Come in, Valeri and Yelena, your time is up

When the cosmonaut Dr Valeri Poliakov's Soyuz capsule touches down tomorrow, he will be able to breathe fresh air and experience the tug of normal gravity for the first time since he blasted off from Kazakhstan on 8 January 1994. Poliakov has clocked up a space endurance record of 438 days, smashing the previous best, also by a Russian, by almost three months.

The returning hero cannot claim all the headlines: seated alongside him will be the flight engineer Yelena Kondakova, new holder of the female world record for time in space. Kondakova's six-month odyssey paves the way for female researchers to live alongside men on the international Alpha space station, planned for the end of the decade.

For 52-year-old Poliakov, long-term space travel is far from novel: he spent 241 days on board the Mir space station in 1988-89. His latest exploits will result in an accumulated total of almost 23 months, another record. Yet his nomination for the mission was not without controversy. The other candidate for the mission, the medical researcher German Arzamazov, was removed from the stand-by crew after he objected to Poliakov's selection, arguing that his senior's medical skills had become rusty after spending recent years in a desk job, as deputy director of the Moscow Institute for Biomedical Problems.

Kondakova, a 37-year-old aerospace engineer who was a space novice, has also overcome obstacles in her career in cosmonautics. Since Valentina Tereshkova became the first woman to fly in space, in 1963, only one other Russian woman has been chosen to orbit the planet. Kondakova has faced not only the general opposition of the male-dominated space hierarchy, but also the particular opposition of her husband, the veteran cosmonaut and flight director Valeri Ryumin. Kondakova has regaled the press with stories of how she had to squeeze her training between driving their eight- year-old daughter to and from school and arriving home in time to prepare an evening meal for her husband.

Neither has the duo's time aloft been without incident. Poliakov's arrival at Mir was marked by a potentially disastrous collision between his Soyuz ferry craft and the Mir station. His odyssey was almost terminated prematurely last August when a Progress cargo ship carrying supplies and equipment twice failed to dock with Mir, only succeeding at the third, last-gasp attempt.

Kondakova's arrival in October was equally hair-raising, as her Soyuz craft began to sway from side to side and the docking was only saved by Alexander Viktorenko, the crew commander, and Kondakova executing a manual link-up. A few days later, the nine-year-old space station had a power cut, as a short circuit caused its solar panel to turn away from the sun. Equipment required to cleanse the cabin air were temporarily out of action and experiments ground to a halt. This was followed, on 15 October, by a fire in an oxygen generator, which Poliakov smothered with an item of clothing.

These incidents apart, much of Poliakov's time was spent monitoring the changes in his own physical and psychological condition and that of visiting crews. Medical specialists believe his experience will provide valuable insights into the long-term effects of living in zero gravity, such as loss of red blood corpuscles and body fluid, a temporary increase in height, and pulse rate variability (one cosmonaut was brought home early with an irregular pulse).

The most noticeable of these changes is a deterioration in muscular and skeletal strength, effects which even rigorous exercise cannot overcome. As a result, the cosmonauts will have to be lifted from their capsule when they return to Earth. Over the next month or so, their condition will be carefully monitored as they re-adapt to life an Earth.

The psychological side-effects are less predictable. Some cosmonauts have suffered from irritability, homesickness, tiredness and reluctance to work. One, Yuri Romanenko, was involved in a number of verbal skirmishes with ground control towards the end of his 11 months in orbit. Such episodes seem to have been absent on the current mission. Observers often find that male astronauts and cosmonauts tend to be less aggressive and more considerate in the company of women.

The names of both pioneers will probably remain in the record books for many years. Since American shuttle missions rarely exceed two weeks and flight opportunities for Russian women are rare, it is unlikely that Kondakova's time will be broken until the Alpha station is completed early next century. No year-long flights are scheduled, so Poliakov's marathon will probably remain unbeaten until the world's space powers get together seriously to consider sending people to Mars.