NASA managers unanimously picked Aug. 27 for the first attempt to launch the space shuttle Atlantis on a mission to resume construction of the international space station - but two precariously attached bolts securing a crucial antenna could delay those plans. Engineers suspect that two of the bolts are too short on the KU-band antenna, which transmits images and other essential data between the space shuttle and Mission Control. They want to make sure the bolts are secure enough so that the antenna does not fly off while in the payload bay during a launch, which could cause catastrophic damage. "We're not going to fly if we think there's a possibility the antenna will come off," said NASA Administrator Michael Griffin on Wednesday. Atlantis has flown with those bolts without trouble since they were first installed two decades ago. The problem was discovered last week, after Atlantis was rolled to the launch pad, when a review of paperwork on bolts on NASA's three space shuttles was ordered because a related problem was found in Discovery. NASA officials likely will not decide until this weekend whether to leave the bolts in place or change them in a tricky swap-out at the launch pad. Technicians would have to build scaffolding on top of a platform six stories off the ground in order to change out the bolts with the shuttle vertical on the launch pad. A swap-out probably would take NASA the two spare days it has in the schedule.