Simulation tests showed the damage could have been substantial

The patch-up procedure is just one of several requirements put on the US space agency before it can launch the Atlantis orbiter next September.

A return-to-flight taskforce says a repair kit for a wing's leading edge is proving very difficult to develop.

But it expects engineers to come forward with several options by March.

A suitcase-sized piece of insulation foam is thought to have hit Columbia's reinforced carbon-carbon wing panels 81 seconds after launch, blowing an opening that may have been 40 centimetres or more across.

In depth guide: Columbia's last mission

Taskforce member Joseph Cuzzupoli, an aerospace executive and former astronaut, said agency engineers were working on three repair proposals.

"I believe it will happen around the March time period that we'll be able to get a better, clearer feeling for where they're going. They're working very hard," he told reporters at a Johnson Space Center briefing.

The leading candidate for the carbon repair kit seems to be a sort of wrap.

The US space agency plans to embed high-tech sensors in the wings of the three remaining space shuttles to detect any blows from debris.

The sensors will determine whether the leading edges of the wings have been hit, but not the degree of any damage, said Cuzzupoli.

The extent of damage would still have to be determined by an inspection by astronauts in orbit, using an extension boom equipped with cameras and lasers.

A tentative launch date for the shuttle Atlantis has been set for 12 September.

The mission will be commanded by Eileen Collins. Much of the flight will focus on testing new safety procedures.