The failure of the computerized attitude control system onboard Mir is considered the most likely situation that would require sending a final crew to the Mir station. Thirty computers onboard Mir will be needed to accurately position the 13-ton outpost during the final re-entry maneuvering burns. The computers control complex electrically powered wheels, called gyrodynes, that are used for high-accuracy pointing of the station in space.

The station currently is remotely controlled by flight directors at the misison control center in Korolev, who radio commands for Mir's small thrusters to fire and keep the outpost positioned properly. The system, however, is not accurate enough to use to deorbit Mir.

Mir's computerized attitude control system is to be tested in mid-January, RKK Energia officials told Spaceflight Now. If problems surface, RKK Energia will switch gears and proceed with plans to send the prime burial crew, commander Salizhan Sharipov and flight engineer Pavel Vinogradov, to Mir. The Soyuz could be ready to fly within a couple of weeks.

The second scenario that could force a final manned mission to Mir is is the Progress M1 vehicle carrying fuel for the deorbit maneuver fails to automatically dock at the station. The unmanned cargo ship is scheduled to blast off on January 28 from the Baikonur Cosmodrome in Kazakhstan.

Again, Mir's computerized attitude control system needs to be functioning so the Progress can automatically berth at the station. If the docking fails, Sharipov and Vinogradov will be called upon to be ready to blast off within two weeks and dock the Progress at the station using a tele-operated system aboard Mir.

No joy ride
Either situation that would require a final crew visit to Mir would have the cosmonauts back enroute to Earth aboard their Soyuz capsule before Mir begins automated maneuvers to remove itself from orbit.

A Soyuz craft is pictured docked to the Mir space station during the Shuttle-Mir program. Photo: NASA

"Theoretically we could undock the Soyuz during the final maneuver for some adventure seekers, however it is unsafe, and we are not considering it," an RKK Energia official told Spaceflight Now.

Mir's suicidal plunge will begin with a series of engine burns from the station's core module and conclude with a firing of the main engine of the Progress cargo ship. The deorbit maneuvers are to take place when the station is about 200 kilometers above the Atlantic Ocean off the west coast of Africa.

Once the steering maneuvers are completed, Mir will fall through the atmosphere and incinerate. Several large chunks of debris, however, are expected to survive the cremation and splash down in the Pacific Ocean east of Australia.

Mir is scheduled to be driven from space on February 27 or 28, but the exact timing of its demise will depend on Earth's atmospheric conditions. The station is currently circling Earth in a 326- by 352-kilometer orbit.