HOUSTON – A hazardous chunk of foam insulation that broke off space shuttle Discovery’s external fuel tank during launch came from an area where workers made repairs before flight.

Prior to shipping the tank to Kennedy Space Center in March, technicians at the Michoud Assembly Facility in New Orleans sanded down part of a foam ramp to remove a fingertip-sized indentation. That area is on the same part of the ramp where a 0.9-pound chunk came loose about two minutes after liftoff on July 26.

“This is one of many things we are looking at,” said Martin Jensen, a spokesman at NASA’s Marshall Space Flight Center in Huntsville, Ala. “We are encouraging everyone on our team not to jump to any conclusions.”

The piece of foam, a hat-shaped object measuring almost three feet across at its widest point, broke free from the middle of a ramp on the tank’s midsection. The ramp is designed to protect a tray of cables and a fuel line from aerodynamic stress during launch.

A video camera on the tank captured images of the foam streaking past Discovery’s wing. Photos of the empty tank’s jettison in space, taken by astronauts and a camera in the shuttle’s belly, confirmed where the piece originated.

The same location was the site of a so-called “sand and blend” repair by foam workers. During this procedure, a dye absorbed by damaged foam is poured into the blemish. The surface then is sanded down until the dye is gone.

The ramp repair can clearly be seen in “closeout” photos taken of the tank before launch as an area where the newly exposed foam is slightly lighter in color. This type of repair is a common practice.

Questions remain about why foam in that area broke loose, while other spots that underwent the same process did not shed debris. A “tiger team” of investigators is looking into a variety of possibilities, including whether a larger part of the ramp was crushed when the small indentation was made.

“When it comes to the tiger team’s investigation, every avenue is being explored,” said Marion Lanasa, a spokesman for tank contractor Lockheed Martin.

The piece of foam from the ramp was the largest of several to fall from the tank. After a foam strike during launch caused the 2003 Columbia accident, NASA made eliminating hazardous debris the shuttle program’s top priority for safely returning to flight.

The foam issue must be resolved before the next shuttle mission aboard Atlantis is allowed to proceed. NASA managers announced Friday that liftoff of that flight would occur no earlier than Sept. 22. The launch window closes three days later on Sept. 25.

In orbit Friday, the Discovery crew started getting ready to leave the space station by using the outpost’s robot arm to hoist a large canister filled with trash and unneeded equipment into the shuttle’s cargo bay. The canister, which had ferried much-needed supplies to the outpost, was secured for the ride home.

If all goes as planned, the seven astronauts are scheduled to undock from the station early Saturday morning. Pilot Jim Kelly will take the shuttle on a fly around of the outpost before Discovery pulls out of sight, giving the astronauts a chance to take pictures of the station.

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