The costly exercise requires the utmost precision to ensure that the aging space vehicle is nudged into the right trajectory so that most of it vaporises and the rest splashes down harmlessly in the Pacific Ocean.

The last crew is expected to leave in early summer, allowing scientists to plot the final stages of its descent into the atmosphere with the help of progress cargo ships docked to Mir.

The unmanned transport craft have been the main supply vehicles for the cosmonauts manning the 33-metre-long space complex during its 13-year life span.

They will be used to push the 120-ton Mir down from its present altitude of 400 km above earth to 130 kilometres, before it burns up in the atmosphere in December 1999. One of the cargo ships is already docked to the orbital complex. It will be joined by anotherone in September in preparation for the gradual descent.