Cosmonaut Sergei Avdeyev, currently on board the Mir space station, has become the person with the longest total stay in space. He has clocked up 681 days.

The 43-year-old civilian space engineer went into orbit on 31 August 1998 on a six-month mission.

However, he had to extend his stay in space when his return seat was given to a Slovakian guest-cosmonaut in February 1999.

The Slovakian cosmonaut was flown to Mir partly to help reduce Russia's debts to Slovakia.

Avdeyev has completed two previous six-month visits to Mir, so his cumulative space experience stands at 681 days on 21 June.

High flyer

Avdeyev is due to return to Earth with his fellow cosmonauts on August 23. By that time, he will not only hold the record for the greatest total time in space but also the second-longest single flight.

He will be only the fourth man in history to have spent over a year in space.

The longest single flight was 14 months. With Mir being abandoned in August this record is in no danger of being broken.

So near, so far

Experts are saying that it is a pity that the current crew have to return to Earth on August 23. This date is determined by the fact that the landing has to be in daylight, as the Russian ground recovery crew can no longer operate at night.

If the crew could stay onboard until September 7 then Mir will have been continuously manned for a decade.

If no money is found to keep Mir in space, then a final crew will arrive in December to try and prepare the space station for its destruction.