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British scientists refuse to give up hope of hearing from Mars probe

Posted on: Monday, 29 December 2003, 06:00 CST

LONDON -- Scientists struggled Sunday to understand why they have failed to make contact with Europe's first Mars probe, four days after the Beagle 2 craft was supposed to touch down on the Red Planet to begin its search for life.

Repeated attempts to pick up the vessel's call signal have struck out, but Beagle's creators say they still are hopeful of hearing from the lander.

NASA's Mars Odyssey, which is orbiting the planet, again passed over the spot late Sunday where scientists believe the probe touched down on Christmas Day, but it failed for a fourth time to pick up a signal from Beagle. Another overflight is scheduled for early today.

But project leaders say their best hope of contacting Beagle will come when its mother ship, Mars Express, enters a low orbit on Jan. 4.

"That is the communication line that has been tried and tested," said Gill Ormrod, spokeswoman for the British government's physics and astronomy research agency. "Until they have tried that several times, they will not give up."

Mars Express, which carried Beagle into space and set it free more than a week ago, is currently orbiting the planet as high as 117,000 miles above its equator.

On Tuesday, European Space Agency scientists at mission control in Darmstadt, Germany, will fire Mars Express' engine in an attempt to shift its orbit over one of the Martian poles necessary for it to survey the entire planet with its high-resolution camera and a powerful radar that can look for underground water.

Coming in for closer look

Scientists hope to gradually reduce the polar orbit and say that by Jan. 4, Mars Express should pass as low as 125 to 155 miles above the surface, enabling it to take close-up pictures and listen for Beagle.

The team at Britain's National Space Center in central England was striving Sunday to understand why it so far had failed to hear Beagle's call sign from the Martian surface.

Within hours of landing, the 143-pound probe, which has a robotic arm to take soil and rock samples, was supposed to unfold its solar panels and transmit a signal confirming its arrival.

But Britain's vast radio telescope at Jodrell Bank Observatory has failed three times to detect the probe in sweeps of the planet's surface.

Scientists at Stanford University also have joined the hunt, using a 150-foot dish antenna to listen for transmissions from the probe. They found nothing early Sunday. Mars Odyssey also has failed to pick up a signal in three overflights.

Team member Alan Wells said scientists were trying to understand what may have gone wrong.

"One possible explanation that has been raised for the apparent silence is the potential for incompatibility between the systems on board Beagle and those used by Mars Odyssey," he said.

Scientists also believe the probe may have landed off-course in an area where communication is difficult.

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