For the second night in a row, a false depressurization alarm woke the Atlantis astronauts and their space station colleagues Friday night, tripping two fire alarms and interrupting a low-pressure protocol being followed by spacewalkers Michael Foreman and Randolph Bresnik.

Foreman and Bresnik were sleeping in the International Space Station's Quest airlock module at a reduced pressure of 10.2 pounds per to help purge nitrogen from their bloodstreams, a routine procedure to help prevent the bends after working in NASA's low-pressure spacesuits.

But the depressurization alarm, apparently the result of an unresolved problem with a new Russian module, triggered automatic procedures that brought the airlock back up to the station's normal pressure of 14.7 psi. Because of time needed to reset various systems, Foreman and Bresnik were told to forego the normal protocol and to sleep wherever they liked, at the station's normal pressure.

In the morning, the spacewalkers will exercise wearing oxygen masks to purge the nitrogen that normally would have been dealt with by a night's sleep at 10.2 psi.

A rapid depressurization alarm Thursday also woke the astronauts. The station's computer system automatically shut down ventilation fans as a precaution and as a result, a fire alarm sounded in the European Space-products in the absence of ventilation.

Engineers later determined the false depressurization alarm was the result of a problem of some sort in the Russian Poisk module, which arrived at the space station earlier this month. The station's air pressure remained normal throughout.

A similar problem developed Friday night when a rapid depressurization alarm sounded at 9:53 p.m. EST. This time around, two fire alarms were triggered, one in Columbus and one in the Quest airlock module.

Because of the interruption and the time that would have been lost re-establishing the 10.2-psi protocol, Foreman and Bresnik were told to sleep where they liked and to plan on an exercise protocol early Saturday, before starting a planned six-and-a-half-hour spacewalk.

Flight controllers agreed to delete a planned "get-ahead" task from the spacewalk timeline and to let the astronauts sleep an extra half hour to make up for the lost sleep. Crew wakeup is now targeted for 3:58 a.m. The spacewalk is scheduled to begin around 8:18 a.m.

Additional coverage for subscribers:
VIDEO: MELVIN AND SATCHER ON MORNING RADIO SHOW PLAY
VIDEO: CBS, NASHVILLE TV AND FOX RADIO INTERVIEWS PLAY

VIDEO: THE FLIGHT DAY 3 HIGHLIGHTS MOVIE PLAY
VIDEO: THURSDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: SPAEWALKERS HAMMER STUCK BRACE ON TRUSS PLAY
VIDEO: MAINTENANCE WORK ON JAPANESE ROBOT ARM PLAY
VIDEO: ENJOYING THE VIEW OF SHUTTLE AND STATION PLAY
VIDEO: REFURBISHED S-BAND ANTENNA INSTALLED PLAY
VIDEO: ASTRONAUTS MOVE ANTENNA FROM SHUTTLE PLAY
VIDEO: SPACEWALK NO. 1 GETS UNDERWAY PLAY
VIDEO: STEP-BY-STEP SUMMARY OF SPACEWALK NO. 1 PLAY
VIDEO: THURSDAY MORNING'S FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: AERIAL LAUNCH AND SRB SPLASHDOWN FOOTAGE PLAY

VIDEO: THE FLIGHT DAY 3 HIGHLIGHTS MOVIE PLAY
VIDEO: WEDNESDAY AFTERNOON'S MANAGEMENT TEAM UPDATE PLAY
VIDEO: SPARE PARTS CARRIER INSTALLED ONTO STATION PLAY
VIDEO: SHUTTLE ARM HANDS PALLET TO STATION'S ARM PLAY
VIDEO: LOGISTICS CARRIER 1 UNBERTHED FROM SHUTTLE PLAY
VIDEO: WEDNESDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: SHUTTLE CREW FLOATS INTO STATION PLAY
VIDEO: ATLANTIS DOCKS TO THE SPACE STATION PLAY
VIDEO: SPACE SHUTTLE PERFORMS 360-DEGREE BACKFLIP PLAY
VIDEO: BEAUTIFUL VIEWS OF ATLANTIS APPROACHING PLAY
VIDEO: SUMMARY OF THE SPARE PARTS PALLETS PLAY
VIDEO: PREVIEW OF PALLET NO. 1 DELIVERY ON FLIGHT DAY 3 PLAY
VIDEO: NARRATED PREVIEW OF RENDEZVOUS AND DOCKING PLAY

VIDEO: THE FLIGHT DAY 2 HIGHLIGHTS MOVIE PLAY
VIDEO: TUESDAY AFTERNOON'S MANAGEMENT TEAM UPDATE PLAY
VIDEO: ROBOT ARM GRAPPLES LOGISTICS CARRIER 1 PLAY
VIDEO: TUESDAY AFTERNOON'S MISSION STATUS BRIEFING PLAY
VIDEO: PREVIEW OF ACTIVITIES ON FLIGHT DAY 2 PLAY
VIDEO: NARRATED TOUR OF THE PAYLOAD BAY PLAY

VIDEO: THE FLIGHT DAY 1 HIGHLIGHTS MOVIE PLAY
VIDEO: LAUNCH REPLAY: INSIDE MISSION CONTROL ROOM PLAY
VIDEO: LAUNCH REPLAYS: EXTERNAL TANK CAMERA PLAY
VIDEO: POST-LAUNCH PRESS CONFERENCE PLAY

VIDEO: CREW FINISHES GETTING SUITED UP PLAY | HI-DEF
VIDEO: ASTRONAUTS LEAVE CREW QUARTERS PLAY | HI-DEF
VIDEO: LIFTOFF OF SPACE SHUTTLE ATLANTIS! PLAY | HI-DEF

VIDEO: LAUNCH REPLAY: PRESS SITE PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD PERIMETER PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: BEACH TRACKER PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD CAEMRA 070 PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD CAEMRA 071 PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: WEST TOWER SITE PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: UCS-23 TRACKER PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PLAYALINDA BEACH PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD FRONT CAMERA PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: VAB ROOF PLAY | HI-DEF

VIDEO: NARRATED REVIEW OF SHUTTLE'S PREPARATIONS HI-DEF
VIDEO: NARRATED REVIEW OF PAYLOADS' PREPARATIONS HI-DEF

VIDEO: STUNNING SUNSET ROLLBACK OF PAD GANTRY PLAY | HI-DEF
VIDEO: A LOOK AT SPACE STATION SCIENCE RESEARCH PLAY
VIDEO: THE STS-129 PRE-LAUNCH PRESS CONFERENCE PLAY
VIDEO: COUNTDOWN PREVIEW AND WEATHER BRIEFING PLAY
VIDEO: ASTRONAUTS ARRIVE FOR LAUNCH PLAY | HI-DEF

VIDEO: NARRATED MISSION OVERVIEW MOVIE PLAY | HI-DEF
VIDEO: MEET SHUTTLE ATLANTIS' ASTRONAUTS PLAY | HI-DEF

VIDEO: ASTRONAUTS TOUR PAD'S CLEANROOM PLAY | HI-DEF
VIDEO: SHUTTLE EVACUATION PRACTICE PLAY | HI-DEF
VIDEO: CREW BOARDS SHUTTLE FOR TEST PLAY | HI-DEF
VIDEO: THE LAUNCH DAY SIMULATION BEGINS PLAY | HI-DEF
VIDEO: CREW ARRIVES FOR PRACTICE COUNTDOWN PLAY | HI-DEF

VIDEO: PAYLOADS DELIVERED TO PAD 39A PLAY | HI-DEF
VIDEO: PLACING PAYLOADS INTO TRANSPORTER PLAY | HI-DEF

VIDEO: FLIGHT READINESS REVIEW SETS LAUNCH DATE PLAY

VIDEO: CREW BRIEFED ON EMERGENCY PROCEDURES PLAY | HI-DEF
VIDEO: TEST-DRIVING EMERGENCY ARMORED TANK PLAY | HI-DEF
VIDEO: CREW ARRIVES AT CAPE FOR TRAINING PLAY | HI-DEF

VIDEO: SHUTTLE AND STATION PROGRAM UPDATE PLAY
VIDEO: THE STS-129 MISSION OVERVIEW BRIEFING PLAY
VIDEO: PREVIEW BRIEFING ON MISSION'S SPACEWALKS PLAY
VIDEO: THE ASTRONAUTS' PRE-FLIGHT NEWS BRIEFING PLAY

VIDEO: SPACE SHUTTLE ROLLOUT IN FAST-FORWARD PLAY | HI-DEF
VIDEO: ATLANTIS TAKES PERCH ATOP PAD 39A PLAY | HI-DEF
VIDEO: ROLLOUT FROM ASSEMBLY BUILDING BEGINS PLAY | HI-DEF
VIDEO: SPACE SHUTTLE ASSEMBLY IN FAST-FORWARD PLAY | HI-DEF
VIDEO: TIME-LAPSE OF ATLANTIS ATTACHED TO FUEL TANK PLAY
VIDEO: ATLANTIS LEAVES HANGAR FOR NEXT LAUNCH PLAY | HI-DEF
VIDEO: TIME-LAPSE OF ATLANTIS ARRIVING IN VAB PLAY
VIDEO: CLOSING ATLANTIS' PAYLOAD BAY DOORS PLAY | HI-DEF
VIDEO: FUEL TANK ATTACHED TO SOLID ROCKETS PLAY | HI-DEF
VIDEO: ASTRONAUTS MAKE A VISIT TO THE CAPE PLAY | HI-DEF
VIDEO: ORBITER DOCKING SYSTEM CHECKED OUT PLAY | HI-DEF
VIDEO: ATLANTIS' FUEL TANK UNLOADED FROM BARGE PLAY | HI-DEF
VIDEO: EXTERNAL TANK ARRIVES AT THE LAUNCH SITE PLAY | HI-DEF
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