CAPE CANAVERAL, Fla. (AP) _ A NASA engineer who spied a 4-inch pin wedged against space shuttle Discovery's fuel tank will get a medal for quite possibly saving the lives of seven astronauts who are now en route to the international space station.

Jorge Rivera, 43, was a reluctant hero Thursday, saying he was just doing his job of the past 19 years.

He spotted the pin shortly before the shuttle was supposed to lift off Tuesday night. The launch was scrubbed, the pin was removed, and Discovery finally blasted off Wednesday night on NASA's 100th shuttle flight.

Rivera said ``God only knows what could have happened'' if he hadn't seen the pin and it had ricocheted into an engine at liftoff.

On Thursday, meanwhile, Discovery gained on the space station with each lap of the Earth in a high-speed chase set to end with a docking on Friday.

Discovery's astronauts may have to attempt the rendezvous without the use of the main shuttle antenna. The dish-shaped antenna abruptly stopped working Thursday; it is needed to beam down TV images from Discovery and doubles as a radar tool.

Flight director Chuck Shaw said the problem will not interfere with the docking because the shuttle pilots have backup methods of navigation. But he said it could mean only minimal TV footage for the duration of the flight, which will include four spacewalks to hook up space station parts.

NASA halted Tuesday's countdown after Rivera spotted the pin with binoculars from 50 feet away. The pin had been dropped there by someone, perhaps days or even weeks earlier. Rivera went home, got four hours of sleep and was back at the launch pad long before dawn Wednesday to remove the pin and its attached cord.

Rivera was also responsible for Discovery's first launch delay last week. He was examining film from the previous launch when he noticed that one of the bolts on the external fuel tank was sticking out 2 inches. The bolt should have retracted fully.

NASA called off the Oct. 5 launch attempt to determine whether the bolt malfunction could occur on Discovery and whether it could cause the fuel tank to slam into the shuttle. Engineers concluded that was unlikely.

Because of his back-to-back catches, Rivera was singled out by NASA's boss, Daniel Goldin, following Discovery's safe ride to orbit. The five other members of Rivera's inspection team were also commended.

``I can't manufacture medals overnight,'' Goldin said, ``but we're going to give you the NASA exceptional achievement medal as a team to show that you did the right thing.''

Rivera and the rest of the debris-inspection team are normally looking for any ice on the external tank, which is filled with super-cold fuel. Because of the danger of being so close to explosive fuel, only volunteers are recruited.

The mechanical engineer said his two daughters were thrilled when they heard his name on the news. He said he expects his five older brothers and 10 older sisters to be calling soon from his native Puerto Rico with congratulations.

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