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 The BBC's Pallab Ghosh"A few hours after it lands the world will hear the first sounds from another planet"  real 28k  |
Mars Polar Lander on track
Touchdown is set for 2001 GMT Friday |
The Mars Polar Lander is nearing its destination and is due to touch down on the Red Planet's south pole just after 2001GMT on Friday.
A signal confirming that the spacecraft is on the surface of the Red Planet should arrive on Earth at 2039GMT.
The lander's main purpose is to search for evidence of water in the Martian soil and to study its atmosphere - but it is also equipped with a microphone intended to send back the sounds from another world for the very first time.
Scientists at Nasa's Jet Propulsion Laboratory in Pasadena, California, who are controlling the mission, remain confident if cautious about its success.
"Entry, descent and landing are very complex, and a lot of things have to go correctly," said project manager Richard Cook. "That's just part of the risk associated with the mission."
Climate Orbiter
If Friday's landing is a success, the Polar Lander will join Mars Pathfinder and the two Viking spacecraft as the only spacecraft to explore the surface of the Red Planet.
Nasa scientists are anxious, however, because only 10 weeks ago the Polar Lander's sibling spacecraft, the $125m Mars Climate Orbiter, burned up in the planet's atmosphere because of a mix-up over metric and English units (pounds, feet and inches).
And in 1993, the Mars Observer, a $1bn Nasa spacecraft, disappeared just before going into orbit around the Red Planet. It is believed to have exploded as its fuel lines were being pressurised.
When the spacecraft arrives at Mars, it must enter the atmosphere through a corridor that is 10 km (6 miles) wide and 40 km (25 miles) long. The corridor begins about 125 km (78 miles) above the surface.
Weighing 576kg (1,270 pounds), the Polar Lander is equipped with a robotic arm, radio antennae, imaging devices and solar panels for power.
The spacecraft is 3.5 metres wide and 1.0 m tall |
For just under two minutes during the descent, a camera directed toward the south polar region of Mars will capture and store a series of about 20 images unique in the exploration of Mars.
The camera, known as the Mars Descent Imager, or Mardi, will be positioned between the legs of the Mars Polar Lander, with the exhaust of the hydrazine engines in view. It will begin clicking its shutter after the lander vehicle's heat shield has been jettisoned - about 6.5 km (4 miles) above the surface.
The final few images will be taken after the parachute has been jettisoned, about a thousand metres (0.6 miles) above the surface, and as the craft makes a controlled descent to the frigid northern edge of the Martian south pole's layered terrain.
The descent camera pictures will be used to interpret ground features and will aid in the mission's main purpose, studying the layers of ice and dust covering the polar region.
Sound and vision
The first signals - and confirmation of a success - are not expected to reach Earth until 38 minutes after touchdown, provided an antenna is pointed properly.
Target: The South Pole's layered terrain |
Nasa is hoping for a status report, weather readings and black-and-white images by the end of Friday.
Clearer pictures and sound clips from a microphone could be returned by the weekend. Nasa hopes to relay data through the Mars Global Surveyor, which has been orbiting Mars since 1997.
Search for water
The Polar Lander will try to find evidence that the atmosphere was once warmer and thicker.
Its landing site is an area where climate changes are believed to have caused layering of dust and ice that could be read like the rings of a tree trunk.
If water is found, large underground ice deposits could also prove invaluable for future human missions to Mars, providing both water to drink and the raw material for fuel, scientists say.
"That could make the process of eventually settling on Mars that much easier," said David Paige of the University of California-Los Angeles, one of the chief scientific investigators on the project.
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30 Nov 99 | Sci/Tech |
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Polar lander ready for Mars |
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30 Nov 99 | Sci/Tech |
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Martian mysteries under microscope |
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11 Nov 99 | Sci/Tech |
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Orbiter loss blamed on 'silly mistakes' |
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