"There is a method for undocking and de-orbiting safely into the southern Pacific Ocean area -- away from any land masses and any population -- a stranded and abandoned orbiter," said James Halsell, a key player in the agency's post-Columbia recovery effort.

In the wake of the Feb. 1 Columbia accident, NASA engineers initiated a study aimed at determining whether astronauts on a crippled shuttle could use the station as a safe haven until a second ship could be launched on a rescue mission.

The study determined the agency could put in place the food, supplies and equipment necessary to sustain as many as seven stranded shuttle astronauts and a two-person station crew for at least 86 days.

"This would allow NASA sufficient time to launch a second shuttle for rescue," the updated NASA plan says.

A severely damaged shuttle linked to the station, however, would have to be undocked from the outpost to make room for the rescue ship, Halsell said.

So engineers set out to determine whether a crippled shuttle could be sent on a fiery plunge back through the atmosphere without endangering populated areas.

Halsell said the engineers determined that minor shuttle computer software changes would be required. The idea then would be to guide the damaged shuttle by remote control to a safe splashdown in a remote area of the south Pacific.

A veteran shuttle pilot and commander, Halsell called the scenario "an extremely unlikely event." But NASA nevertheless decided to take time to go through "a mental and planning exercise" just in case.

With the exception of a planned Hubble Space Telescope servicing mission, all future NASA shuttle flights will be launched to the space station.

NASA consequently deemed it "prudent to examine our options for planning an emergency capability to sustain shuttle crews on the ISS should an orbiter become unfit for (atmospheric) entry," the plan says.

Initially released Sept. 8, the plan largely details NASA efforts to respond to recommendations made by the Columbia Accident Investigation Board.

The agency, however, decided on its own to put in place plans to use the station as a safe haven.

The updated plan, meanwhile, unveiled several new NASA initiatives that are intended to "raise the bar" on shuttle program safety efforts. They include:

Improving the agency's ability to identify, track and resolve problems that crop up with critical shuttle systems.

The initiative is aimed at spotting problems such as the persistent history of launch debris damage that led to the Columbia accident.

A 1.7-pound piece of foam insulation broke free from Columbia's external tank after its Jan. 16 launch and created a fatal breach in the shuttle's left wing. The hole allowed hot gasses to tear the ship apart during an ill-fated atmospheric reentry.

Conducting tests to determine the location and size of shuttle thermal protection system damage that would require inspections and repairs in orbit.

NASA now hopes to launch its first post-Columbia shuttle flight sometime between mid-September and mid-October 2004. But officials acknowledge that the fleet might remain grounded until 2005.

The two most difficult challenges, according to Halsell: Eliminating external tank foam debris and developing techniques to make inspections and repairs in orbit.

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