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The BBC's Lindsay Marnoch
"There have been anxious faces at NASA mission control"
 real 28k

Richard Cook, MPL Roject Manager
"It's not unexpected"
 real 28k

The entry procedure
Nasa simulation of MPL's landing
 real 28k

Probing the surface
Two probes should have penetrated the Martian surface
 real 28k

Saturday, 4 December, 1999, 14:08 GMT
Nasa hopeful despite Mars silence
scientists at mission contorl The team of scientists at mission control make a desperate plea:

Nasa scientists are continuing their attempts to make contact with the Mars Polar Lander spacecraft, which is believed to have landed but has failed to send a signal to mission control.

Latest estimates indicate that the MPL touched down on a gentle slope of about two degrees near the edge of a ridge within an "amphitheatre".

Artist drawing of MPL The MPL had a complicated set of landing manoeuvres
The Deep Space 2 microprobes, which should have separated from the MPL during entry, are believed to have hit the surface about 60km (35 miles) north of the lander.

Yet attempts to communicate with the lander and the two microprobes during the first 12 hours after the scheduled landing time did not succeed.

The Deep Space 2 team at Nasa's Jet Propulsion laboratory in Pasadena will now try to contact the probes every two hours.

The Mars Polar Lander's next opportunity to contact Earth will be at 0430 GMT on Sunday.

Project manager Richard Cook said he remained optimistic despite the setbacks.

"I am very confident that the lander survived the descent," he said.

Last contact

Possible Problems
Computer in 'standby' mode
Compass malfunction
Landing angle too steep
Destroyed on entry
Did not separate from cruise-craft
The spacecraft was due to touch down on the surface of the red planet at 2015 GMT on Friday. Signals from it were detected up to 10 minutes before the scheduled landing, but nothing has been heard since then.

There are several theories as to why none of the three craft has functioned as planned.

The most likely scenario, according to Mr Cook, is that the computer in the MPL has switched into "standby" mode, possibly to correct an error in its instruments.

It would not come out of its safe mode until early Sunday morning GMT, he added.

Richard Cook Project Manager Richard Cook says he's still "upbeat"
Another possibility is that the craft is "lost" due to a malfunction in its gyro compass. If it did not know its own location on Mars it would not be able to locate Earth.

The angle of landing for either the MPL or the probes could also have been too steep for the antennas to function correctly.

More catastrophic scenarios are that the craft was destroyed on entry, or did not separate from the cruise-craft, which would have sent it plummeting to the Martian surface.

Latest data suggests however that all three craft did land.

If mission controllers fail to make contact by Sunday evening GMT they will try to communicate by using the Mars Global Surveyor spacecraft, currently orbiting the planet, as a relay system.

Nevertheless, many privately realise that the longer that the MPL stays silent the less are the chances that it will ever be heard of again.

Experiments

Scientists sent the MPL to Mars to learn about the planet's climate by studying layers of dust and possibly ice during the 90-day mission.

The Martian South Pole Target: The Martian South Pole's layered terrain
The probes were designed to separate from the MPL and smash into the surface at about 640km/h (400 mph).

They would then begin operating compact microlaboratories, collecting and testing subsurface soil samples, heating them in a tiny oven and scanning them to check for signs of water.

The MPL even had a microphone on board to record the first sounds from another world.

Loss of the lander would be a devastating blow to Nasa. Only 10 weeks ago, the lander's sibling spacecraft, the $125m Mars Climate Orbiter, burned up in the planet's atmosphere because of an embarrassing mix-up over imperial measurements (pounds, feet and inches) and metric units.

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See also:
02 Dec 99 |  Sci/Tech
Mars Polar Lander on track
30 Nov 99 |  Sci/Tech
Polar lander ready for Mars
30 Nov 99 |  Sci/Tech
Martian mysteries under microscope
11 Nov 99 |  Sci/Tech
Orbiter loss blamed on 'silly mistakes'

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