to redraw the route of Rosetta with a future release and found several potential comets, among which the scientists chose 67P/Churyumov/Gerasimenko. At last the ship departed in March 2004 and has since made three gravity maneuvers with the Earth and Mars to gain momentum. In 2008, the asteroid flew by the Stein asteroid. Now, once passed Lutetia, there are no more “pit stops” to be made: the ship is now going directly to its rendezvous with the comet in May, 2014.
A THREE TON SHIP
The Rosetta spacecraft weighs three tons and is almost cube shaped with measurements of 2.8-by-2 and 2-by-2 meters. Two large solar panels with a total area of 64 square meters provide electricity to all its systems and instruments. On one side is an antenna with a diameter of 2.2 meters for communications, while on the other the 100-kilo Philae lander module is attached.
The development and construction of Rosetta, under the leadership of the German company Astrium as prime contractor, involved more than 50 companies in 14 European countries, the U.S. and Canada.


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