By Irene Mona Klotz
at the Kennedy Space Center, Florida
A top-level oversight board says it sees no major obstacles standing in the way of Nasa's plan to finally launch shuttle Discovery next month.
Discovery should be back out on its pad next week
The orbiter is currently being fitted with a new external tank and will be rolled out to the launch pad next week.
Lift-off is targeted for sometime between July 13 and July 31.
The shuttle has been grounded since the 2003 loss of Columbia and its crew of seven, an accident traced to technical as well as management failures.
It has been a tedious, 28-month marathon to return the shuttle fleet to flight, and the next five weeks will not be an easy run-in.
"Nasa has come a very long way," Dan Crippen, a member of the Return to Flight Task Group, said on Wednesday following a public hearing in Houston.
Still to do
The oversight panel, headed by former astronauts Thomas Stafford and Richard Covey, was established to monitor how well the US space agency (Nasa) complied with the recommendations of the Columbia Accident Investigation Board, known by the acronym CAIB.
CAIB laid out 15 directives Nasa needed to fulfil for the safe resumption of shuttle flights. Before Wednesday's meeting, the oversight panel determined that Nasa had met seven requirements.
This week, the space agency won the panel's approval for its implementation of five more CAIB requirements, including a plan to use a complex and never-tested inspection boom to scour the shuttle for damage while it is still in orbit.
Still pending, however, are three of the most critical post-Columbia changes, all of which involve protecting the orbiter and its crew from hazardous debris impacts or mitigating the effects of any impacts - issues that directly relate to the loss of Columbia and its seven crewmembers.
Columbia was downed by a piece of foam insulation that broke off the shuttle's external fuel tank during launch and struck the wing.
The impact tore a hole in heat panels protecting the shuttle's left wing, leaving the ship and its crew vulnerable to tremendous temperatures and pressures during Columbia's re-entry into Earth's atmosphere for landing 16 days later.
Initially, Nasa focused on preventing foam insulation from breaking off the fuel tank, but later realised ice build-ups posed as much of a potential threat. Launch was delayed from May to July to allow time for additional modifications of the shuttle tank to reduce the chance of ice formations.
Nasa managers are scheduled to review those efforts, as well as the results of additional engineering analysis of debris impact threats on 24 June.
After the meeting, the Stafford-Covey task force will reconvene, probably by teleconference, to assess how well Nasa has met the CAIB requirement to eliminate hazardous debris from the shuttle external fuel tank.
It is the task of Covey (l) and Stafford (r) to see that Nasa implements the safety changes
A related issue concerning Nasa efforts to improve the shuttle's ability to withstand debris impacts also will be addressed.
The only CAIB recommendation that seems controversial at this point addresses Nasa's efforts to develop tools and techniques for repairing the shuttle's heat shield in orbit.
In its report, accident investigators wrote that Nasa must have a "practicable" solution for repairing "the widest possible range of damage."
Exactly what those words mean set off a sharp debate during the task force public hearing.
"We've got not only ambiguity in the wording of the recommendation, we've also got apparent dissenting views of some of the CAIB members themselves," Covey said.
"So we naturally have some disagreements about what the real intent was.
"If you take a potential repair technique, what determines at what point it becomes practicable? We have to set the bar before we can evaluate things against the bar," added task force member Jim Adamson, also a former astronaut. "That is the first step."
The debate might be a moot point, as far as Nasa's intent to launch shuttle Discovery goes.
"Having a repair capability is not a constraint to flight by Nasa's plan. They've said that from day one," Adamson said.
The panel intends to complete a preliminary report and present it to the Nasa administrator before Discovery's flight readiness review on 29 and 30 June.