"It is still much too soon to predict either the success of implementation (of a plan to return to space) or the timing of the next flight," members of the Return-to-Flight Task Group wrote in an evaluation released Tuesday.

The National Aeronautics and Space Administration's progress in implementing reforms proposed by the Columbia Accident Investigation Board (CAIB) has been uneven, the task group wrote.

Seven astronauts died when the Columbia shuttle disintegrated over Texas on its way back to earth on February 1, 2003.

Investigators drew a list of errors that caused the accident and proposed changes to avoid future tragedies.

NASA hopes to resume space mission by September, after implementing all of the recommendations.

"Several of the technical responses to specific recommendations have made substantial progress, although none have been completed," the task group wrote.

The group added, "While the tone of this interim report is justifiably positive, progress should not be mistaken for accomplishment. As time passes and the interval before the next scheduled flight diminishes, the enormity of the remaining task looms."

Last week, President George W. Bush announced a plan to replace the shuttle fleet in 2010 with a new shuttle that can take astronauts to the moon, where Bush wants to establish a permanent base by 2015.

SPACE.WIRE