Five potential landing sites in the viewfinder Rosetta – Le Figaro

The European probe will examine five shortlisted for landing his measurement module Philae areas.

In early August, after a journey of ten years and more than 6 billion kilometers, Rosetta was beginning his first successful maneuvers into orbit around the comet 67P. Today, the spacecraft is just 60 km from the target, a kind of dirty snowball-shaped duck. On November 11, it will attempt an overview at an altitude of between 2.5 and 4 km Philae will drop a small lander cubic meter of a side. Europe could become the first power to land on a comet

The operation is dangerous. Philae will descend in free fall on the comet. As the attraction is weak, Philae, 100 kg on Earth, but only about 1 g of the comet, take four to six hours to fall in a parabolic trajectory. The shock of the tripod landing on the ground should trigger thrusters plaqueront the ground to keep it from bouncing or tipping. Meanwhile, two harpoons will be drawn to dock firmly to the surface. Depending on the hardness of the ground, a perfect stranger, they will sink a few inches or 2.5 meters deep. While science operations will start.

The choice of landing site looks crucial. This weekend, as many as 75 scientists involved in the mission were thus meeting the Toulouse Space Centre to reduce to five the list of ten potential candidates (A to I) established the previous week. Two of the selected sites are located on the body of the “duck”, A and C, the other three on the head, B, I and J. “The alphabetical order in no way foreshadows our preferences” would recall Philippe Gaudon Chief Rosetta project CNES. According to the website of the French space agency, the site I would be the only one to achieve unanimity among engineers and scientists …

The technical criteria to be met are numerous. There must be maximum sunshine for solar panels, high altitude so that the speed of contact does not exceed 4 km / h and the surface is as flat as possible. The gradual evaporation of ice in the comet as it approaches the Sun should not be too violent … Not to mention the expectations of scientists who dream to get their hands on complex organic molecules, remains of early moments of the solar system.

In mid-September, the European Space Agency (ESA) will decide and define a primary site and a plan B. The engineers will then attempt to reduce uncertainty on the point landing. For now, the error box is still about 1 km diameter, compared with the average diameter of 4 km of the comet. “The reduced to less than 300 m would be a great success,” says Philippe Gaudon. The convoluted shape of the comet partly explains the difficulties engineers. “Its gravitational field is very irregular, but this is not all: it is also very rugged to smaller scales: cliffs, crevices, rocks, etc.,” he explains. Philae is warned.