Rosetta wakes up to prepare for its date with comet

Europe’s Rosetta space mission has sent its first signal to Earth, indicating that it is on course to be the first spacecraft to land on a comet. 

Rosetta, launched in 2004 and made possible with significant input from British industry and academia, is in pursuit of Comet 67P/Churyumov-Gerasimenko, where it will become the first space mission to attempt a landing on a comet’s surface, and the first to follow a comet as it swings around the Sun.

The signal, received yesterday January 20, 2014 by NASA’s Goldstone and Canberra ground stations at 18:18 GMT/19:18 CET, was confirmed by ESA’s space operations centre in Darmstadt.

Operating on solar energy, the Rosetta comet chaser was placed into a deep space ‘slumber’ in June 2011 as it cruised out to a distance of nearly 800 million kilometres from the Sun, beyond to the orbit of Jupiter.

According to a statement, Rosetta’s orbit has brought it back to within 673 million kilometres from the Sun, where there is enough solar energy to fully power the spacecraft

Still approximately nine million kilometres from the comet, Rosetta was reactivated by its pre-programmed internal ‘alarm clock’. After warming up its key navigation instruments, coming out of a stabilising spin, and aiming its main radio antenna at Earth, Rosetta sent a signal to let mission operators know it had survived the most distant part of its journey.

Since its launch, Rosetta has made three flybys of Earth and one of Mars to help it on course to its rendezvous with 67P/Churyumov-Gerasimenko, encountering asteroids along the way.

The spacecraft will now undergo a series of checks, after which the 11 instruments on the orbiter (and ten on the lander) will be turned on and prepared for studying the comet.

Rosetta’s first images of 67P/Churyumov-Gerasimenko are expected in May, when the spacecraft is two million km from its target. Towards the end of May, the spacecraft will execute a major manoeuvre to line up for its rendezvous with the comet in August.

After rendezvous, Rosetta will start with two months mapping the comet’s surface, and will also make measurements of the comet’s gravity, mass and shape, and assess its gaseous, dust-laden atmosphere. The orbiter will also probe the plasma environment and analyse how it interacts with the Sun’s outer atmosphere, the solar wind.

Using these data, scientists will choose a landing site for the mission’s 100kg Philae probe, which is scheduled for  November 11, 2014. Negligible gravity on the comet will require Philae to use ice screws and harpoons to stop it from rebounding back into space after touchdown.

Among its wide range of scientific measurements, Philae will send back a panorama of its surroundings, as well as very high-resolution pictures of the surface. It will also perform an on-the-spot analysis of the composition of the ices and organic material, including drilling down to 23cm below the surface and feeding samples to Philae’s on-board laboratory for analysis.

Speaking about the Philae lander’s UK-led Ptolemy instrument – a laboratory the size of a small shoebox – Ian Wright, Professor of Planetary Sciences at The Open University, said: ‘Once the Philae lander touches down on the comet, we will be looking for evidence recorded in remnants of debris that survived the processes of planet formation.

‘This is not merely a period of pre-history, but one that pre-dates the origin of life itself. Our quest is to gain insights into this transitional era, which took place more than 4.5 billion years ago.’

Rosetta’s UK industry partners include Astrium, the major subcontractor for the mission platform, and Surrey Satellite Technology, which designed a wheel that will stabilise the probe as it descends and lands on the comet.