- Europe's Rosetta spacecraft has launched successfully
on its daring journey to chase and land on a comet.
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- The £600m probe lifted off at 0717 GMT from its
launchpad in Kourou, French Guiana on an Ariane 5 rocket after being delayed
for two days in a row.
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- Rosetta is primed for a 7bn-km journey to Comet 67P/Churyumov-Gerasimenko.
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- The probe is still attached to the upper stage of its
Ariane rocket and is now coasting in an elliptical orbit above Earth preparing
to separate.
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- "The first part of the mission has passed well,"
said Jean Yves Le Gall, chief executive of rocket company Arianespace.
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- Once in orbit around the mountainous ball of ice and
dust in 2014, the craft will despatch a small lander to the comet's surface
to study its chemistry.
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- Peculiar path
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- This mission used a very specific launch instant rather
than the typical launch window used to put most satellites into Earth orbit.
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- After lift-off, booster separation and burn-out of the
central core stage of the Ariane 5 rocket, the upper stage entered a prolonged
ballistic phase. This will be followed by a delayed ignition of almost
17 minutes.
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- After this burn, Rosetta will separate from the upper
stage and set off on an Earth-escape trajectory.
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- This will set the spacecraft on its long Solar System
journey that will take around the Sun four times, around Mars once (2007),
the Earth three times (2005, 2007, 2009), and into the asteroid belt twice.
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- The rendezvous with Comet Churyumov-Gerasimenko is set
for early 2014.
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- At this time, the comet will be cold and inactive, and
Rosetta will be able to release a washing-machine-sized lander, called
Philae, on to the object's surface.
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- Life's beginnings
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- As the comet moves into the inner Solar System, radiation
from the Sun will make its ices sublime - they will turn direct from solid
to gas. Material will be ejected at supersonic speeds.
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- Gas and dust will be thrown out around the comet to form
a coma, and away from the comet to form tails.
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- The Rosetta orbiter and lander will watch and record
these events as the comet hurtles along at speeds up to 135,000km/h.
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- Scientists are keen to study comets close up because
they are thought to contain materials that have remained largely unchanged
since the formation of the Solar System 4.6bn years ago.
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- They may give clues as to why the Solar System evolved
the way it did. Some researchers think comet impacts may even have seeded
the early Earth with the chemistry needed for life to develop.
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- © BBC MMIV
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- http://news.bbc.co.uk/2/hi/science/nature/3522535.stm
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