Foale and Kalery opened the station's hatch at 00:17 Moscow time, said the head of Russian mission control center's press service Valery Lyndin.

During over five and a half hours of spacewalk, the two astronauts are due to attach two human-imitating mannequins, the European-made "Mister Rando" and the Russian-made "Matryoshka-R" to the ISS's Zvezda module.

The mannequins would allow "scientists to collect information on the doses of radiation humans are exposed to over a long-term space flight," medical experts said earlier.

Foale and Kalery would also set up a laser-based homing system for the European Space Agency (ESA)'s cargo craft, due to be sent to the ISS next year.

The two astronauts are also scheduled to disconnect old panels for Russian and Japanese experiments held on board the ISS and connect new ones.

This would be the first spacewalk held since the US space shuttle Columbia disaster in February 2003 which claimed the lives of seven astronauts and left Russia the sole supplier of the station.

SPACE.WIRE