Scientists Await First Call From Beagle (Forwarded)
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25 December 2003
Scientists Await First Call From Beagle
Early this morning, the Beagle 2 spacecraft landed on the surface of Mars at the
end of a 250 million mile (400 million km), six-month trek to the Red Planet.
Although the first attempt to use NASA's Mars Odyssey orbiter to communicate
with the lander three hours later was unsuccessful, scientists and engineers are
still awaiting the best Christmas present possible -- the first faint signal to
tell them that Beagle 2 has become only the fourth spacecraft to make a
successful landing on Mars.
"This is a bit disappointing, but it's not the end of the world," said Professor
Colin Pillinger, lead scientist for the Beagle 2 project.
"We still have 14 contacts with Odyssey programmed into our computer and we also
have the opportunity to communicate through Mars Express after 4 January."
The next window to receive confirmation that Beagle 2 has successfully landed
and survived its first night on Mars will be between 10 pm and midnight (GMT)
tonight, when its simple carrier signal (rather than the tune composed by Blur)
may be picked up by Jodrell Bank radio observatory in Cheshire, UK. This has a
much greater chance of success because the giant telescope is able to scan the
entire side of the planet facing the Earth.
Another overflight by Mars Odyssey will take place around 18:15 GMT tomorrow
evening, followed by daily opportunities to contact Beagle 2 via the Mars
Odyssey spacecraft and the radio telescopes at Jodrell Bank and Stanford
University in the United States.
There are several possible explanations for the failure of Odyssey to pick up
Beagle 2's signal. Perhaps the most likely is that Beagle 2 landed off course,
in an area where communication with Mars Odyssey was difficult, if not
impossible. Another possibility is that the lander's antenna was not pointing in
the direction of the orbiter during its brief passage over the landing site. If
the onboard computer had suffered a glitch and reset Beagle 2's clock, the two
spacecraft could be hailing each other at the wrong times.
The Beagle 2 lander entered the thin Martian atmosphere at 2:47 GMT today.
Travelling at a speed of more than 12,500 mph (20,000 km per hour), the probe
was protected from external temperatures that soared to 1,700 C by a heat shield
made of cork-like material.
As friction with the thin upper atmosphere slowed its descent, onboard
accelerometers were used to monitor the spacecraft's progress. At an altitude of
about 4.5 miles (7.1 km), Beagle's software was to order the firing of a mortar
to deploy a pilot parachute, followed one minute later by deployment of the 33
ft (10 m) diameter main parachute and separation of the heat shield.
At a few hundred metres above the surface, a radar altimeter was to trigger the
inflation of three gas-filled bags. Cocooned inside this protective cushion,
Beagle 2 was expected to hit the rust-red surface at a speed of about 38 mph (60
km/h). As soon as the bags made contact with the surface, the main parachute was
to be released so that the lander could bounce away unhindered. Like a giant
beach ball, the gas bag assembly was expected to bounce along the surface for
several minutes before coming to rest at 2:54 GMT.
Finally, a system of laces holding the three gas-bags onto the lander was to be
cut, allowing them to roll away and drop Beagle 2 about 3 ft (1 m) onto the
surface. The whole descent sequence from the top of the atmosphere to impact was
to take less than seven minutes.
The "pocket watch" design of Beagle 2 ensured that it would turn upright
irrespective of which way up the little lander fell. After the onboard computer
sent commands to release the clamp band and open the lid, the way would be clear
to deploy the four, petal-like solar panels and initiate charging of the batteries.
Confirmation of the successful landing would be provided by a musical "beeping"
signal of 9 digitally encoded notes, composed by British rock group Blur. This
signal should be picked up by Mars Odyssey as it passes overhead and then
relayed to Earth.
Notes for editor:
Beagle 2 was targeted to land within an ellipse, 30 km long and 5 km wide, on
Isidis Planitia, a large lowland basin near the Martian equator. However, the
exact location of the landing site depended on factors such as the angle of
descent and wind speed.
The landing site (11 N, 90 E) was chosen for its low elevation, since a greater
depth of atmosphere would assist the parachute in braking the lander's descent.
Its equatorial location also means that temperatures are warmer, minimising the
amount of insulation (and hence mass) needed to protect the lander from the cold
Martian night. The relatively flat site was also thought to be neither too dusty
nor too rocky to threaten a safe landing (but rocky enough to be interesting for
Sunset at the Mars landing site today was at 07:15 GMT (18:35 local solar time).
Beagle 2 is scheduled to shut down and conserve power during the cold Martian
night, when temperatures may plummet to -80 C. Sunrise will take place at 20:02
GMT on Mars (07:02 local solar time).
Beagle 2 was launched with the European Space Agency's Mars Express orbiter on 2
Beagle 2 was named to commemorate Charles Darwin's five-year voyage around the
world in HMS Beagle (1831-36). Its main objective is to search for signs of life
-- past or present -- on the Red Planet.
By the time it arrived on the Martian surface, Beagle 2 weighed 33 kg, including
9 kg of science instruments. This is the most ambitious experiment package ever
flown in space.
For further details on Mars Express and Beagle 2 see the following websites:
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