The ITAR-Tass news agency initially quoted Viktor Blagov of the Mission Control Center as saying a cargo ship attached to Mir which already is slowly descending toward Earth would fire its engines Thursday to lower the station's orbit by about four miles.
But several hours later, Blagov was quoted as saying the cargo ship must remain linked to Mir for longer than expected because the space agency cannot afford to send a replacement.
That will use up all the cargo ship's fuel, leaving none to control the descent maneuver. However, even without the assist from the cargo ship, Mir will likely lower its orbit to the same degree early next month, Blagov said.
A cargo ship due to arrive in September a month late will assist Mir in further lowering its orbit.
If Mir's orbit isn't controlled, the 130-ton station would fall back to Earth within two years on its own and some big pieces could hit populated areas, space officials warned.
Mission Control spokesman Valery Lyndin confirmed that the maneuver scheduled for Thursday was canceled, but would not comment on the reasons for the decision.
Several cargo ships, docked to Mir one at a time, are supposed to push the space station down from 250 miles above Earth to 75 miles, before it burns up in the atmosphere in December 1999. A few large fragments are likely to fall into the ocean.
The next cargo ship is now scheduled to be launched in September, instead of August.
Yuri Semyonov, head of the state-run RKK Energiya corporation that built Mir and has been running it since it was put in orbit in 1986, has said Russia might be forced to discard the station as early as this fall because of the space industry's desperate cash shortage.
Semyonov said last week that the government owes Energiya $70 million from last year and hasn't paid any bills so far this year.
According to Blagov, Russia will need four regular cargo ships to gradually lower Mir's orbit and a fifth one, with a larger amount of fuel, to give the station a final farewell push.
Russia hopes to keep Mir in orbit until 1999, when it will be replaced by the international space station.
Written by Vladimir Isachenkov
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