MOSCOW -- Russian mission controllers in Korolev plan to restart space station Mir's orientation system on Wednesday, March 21, or around 24 hours prior to the complex's scheduled deorbiting, officials said Friday.

Mir. Photo: NASA

With its attitude control up and running, Mir's solar arrays will start tracking the Sun, allowing recharging the station's electrical battaries. The deorbiting maneuvers, which are scheduled to start on early morning Moscow Time March 22, will require reliable supply of energy to the station's computers and propulsion system.

The failure of the station's energy supply system is considered one of the most likely failures, which might hit the mission during the critically important deorbiting operations, said Vladimir Soloviev, the head of Mir operations at mission control in Korolev. The failure of the main computer on Mir is considered the second likely emergency situation.

According to Sloviev, in both scenarios, the flight controllers still will be able to perform a controlled reentry 24 hours later using an autonomous flight control system of the Progress cargo ship.

Currently, Mir is circling Earth slowly spinning in orbit, while its digital control system functions in the so-called "indicator mode," where ground controllers monitor the onboard computer, but do not send any commands to the station's systems.

As of March 16, the average altitude of Mir orbit degraded by some 2.5 kilometers to 236 kilometers from 238.5 kilometers a day earlier.