Technicians Monday replaced two faulty fuel system parts aboard space shuttle Atlantis, and NASA hoped to be able to reschedule the once-aborted launch attempt for as early as Thursday.
Space agency spokeswoman Lisa Malone said a new pump and 4-inch fuel line were installed and were being prepared for pressure, leak and other checks."The work is going very well," she said Monday.
Shuttle managers scheduled a meeting Monday afternoon to consider a new launch date. Earlier they had said the earliest possible liftoff date was Friday, but with the work progressing smoothly they said a Thursday afternoon liftoff was a possibility.
Because of the shifting positions of Earth and Venus, there is only a 32-day launch opportunity for sending the $550 million Magellan spacecraft in Atlantis' cargo bay toward Venus.
If the shuttle can't get off the ground by May 28, the mission would have to be put off for two years, at a cost of $100 million, until the two planets are again aligned properly.
The launch was scrubbed Friday just 31 seconds before the planned liftoff when controllers noted a sudden power surge on a fuel pump that recirculates liquid hydrogen propellant for one of the three main engines.
Engineers later discovered a tiny leak in a 4-inch-diameter fuel line that carries hydrogen from the external fuel tank to the shuttle.
Had the countdown continued, a computer designed to detect such problems would have stopped the engines from firing and the five astronauts would have been safe, according to the National Aeronautics and Space Administration.
Workers erected scaffolding and platforms around Atlantis on Sunday, removed access panels and unhooked, insulation, wiring and other equipment as they began removing the bad parts.
Two of the astronauts, commander David Walker and pilot Ronald Grabe, practiced shuttle landings in a training aircraft Sunday and then flew to their home base in Houston. Mission specialists Mary Cleave, Mark Lee and Norman Thagard returned to Houston on Saturday.