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First, you will need a significant piece of space hardware. Second, you will need to launch it having meticulously planned its convoluted trajectory through the solar system. Third, wait 12 years for the craft to reach the comet. Fourth, and with fingers crossed, launch a landing probe from the craft on to the 2.5 mile wide comet 67 P/Churyumov-Gerasimenko, while all are hurtling through space at around 25,000 miles per hour.

So far so good. The Rosetta spacecraft woke up from its self-induced 30-month hibernation on January 20, having slumbered to conserve energy. Now it continues on its final leg of the journey — a year-long trek to catch the comet.

Visit the European Space Agency (ESA) Rosetta mission home page here.

From ars technica:

The Rosetta spacecraft is due to wake up on the morning of January 20 after an 30-month hibernation in deep space. For the past ten years, the three-ton spacecraft has been on a one-way trip to a 4 km-wide comet. When it arrives, it will set about performing a maneuver that has never been done before: landing on a comet’s surface.

The spacecraft has already achieved some success on its long journey through the solar system. It has passed by two asteroids—Steins in 2008 and Lutetia in 2010—and it tried out some of its instruments on them. Because Rosetta’s journey is so protracted, however, preserving energy has been of the utmost importance, which is why it was put into hibernation in June 2011. The journey has taken so long because the spacecraft needed to be “gravity-assisted” by many planets in order to reach the necessary velocity to match the comet’s orbit.

When it wakes up, Rosetta is expected to take a few hours to establish contact with Earth, 673 million km (396 million mi) away. The scientists involved will wait with bated breath. Dan Andrews, part of a team at the Open University who built one of Rosetta’s on-board instruments, said, “If there isn’t sufficient power, Rosetta will go back to sleep and try again later. The wake-up process is driven by software commands already on the spacecraft. It will wake itself up autonomously and spend some time warming up and orienting its antenna toward Earth to ‘phone home.’”

If multiple attempts fail to wake Rosetta, it could mean the end of the mission.

Rosetta should reach comet 67P/Churyumov-Gerasimenko in May 2014, at which point it will decelerate to match the speed of the comet. In August 2014, Rosetta will enter orbit around the comet to scout 67P’s surface in search of a landing spot. Then, in November 2014, Rosetta’s on-board lander, Philae, will be ejected from the orbiting spacecraft onto the surface of the comet. There are a lot of things that need to come together perfectly for this to go smoothly, but space endeavors are designed to charter unknown territories, and Rosetta will be doing just that.

If Rosetta manages this mission successfully, it will make history as the first spacecraft to land on the surface of a comet. Success is by no means assured, as scientists have no idea what to expect when Rosetta arrives at the comet. Will the comet’s surface be icy, soft, hard, or rocky? This information will affect what kind of landing the spacecraft can expect and whether it will sink into the comet or bounce off. Another problem is that comet 67P is small and has a weak gravitational field, which will make holding the spacecraft on its surface challenging, even after a successful landing.

At a cost of €1 billion ($1.36 billion) it’s important that we get some value for our money with this mission. To ensure we do, Rosetta was designed to help answer some of the most basic questions about Earth and our solar system, such as where water and life originated, even if the landing doesn’t work out as well as we hope it will.

Comets are thought to have delivered some of the chemicals needed for life, including water to Earth and possibly other planets. This is why comet ISON, which sadly did not survive its close encounter with the Sun, had created excitement among scientists. If it had survived, it would have been the closest scientists could get to a comet with modern instruments.

Comet ISON’s demise means Rosetta is more important than ever. Without measuring the composition of comets, we won’t fully understand the origin of our planet. Comet 67P is thought to have preserved the very earliest ingredients of the solar system, acting as a small, deep-freeze time capsule. The hope is that it will now reveal its long-held secrets to Rosetta.

Andrews said, “It will be the first time a spacecraft will approach a comet and actually stay with it for a prolonged period of time, studying the processes whereby a comet ‘switches on’ as it approaches the Sun.”

Once on the comet’s surface, the Philae lander will deploy instruments to measure different forms of the elements hydrogen, carbon, nitrogen, and oxygen in the comet ice. This will allow scientists to understand the composition of the water and organic components that were collected by the comet 4.6 billion years ago, at the very start of the Solar System.

Read the entire article here.

Video: Rosetta’s Twelve-Year Journey to Land on a Comet. Courtesy of European Space Agency (ESA) Space Science.