About an hour after their Soyuz TM-26 rocket locked on to Mir, which has been running on half power since it was involved in a collision two months ago,the new arrivals went through the hatch to an ecstatic welcome from the two Russians and the American waiting for them on board the station.
Vladimir Solovyov, the flight director said Soyuz had to dock manually because the automatic system had developed a fault. "It was a technical malfunction. The situation was not critical but we will look into it," he said.
The outgoing crew, Vasily Tsibliyev and Alexander Lazutkin of Russia, and the British-born US physicist, Michael Foale, had some bad news for the relief team, however. They had failed to repair Mir's oxygen-generating system, which broke down earlier this week, because they lacked a spare part.
All five spacemen will be able to breathe, as they have back-up canisters with enough oxygen for two months. But fixing the generator will be an added headache for the repair men, who also have to overcome the consequences of the crash on 25 June.
It was the worst accident on the 11-year-old station, which has suffered a string of technical failures because it has outlived its service life, originally intended to be no more than five years. During a manual docking operation, a Progress cargo rocket bumped into Mir's scientific module, Spektr, rupturing it so that it had to be dis- connected from the rest of the station. The task of the repair men will be to seal the hole and reconnect Spektr to the mother craft, which they will start to do on 20 August.
The job will be not only tricky but dangerous. Because Spektr is airless, the cosmonaut who enters it will have to wear a full space suit as if he were on a space walk. The passage into Spektr is extremely narrow and debris may be floating around inside. A puncture in the suit would be fatal.
Commander Solovyov, at 49 a veteran with four missions and 456 days in space under his belt, will do the repairs while his flight engineer, Mr Vinogradov, will stand behind him, shining a torch. Mr Vinogradov, on his first trip into space, was reported to have had a higher than normal pulse rate because of nerves during lift-off from the Baikonur launch pad on Tuesday but officials say he is settling down.
The latest mission is seen as crucial to the whole future of the Russian space programme. Moscow is hoping to exploit Mir for another two years. The United States is supporting Russia despite the mishaps because the two former rivals plan to have a joint space station, called Alpha, by 2003.
However, the US space agency, Nasa, is reserving judgement about whether another US astronaut should replace Mr Foale when an Atlantis shuttle comes to pick him up from Mir next month.