Tuesday, September 7, 1999 Published at 15:45 GMT 16:45 UK
Mir drifts free
On its own, but for how long?
By BBC News Online Science Editor Dr David Whitehouse
Mir has gone into "free drift" mode as a new onboard computer takes control of the unmanned space station.
The drift, or free flight, is necessary to reduce power consumption so that Mir can survive for many months in space before a possible return by cosmonauts.
The last crew left on 27 August, just ten days before Mir would have celebrated ten years of continuous crewing.
The new onboard computer fires Mir's thrusters, keeping its solar panels pointed at the Sun so its batteries remain charged. It can be programmed by ground controllers.
It replaces a more cumbersome control computer that needed constant attention by cosmonauts.
Russia had said that it would decide Mir's fate this year. But space officials now say that a decision on the future of Mir will be made next spring. They add that the 13-year-old station is in good condition. Mission control says Mir could work quite well until 2005.
If the decision to abandon Mir is made a final crew will visit it to make preparations for deorbiting the station, and a cargo ship will deliver fuel to assist its crash back to Earth.
Some experts do not think that it will be possible to regain control of Mir if the new computer fails and Mir goes into a chaotic spin.
In an emergency, the Progress M42 unmanned supply craft, which is still docked with Mir, could be used to stabilise the space station. It would be a tricky manoeuvre though.
It is clear that Russian space officials will wait until the last possible moment before they give up on Mir. It requires $250 million a year to operate and officials know that, in space terms, that is not a lot of money. But they also know they simply have not got it.
Last week Russia signed a joint space pact with China that included the suggestion that the two nations could work on space stations together.
Some are speculating that China could finance Mir's future. Others say that China would prefer to have a space station all of its own, even if it is based on the Mir design.