WASHINGTON: Space shuttle Discovery's mission will be extended by a day so astronauts can perform an additional spacewalk to remove gap fillers between the craft's heat protective tiles, said a NASA official.
NASA wants to study how far the fillers protrude from the shuttle surface, although it was believed to be minimal based on photographs, flight director Tony Ceccacci told reporters at mission control in Houston on Friday.
Discovery and its crew had been scheduled for a 12-day journey that began on Tuesday. The trip has already delivered German astronaut Thomas Reiter to the International Space Station (ISS), where Discovery docked on Thursday.
The spacewalks will also be used to check suspicious marks on the shuttle nose that officials believe may just be bird droppings. Ceccacci said NASA wants to ensure it is not damage to the tiles.
Discovery will now remain docked with the ISS until July 15 and return to Cape Canaveral, Florida, on July 17.
The shuttle fleets' heat shielding tiles have been a major focus of the missions to space since the 2003 Columbia disaster was blamed on damaged tiles that caused the craft to disintegrate while re-entering the atmosphere.
NASA has since introduced new safety procedures that include orbital inspections of the shuttle surface to ensure the tiles are not damaged by foam debris that falls from the exterior fuel tanks during takeoff.
Reiter's arrival at ISS marks the first time since Columbia that the station has been occupied by three astronauts. The shuttle crew will also assist with much needed repairs to the station orbiting 400 km above the earth.
The shuttle awoke on Friday to the Beatles song "Good Day Sunshine." NASA typically beams music up to space to start the astronauts' workday.
Reiter, 48, was warmly greeted by US astronaut Jeffrey Williams and Russian cosmonaut Pavel Vinogradov, who also gave the German astronaut a hug and kisses on both cheeks. The three men will spend the next half-year working together aboard the station.
Before docking, Discovery flipped over at a distance of just 182 metres below the ISS so the shuttle's underbelly could be photographed by the space station crew to check for any damage to the tiles.
Vinogradov and Williams took 350 pictures of Discovery during the orbital manoeuvre that were transmitted back to earth.
"We saw nothing out of the ordinary," Williams said in an interview.