Rosetta's comet lander readies for its launch

Rosetta that was launched in 2004 is now preparing to enter its last phase of the mission. Ten years later, on August 6, the spacecraft began orbiting 67P, and its 11 instruments started scrutinizing myriad characteristics of the comet (SN: 9/6/14, p. 8). Those instruments, plus the cameras and sensors on the Philae lander, are designed to map 67P, determine what it’s made of and observe how its chemistry might change as it swings around the sun.

On November 12, Rosetta will sidle up to a comet, steady itself and drop a 100-kilogram robotic lander toward the hunk of rock, dust and ice. The lander, named Philae, will drift through space, tugged only slightly by the gravity of the comet, commonly called 67P. Mission scientists will be holding their breath for what could be several anxiety-filled hours to see if Philae lands where and how it’s supposed to.

The exercise — the first attempt to set a lander on a comet — is as nerve-racking as landing on Mars or the moon, with some added challenges. Comets and other small space rocks have much less gravity than planets or moons, which is why it will take Philae close to seven hours to float to comet 67P’s surface. Then there’s the comet’s speed: Rosetta will drop the lander toward 67P as the comet shoots through the solar system at 55,000 kilometers per hour.

Add to that a comet's unpredictable nature: At any moment and without warning, 67P might spew out jets of gas and dust. Such eruptions could blow the spacecraft off course or skew the lander’s trajectory so it hits a boulder or misses its mark.

Early in the mission, scientists estimated that Philae had a 70 to 75 percent chance of successfully touching down on the comet, officially known as 67P/Churyumov-Gerasimenko. They made that prediction when they thought the comet was shaped like a potato. In July, Rosetta began sending pictures of 67P, indicating it looks more like a rubber duck — two masses connected by a thin neck. The new shape adds a bit more uncertainty to Philae sticking its landing.

Video Transcript :

"The European Space Agency's Philae robot is preparing for an extraordinary landing on an ambitious target: comet 67P/Churyumov-Gerasimenko.

Out there in the cold depths of space, somewhere between Mars and Jupiter, a spacecraft called Rosetta is coyly playing with a comet. Scientists call this comet 67P/Churyumov-Gerasimenko. Since August, the spacecraft has been swooping in and around the 4-kilometer long comet, snapping selfies with it and taking close-ups of its craggy cliffs, crevices and boulders.

These striking images are the first to clearly show what the surface of comets can look like. They also helped scientists pinpoint just the right spot for a daring operation: To set a lander down on 67P’s surface.

After weeks of pouring over the images mission scientists finally selected a relatively flat spot on the head of the comet for their lander, Philaeto settle into. But getting down to the surface won’t be easy.

It will require a complex set of circles around the comet and a separation at just the right point in one of those orbits.

This separation is slated to take place on November 12. That day, Rosetta will swing to within 23 kilometers of the comet and drop Philae off its backside. The lander will then drift through space toward 67P. And, if all goes well, it will arrive on the comet roughly seven hours later.

Then the 10 instruments aboard the robot will probe the comet from the inside out. Each instrument is designed to look at specific features of the comet, such as its internal structure and the chemical elements and molecules that make up its dust. This data, along with Rosetta’s analysis of 67P, will help scientists really get a handle on what comets are and what happens to them as their orbits take them closer to the sun.

A close look at the comet could also take us back in time to the beginning of the solar system. That’s because comets appear to be time capsules that may have preserved some of the earliest materials found in the solar system. Looking at those pristine features may help scientists and astronomers answer fundamental questions about how the planets formed and possibly even how water and other life ingredients made their way to Earth.

But first we’ll have to wait for that long-sought signal saying yes, Philae has made its touchdown.

Images, graphics and animations courtesy of DLR German Aerospace Center and ESA; Narrated and produced by Ashley Yeager"

ORIGINAL: Science Dump
by Andreea
11/08/2014