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During the descent phase the heat shield brakes the lander
from its interplanetary velocity, energy being lost by frictional
heating. Firing the parachute deployment device (PDD) through
a patch in the back cover, deploys a pilot chute whose role
is to divide the space craft into two sections whilst pulling
the main chute from its stowed position. Pyrotechnic bolts
explode to drop the heat shield.
The
gas-bags are inflated by a gas generator at 200m above the
surface (as detected by a radar altimeter) and on first contact
the device releases the main parachute so that the lander
can bounce away from underneath the canopy. When the whole
package comes to rest, a system of laces holding the three
gas-bags onto the lander is cut allowing them to reform and
roll away, dropping Beagle 2 onto the surface. Irrespective
of which way up it falls a hinge will open the clam shell
to start the science phase of the mission.

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