We know how much mass will burn up in the atmosphere and how much will come into contact with Earth

Vladimir Solovyov, Mir flight director

A Progress cargo ship blasted off from the Baikonur cosmodrome in Kazakhstan early on Wednesday, and will attempt to dock with the 15-year-old orbiting platform on Saturday.

"The rocket is in orbit and all systems are working well," a mission control spokeswoman said. "It is due to dock with Mir on 27 January at 0830 (0530 GMT)."

If all goes to plan, the cargo ship will lower Mir's altitude, causing it to enter the dense layers of the Earth's atmosphere where most of the station will burn up.

Debris is expected to fall into the Pacific Ocean in a designated area that covers about 6,000 kilometres by 500 kilometres. This should be well to the east of Australia and New Zealand. The date of 6 March has been set for the final descent.

Funding problems

Mir was launched on 20 February, 1986, and was regarded as the jewel in the crown of the Soviet space programme. It has stayed in service well beyond the five years originally envisioned.

The lessons learned about living in orbit have been invaluable and will benefit all future, manned, space exploration. But lack of finance in the new Russia and a string of accidents, including a fire and a near-fatal collision with an unmanned cargo ship in 1997, have compromised the future viability of the station itself.

A decree was finally signed by the Russian Government late last year confirming the order to scuttle the platform.

It was a decision that was welcomed by the United States and its partners now building the International Space Station (ISS). They had argued for some time that Russia should concentrate its resources on the new ISS project.

Docking concerns

Russian space officials have had some difficulty controlling the Mir space station in recent days and weeks.

Mir has been in space for 15 years

A combination of battery, computer and gyroscope problems led to a postponement of the Progress launch last Thursday.

But flight controllers insist the situation is under control and should not prevent a satisfactory docking from taking place at the weekend. Once attached to Mir, the cargo ship will be used to push the station to destruction.

"The engine of the cargo ship, loaded with fuel, will be started up many times so that it will act like a tanker and a tugboat at the same time," said Mir flight director Vladimir Solovyov, describing the scuttling procedure.

Emergency crew

"Two engines will be turned on at the same time, the main engine and reserve engine, followed by a series of braking actions. In this way, the station will be directed down to the point where it should land."

He added: "We understand that at a height of 140 kilometres (85 miles) above the Earth's surface, the solar batteries will burn up first, and mechanisms will begin to break apart. At around 90-100 kilometres (55-60 miles), we know that the construction itself will begin to break apart.

"We know how much mass will burn up in the atmosphere and how much will come into contact with Earth, and we know exactly what will fall on to Earth."

Should anything go awry with the automated docking on Saturday, an emergency crew will blast off for Mir to direct from orbit further attempts at a link-up.