The circular sheet of foil measuring 25 metres in diameter will unfurl from the Progress cargo ship once that has undocked from Mir.

Guided from a distance by cosmonauts aboard Mir, the `mirror' was to begin reflecting sun rays onto Kazakhstan around 1 pm GMT when night will already have fallen on the Central Asian steppe.

In tests lasting six minutes each, the device will light up the Earth with an intensity of between five and 10 times that of a full moon.

The circle of light measuring five to eight kilometres across on the ground will move during the following 24 hours at a speed of about seven metres a second and should be visible at Saratov in the Volga region, Poltova in southern Ukraine, in western Europe, probably Belgium and Germany, then in Canada and inSeattle in the northwestern United States, the Russian ground control centre (TSOUP) said.

However the TSOUP said visibility would depend heavily on the weather and on how the cosmonauts managed to direct the mirror.

The prototype is the second stage of a project called Znamia (flag) thought up by inventor Vladimir Syromyatnikov. If all goes well, the next stage will go ahead in 2000 with the deployment of a similar but bigger reflector, this time measuring 70 metres in diameter.

A giant model 200 metres across is planned in 2003 or 2005, which would be able to light up five big cities.

Syromyatnikov says his invention could not only save money in energy, but could make life easier for people living in the Russian far North during the dark days of winter and might even be used to ``light up whole regions in case of an emergency''.

He said the project posed no threat to the environment because ``it will not significantly modify the temperature on the ground''.

``There is no question of trying todevelop agriculture in these regions,'' he added.

In February 1993, a similar experiment lasting five hours and using a foil circle 20 metres in diameter was carried out. People in western Europe reported seeing `` a queer light,'' Syromyatnikov recalled.

Further in the future, Russian scientists say a giant sheet of foil could even be used to harness solar winds to speed up space flight.

``We could supply scientists with a unique means for a real exploration of the far reaches of the universe and to serve the needs, particularly in difficult times, of our civilisation on Earth,`` Syromyatnikov said on his Internet site.

Viktor Blagov, the deputy head of TSOUP, said Russia had asked foreigners to join in the project but they were not interested.

``We invited foreigners to take part in these tests but they are people with no imagination... the future of our grandchildren is at stake and we cannot convince anyone,'' he said.

In Russia, despite the country's economic woes, ``people like to look up atthe stars,'' Syromyatnikov said.