Phobos-Grunt Mars probe will crash to Earth on Sunday

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Phobos-Grunt Mars probe will crash to Earth on Sunday

Alok Jha, science correspondent

guardian.co.uk, Thursday 12 January 2012 12.57 EST

A defunct Russian spacecraft is due to re-enter the atmosphere sometime after midday (GMT) on Sunday, say scientists who are watching its orbit closely.

They cannot predict precisely where it will hit the Earth, but say the most likely scenario is that it will splash down in the ocean. However, most of the world's major cities, including London and New York, are potentially in the firing line.

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It is the largest planetary rocket ever built by the Russian space agency, Roscosmos, and was intended to land on the Martian moon Phobos and bring samples back to Earth. The mission also included a Chinese-built orbiter and containers of bacteria to test their survival in space.

But the spacecraft's rocket boosters failed to ignite after it had been launched into a parking orbit around the Earth in November. Despite repeated attempts to contact it from the ground, Phobos-Grunt remained stuck in orbit and the Russian authorities decided to abandon the mission.

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Any parts that do not burn up during re-entry will most likely land in the sea. To predict exactly where, scientists need to know when the probe starts to make its final descent into the Earth's atmosphere. "Because we're going through the very tenuous rarefied parts of the atmosphere, you can see orders of magnitude changes in density occurring over a short period of time, unpredictably," said Crowther. "That will dictate the lifetime of the orbit. Even on the last orbit, which takes 90 minutes to complete, the uncertainty is still plus or minus nine minutes."

The probe will be travelling at 8km/s during this final orbit of the Earth, so the uncertainty in pinpointing the exact location of the landing is 4,300km.

Last week, officials at the Russian space agency said that up to 30 fragments, weighing a total of 200kg, might reach the Earth's surface. The 10 tonnes of fuel and oxidiser are likely to burn up on re-entry or be vented into space as the probe's orbit decays.

The parts most likely to survive include the cone-shaped sample-return capsule, which is protected with a heat shield – though even that is uncertain. "[it] is designed to return to atmosphere and survive re-entry on its own. If it comes in on this complex with things going on around it, it's not going to see clean air and it's very likely that it will also be destroyed," said Crowther.

If any parts of the probe cause damage to people or property on the ground, which Crowther said was highly unlikely, any costs would have to be met by the Russian government, according to United Nations conventions. If any parts of the probe landed in the UK, the UK government would be obliged to pay for its return to Russia.

Full report

And for the Geeky:

Phobos-Grunt - Reentry Watch: http://zarya.info/Diaries/Misc/PhobosGrunt3.php

Map: http://reentrynews.aero.org/2011065a.html

[traveller]

What goes up.........

[nebula]

What goes up.........

Yeah, it just wasn't supposed to!