The crew of Russia's space station has fitted and tested all the equipment necessary for them to leave the craft in late August at the end of what is likely to be its final mission.
Among other systems, they installed and tested a vital back-up navigation system designed to keep the unmanned station from crashing to Earth prematurely in case of a malfunction in the main on-board computer. The backup system can be controlled from the ground and is much more simple and reliable than the existing glitch-prone computer, which failed recently but was restored to operation.
The back-up system does not have to keep Mir's solar panels exactly facing the sun, since the empty station requires only a fraction of the energy it needs now to run life-support systems.