Astronauts worked Sunday to give NASA a closer look at a troubling gouge on the Endeavour's protective heat shield to help determine whether they need to repair the 3-inch (7.6-centimeter) wound on the space shuttle's belly. Astronaut Charles Hobaugh used the international station's robotic arm to pull a 50-foot (15-meter) laser-tipped boom from Endeavour's cargo bay and hand it off to the shuttle's robotic arm. Then teacher-turned-astronaut Barbara Morgan and crewmate Tracy Caldwell gingerly maneuvered the shuttle's robotic arm to scan the damage in the difficult-to-reach belly area. The laser will send three-dimensional images of the gash to engineers on the ground so they can determine how deep the gouge is and whether repairs are needed. The space agency planned to spend several hours on the detailed inspection of the 3Â½-by-2-inch (9-by-5-centimeter) gash. It was caused by a piece of foam that came off the shuttle's external fuel tank during liftoff last week, striking tiles that insulate the ship from the intense heat of re-entry to Earth, NASA said. The space agency will not know how serious the ding is or whether astronauts need to repair the damage during a spacewalk until it is examined.