Artist's impression of the Rosetta Spacecraft (Credit: ESA - C. Carreau)

Rosetta’s hibernation mode starts today (8th June 2011) and will last until January 2014, during which time the spacecraft will reach its maximum distances from the Sun (about 800 million kilometres) and Earth (about 1000 million kilometres). UK scientists and engineers involved in this exciting mission are hoping Rosetta will unlock the hidden secrets of comets and teach us more about the origin of these huge, dirty snowballs.

Dr David Parker, Director of Science, Technology and Exploration at the UK Space Agency, said, “Rosetta really has earned this break. Rosetta’s primary mission hasn’t even started yet but since the launch in 2004 it has been on a non-stop cosmic ‘road-trip’, busily providing us with a wealth of information about our solar system. Everyone at the UK Space Agency and all the UK scientists and engineers who have made this mission possible are eagerly awaiting Rosetta’s final rendezvous before it chases a comet into the Sun.”

Rosetta has been a huge success so far. On its journey to the comet, it has revealed the battered world of Asteroid Lutetia, showing it is most probably a primitive survivor from the violent birth of the Solar System; spotted an anticyclone over Earth; tracked asteroid Steins; and taken pictures of the Moon and Mars. Once the spacecraft reaches the comet, its primary mission will begin, making it the first spacecraft to orbit a comet’s nucleus, examining from close proximity how a frozen comet is transformed as it approaches the Sun.

Lutetia at Closest approach.
Credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

At precisely 10:00 GMT on 20 January 2014, a timer will wake the spacecraft, which, seven hours later, will transmit a check signal to let mission controllers know that the spacecraft has woken.

When the spacecraft eventually arrives in the comet’s vicinity in May 2014, its thrusters will slow the spacecraft, so it can match Comet 67P/Churyumov-Gerasimenko’s orbit, allowing it to edge closer to the black, dormant nucleus until it is only a few dozen kilometres away. After this process, taking approximately 6 months, the spacecraft will release a small lander onto the icy nucleus of the comet and then spend the next two years orbiting the comet as it heads towards the Sun.

Rosetta’s ten-year expedition began with an Ariane-5 launch from Kourou in French Guiana.

Unfortunately, no existing rocket, not even the powerful European-built Ariane-5, has the capability to send such a large spacecraft directly to Comet 67P/Churyumov-Gerasimenko.

Instead, Rosetta was bounced around the inner Solar System like a ‘cosmic billiard ball’, circling the Sun almost four times during its ten-year trek to Comet 67P/Churyumov-Gerasimenko.

During this lengthy journey Rosetta entered an asteroid belt twice and gained velocity from gravitational ‘kicks’ provided by close fly-bys of Mars (2007) and Earth (2005, 2007 and 2009).