AN astronaut born in the North-East has played a vital part in ensuring he and the rest of the crew of the Discovery space shuttle make a safe return to earth tomorrow.

Nick Patrick, from Saltburn, east Cleveland, yesterday checked Discovery's heat shield for damage.

Together with shuttle commander Mark Polansky and pilot Bill Oefelein, electronics specialist Dr Patrick used a 50ft extension of the shuttle's robotic arm to inspect Discovery's heat shield for damage from orbiting debris or micro-meteors.

A Nasa spokeswoman said last night the checks were vital to Discovery making a safe re-entry tomorrow. She said: "If they do feel there is concern, they do have ways of fixing it, in orbit."

Crews aboard Discovery and the International Space Station bid one another farewell earlier yesterday, ending eight days of docked operations.

Staying behind on the newly- rewired space station was Discovery flight engineer Sunita Williams.

She swapped places with European Space Agency astronaut Thomas Reiter, who joined Discovery's crew to return to earth after a six-month stay in space.

Expedition commander Mike Lopez-Alegria and flight engineer Mikhail Tyurin rang the ship's bell in Navy fashion and saluted the shuttle and crew as they left.

"From the crew of Discovery, we wish you smooth sailing, thank you for the hard work, and we hope you enjoy the new electrical system on the station," Mr Polansky radioed back.

Mr Oefelein was at the controls as Discovery made a farewell circuit around the space station, giving Discovery's crew a look at their handiwork.

During seven days, 23 hours and 58 minutes of docked operations, the combined crew installed the newest piece of the station's backbone and rewired its power grid during four space walks.