The "burial ship" will fire its engines twice on Friday for about 20 minutes. The first burn will take place at about 0030 GMT; the second will occur at about 0200 GMT. These will slow the station and change its orbit from circular to elliptical.
Ground controllers say all of Mir's systems are working and the ageing station's rotation has been halted in preparation for the catastrophic descent. The platform has even been manoeuvred to allow its solar panels to pick up maximum energy from the Sun.
"The station is under control," Moscow mission control chief Vladimir Solovyov said. "We have begun the irreversible operation."
'Burial ship'
Mir will be pushed into destruction by the Progress supply ship docked to it.
The "burial ship" will fire its engines twice on Friday for about 20 minutes. The first burn will take place at about 0030 GMT; the second will occur at about 0200 GMT. These will slow the station and change its orbit from circular to elliptical.
Then, at around 0500 GMT, the Progress engines will fire one last time to send the station hurtling into the ocean somewhere between New Zealand and Chile.
The splashdown footprint centres roughly around 44 degrees south latitude and 150 degrees west longitude.
Endangered vessels
Most of Mir should burn up in the atmosphere but up to 25 tonnes of debris - some fragments will be as large as a car - are expected to rain down on the Pacific for several minutes.
Five international flights due to pass over the splashdown area at the critical time have been delayed.
But more than 20 fishing boats are known to be in the danger zone. A small number of merchant ships are also travelling through the area.
All the vessels have been warned they are risking their safety and have been advised by the New Zealand authorities to move out of the way.
Mir replacement
As Russia prepared to say goodbye to its space station, the country's Deputy Prime Minister Ilya Klebanov hinted that a Mir-2 could yet be built.
However, he conceded that funds were not currently available to make the project happen. "It is impossible for the next 15 years," Klebanov said.
But Russia's work "on the very serious programmes related to the International Space Station (ISS)" would make it possible to build such a station in the future, Klebanov added.
This would certainly please the many politicians in Moscow who campaigned against the destruction of Mir. Earlier this week, the speaker of Russia's lower house of parliament released a letter sent to President Vladimir Putin urging him to press ahead with a replacement platform.
Gennady Seleznyov told Putin that money received from the Americans for work on the ISS should be directed at a Mir-2 project.