NASA says if the launch pad option works, Atlantis should be able to make its planned April 24 liftoff on a 10-day maintenance mission to the International Space Station. But if a rollback is ordered, the launch will be put off at least several weeks. Shuttle Atlantis approaches pad 39A during a Saturday morning rollout on March 25. Freezing the fluid, engineers believe, will prevent air bubbles from forming inside the lines. In addition, the freezing idea means workers would not have to drain any hydraulic fluid from the lines.
Officials say the hydraulic system only can be refilled back in the processing hangar.
Meetings planned for today are aimed at sorting out the pros and cons of the launch pad and hangar options, as well as reviewing the additional analysis conducted since Friday afternoon. Watch our Mission Status Center today for updates as news develops. If the launch pad plan is attempted, the unit swap probably won't start until sometime Wednesday. Officials say it could take 12 hours to remove and replace the PDU, then another day to conduct tests to ensure the new unit is working and the problem has been fixed. Since there are no spare PDUs, the unit aboard shuttle Columbia is being removed for installation into Atlantis.