Washington  - The final solar panel at the space station began unfurling, as planned, on Friday, the final event in the years- long expansion of the energy capacity of the orbiter.

The panel, installed Thursday during a spacewalk by astronauts from the Discovery shuttle, started unfolding at 1506 GMT.

"Everything looking good so far," said a NASA official in Houston in the live webcast on NASA TV. She said the process would take some time, and be halted midway to allow the device to "warm in the sun" - necessary to avoid sticking.

Discovery shuttle docked at the International Space Station earlier this week.

The 300-million-dollar panel is part of a truss segment that will complete the backbone of the station and double its energy capacity, allowing the resident crew size to double to six astronauts.

When the truss is unfurled, it will extend 80 metres, tip to tip, NASA said, doubling the electricity available for science operations on board the station.

All told, the four arrays installed over recent missions will generate up to 120 kilowatts of usable electricity, enough to power about 42 homes of 260 square metres each. (dpa)