Astronauts John "Danny" Olivas and Christer Fuglesang are preparing for a six-and-a-half-hour spacewalk to install a new 1,700-pound ammonia coolant tank in the International Space Station's solar power truss. A depleted tank, removed during a spacewalk Tuesday, will be mounted in the shuttle Discovery's cargo bay for return to Earth.

Credit: NASA

The spacewalk was scheduled to begin around 5:19 p.m. EDT, but the crew was running ahead of schedule and it could begin earlier. This will be the 132nd spacewalk devoted to station assembly and maintenance since construction began in 1998, the 13th so far this year and the second of three planned by the shuttle Discovery's crew. Olivas will be making his fourth spacewalk while Fuglesang, a Swedish astronaut representing the European Space Agency, will be making his third.

Olivas and Fuglesang spent the night in the station's Quest airlock at a reduced pressure to help purge nitrogen from their bloodstreams. The astronauts were awakened at 12:30 p.m. by a recording of "There is a God" beamed up from mission control from astronaut Patrick Forrester's family.

During a spacewalk Tuesday, Olivas and space station flight engineer Nicole Stott removed a depleted ammonia tank from the left side of the station's power truss and temporarily mounted it on the lab's robot arm. During today's excursion, Olivas and Fuglesang will remove a fresh tank, loaded with 600 pounds of ammonia coolant, from a carrier in Discovery's cargo bay.

Anchored to the end of the station's arm, operated by astronaut Kevin Ford inside the Destiny lab module, Fuglesang will manually hold the 1,700-pound tank during the trip up to the port-one truss segment where he and Olivas will guide it into place, securing it with bolts at top and bottom.

"EVA 2 is completely dedicated to the ammonia tank assembly replacement," Fuglesang said in a NASA interview. "So after the first EVA, the old tank has been put on the station arm. That's kind of where we (are) starting out now. So EVA 2, we both go down to the payload bay. I will jump into the foot restraint in the arm and then get ready to grab this new tank with my arms and Danny will undo the last bolt. And then, while I'm holding this tank, some seventeen hundred pounds, Kevin Ford will fly me with the arm up to the P1 where the old tank was and then I will install the new tank there."

After making electrical connections and hooking up ammonia coolant lines, Olivas will hold onto the depleted tank and the station arm will release it. Ford then will reposition Fuglesang and Olivas will hand him the old tank.

"We put the new tank in place and then we do a little dancing up there such that the old tank, which was held by the arm, it will be now given to Danny in another foot restraint on the truss. He grabs it and then Kevin swings around the arm again such that I can grab the ATA with my arms, the old one now, and Danny lets go. And then we fly back to the payload bay again."

Once back in the cargo bay, Fuglesang and Olivas will lock the old tank in place on the same carrier that held the new tank for launch and attach insulation blankets. Finally, the grapple fixture used to temporarily stow the tank on the station's robot arm will be removed and attached to an ammonia tank on the right side of the power truss that will be replaced next year.

There is a bit of confusion about what the new tank actually weighs. NASA documents show the tank weighs 1,702 pounds but Olivas, in a NASA interview, said he was present when the tank was weighed at the Kennedy Space Center before launch and "it was eighteen hundred and thirty-six pounds."

Regardless of the actual weight, the ammonia tank assembly is the most massive component ever manually handled by space station astronauts.

"That's a lot of mass," Olivas said before launch. "We'll have one attached to the robotic arm but then we're also going to put an EVA crew member on that same robotic arm holding the new Ammonia Tank Assembly. So it's going to be a handful, not only for the robotic arm. Christer Fuglesang is going to be doing a lot of working out in the gym to be able to wrestle with that eighteen hundred pound mass and he'll be the one who's responsible for making sure that that thing stays where it's supposed to go and that it's well behaved."

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision H of the NASA television schedule):

EDT........DD...HH...MM...EVENT

09/03
12:29 PM...05...12...30...Crew wakeup
01:04 PM...05...13...05...EVA-2: 14.7 psi repress/hygiene break
01:54 PM...05...13...55...EVA-2: Airlock depress to 10.2 psi
02:14 PM...05...14...15...EVA-2: Campout EVA preps
02:29 PM...05...14...30...ISS daily planning conference
03:29 PM...05...15...30...MPLM transfers resume
03:44 PM...05...15...45...EVA-2: Spacesuit purge
03:59 PM...05...16...00...EVA-2: Spacesuit prebreathe
04:49 PM...05...16...50...EVA-2: Crew lock depressurization
05:19 PM...05...17...20...EVA-2: Spacesuits to battery power
05:24 PM...05...17...25...EVA-2: Airlock egress
05:39 PM...05...17...40...EVA-2/EV-1: ATA worksite setup
05:39 PM...05...17...40...EVA-2/EV-2: SSRMS setup
06:14 PM...05...18...15...EVA-2: ATA removal from LMC
07:04 PM...05...19...05...EVA-2/EV-1: Prep for ATA install
07:04 PM...05...19...05...EVA-2/EV-2: Maneuver to ATA install
07:34 PM...05...19...35...EVA-2/EV-1: ATA zenith bolts
07:34 PM...05...19...35...EVA-2/EV-2: ATA nadir bolts
07:59 PM...05...20...00...EVA-2/EV-1: NH3/N2 electrical connects
07:59 PM...05...20...00...EVA-2/EV-2: Prep for ATA handoff
08:24 PM...05...20...25...EVA-2/EV-2: ATA handoff, move to LMC
08:44 PM...05...20...45...EVA-2/EV-1: P1 cleanup; ATA handoff
09:54 PM...05...21...55...EVA-2: ATA intall on LMC
11:14 PM...05...23...15...EVA-2: Cleanup and airlock ingress
11:49 PM...05...23...50...EVA-2: Airlock repressurization

09/04
12:04 AM...06...00...05...Spacesuit servicing
01:14 AM...06...01...15...Evening planning conference
01:30 AM...06...01...31...Mission status briefing on NTV
03:29 AM...06...03...30...0ISS crew sleep begins
03:59 AM...06...04...00...STS crew sleep begins
04:00 AM...06...04...01...Daily highlights reel
09:30 AM...06...09...31...Flight director's update
11:59 AM...06...12...00...Crew wakeup

Additional coverage for subscribers:
VIDEO: HIGH DEFINITION DAY 5: SPACEWALKERS CELEBRATE PLAY
VIDEO: HIGH DEFINITION DAY 5: OLIVAS AND STOTT ON EVA NO. 1 PLAY
VIDEO: HIGH DEFINITION DAY 5: COLBERT TREADMILL UNPACKED PLAY
VIDEO: HIGH DEFINITION DAY 5: SPACEWALKERS GET SUITED UP PLAY

VIDEO: HIGH DEFINITION DAY 4: LEONARDO MODULE OPENED PLAY
VIDEO: HIGH DEFINITION DAY 4: MOVING ITEMS FROM SHUTTLE PLAY

VIDEO: WEDNESDAY NIGHT'S MISSION STATUS BRIEFING PLAY
VIDEO: WEDNESDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: FLIGHT DAY 5 HIGHLIGHTS MOVIE PLAY
VIDEO: POST-EVA MISSION STATUS BRIEFING PLAY
VIDEO: SPACEWALKERS PUT THIRD EXPERIMENT IN SHUTTLE PLAY
VIDEO: BRIEFCASE-LIKE PACKAGE RETRIEVED FROM STATION PLAY
VIDEO: EUROPEAN PAYLOAD MOVED FROM STATION TO SHUTTLE PLAY
VIDEO: SPACEWALKERS FREE COOLANT TANK FROM TRUSS PLAY
VIDEO: DANNY OLIVAS DISCONNECTS OLD AMMONIA TANK PLAY
VIDEO: ASTRONAUTS EMERGE FROM AIRLOCK TO START EVA PLAY
VIDEO: OVERVIEW OF FLIGHT DAY 5 ACTIVITIES PLAY
VIDEO: STEP-BY-STEP SUMMARY OF SPACEWALK NO. 1 PLAY
VIDEO: TUESDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: FLIGHT DAY 4 HIGHLIGHTS MOVIE PLAY
VIDEO: MONDAY NIGHT'S MISSION STATUS BRIEFING PLAY
VIDEO: NARRATED OVERVIEW OF THE LEONARDO PAYLOAD PLAY
VIDEO: ASTRONAUTS OPEN UP AND ENTER LEONARDO MODULE PLAY
VIDEO: TIME-LAPSE OF LEONARDO MODULE'S INSTALLATION PLAY
VIDEO: LEONARDO CARGO MODULE ATTACHED TO STATION PLAY
VIDEO: MONDAY'S MISSION MANAGEMENT TEAM UPDATE PLAY
VIDEO: MONDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: HIGH DEFINITION DAY 3: NICOLE STOTT ABOARD STATION PLAY
VIDEO: HIGH DEFINITION DAY 3: UNITING STATION AND SHUTTLE PLAY
VIDEO: HIGH DEFINITION DAY 3: JOIN THE CREW DURING DOCKING PLAY
VIDEO: HIGH DEFINITION DAY 3: LIFE ON RENDEZVOUS DAY PLAY

VIDEO: FLIGHT DAY 3 HIGHLIGHTS MOVIE PLAY
VIDEO: SUNDAY NIGHT'S MISSION STATUS BRIEFING PLAY
VIDEO: SHUTTLE CREW WELCOMED ABOARD STATION PLAY
VIDEO: DOCKING RING RETRACTED TO JOIN TWO CRAFT PLAY
VIDEO: TIME-LAPSE OF DOCKING FROM CENTERLINE PLAY
VIDEO: SHUTTLE FLIES OUT IN FRONT OF STATION PLAY
VIDEO: DISCOVERY PERFORMS 360-DEGREE BACKFLIP PLAY
VIDEO: BEAUTIFUL VIEWS OF DISCOVERY APPROACHING PLAY
VIDEO: TIME-LAPSE VIEW FROM SHUTTLE DOCKING PORT PLAY
VIDEO: STATION CAMERA CATCHES DISCOVERY'S "TI BURN" PLAY
VIDEO: SUNDAY'S MISSION MANAGEMENT TEAM UPDATE PLAY
VIDEO: NARRATED PREVIEW OF RENDEZVOUS AND DOCKING PLAY
VIDEO: THE MOON SINKS BELOW TAIL OF DISCOVERY PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 2 PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 1 PLAY

VIDEO: FLIGHT DAY 2 HIGHLIGHTS MOVIE PLAY
VIDEO: SATURDAY NIGHT'S MISSION STATUS BRIEFING PLAY
VIDEO: NARRATED PREVIEW OF SHUTTLE INSPECTIONS PLAY

VIDEO: LAUNCH REPLAY: INSIDE MISSION CONTROL ROOM PLAY
VIDEO: LAUNCH REPLAY: VAB ROOF 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: 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: PATRICK AIR FORCE BASE PLAY | HI-DEF

VIDEO: POST-LAUNCH BRIEFING PLAY
VIDEO: FLIGHT DAY 1 HIGHLIGHTS MOVIE PLAY
VIDEO: THE FULL LAUNCH EXPERIENCE PLAY
VIDEO: LIFTOFF OF SPACE SHUTTLE DISCOVERY! PLAY | HI-DEF
VIDEO: COMMANDER RICK STURCKOW BOARDS DISCOVERY PLAY
VIDEO: PILOT KEVIN FORD BOARDS SHUTTLE DISCOVERY PLAY
VIDEO: MISSION SPECIALIST PAT FORRESTER BOARDS DISCOVERY PLAY
VIDEO: MISSION SPECIALIST JOSE HERNANDEZ BOARDS SHUTTLE PLAY
VIDEO: MISSION SPECIALIST DANNY OLIVAS BOARDS DISCOVERY PLAY
VIDEO: MISSION SPECIALIST CHRISTER FUGLESANG BOARDS PLAY
VIDEO: MISSION SPECIALIST NICOLE STOTT BOARDS DISCOVERY PLAY
VIDEO: ASTRONAUTS LEAVE CREW QUARTERS BUILDING PLAY | HI-DEF
VIDEO: CREW FINISHES GETTING SUITED UP PLAY | HI-DEF

VIDEO: NARRATED MISSION OVERVIEW MOVIE PLAY | HI-DEF
VIDEO: MEET SHUTTLE DISCOVERY'S ASTRONAUTS PLAY | HI-DEF
VIDEO: NARRATED REVIEW OF SHUTTLE'S PREPARATIONS PLAY | HI-DEF
VIDEO: NARRATED REVIEW OF PAYLOADS' PREPARATIONS PLAY | HI-DEF
VIDEO: THE "COLBERT" TREADMILL PLAY | HI-DEF

VIDEO: MANAGERS EXPLAIN REASON FOR SECOND SCRUB PLAY
VIDEO: WEATHER SCRUBS FIRST COUNTDOWN PLAY | HI-DEF
VIDEO: ASTRONAUTS DEPART QUARTERS FOR PAD 39A PLAY | HI-DEF
VIDEO: CREW GETS SUITED UP FOR LAUNCH ATTEMPT PLAY | HI-DEF
VIDEO: LAUNCH PAD SERVICE GANTRY ROLLED BACK PLAY | HI-DEF

VIDEO: PRE-LAUNCH INTERVIEW WITH RICK STURCKOW PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH KEVIN FORD PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH PAT FORRESTER PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH JOSE HERNANDEZ PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH DANNY OLIVAS PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH CHRISTER FUGLESANG PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH NICOLE STOTT PLAY

VIDEO: AMERICAN AND EUROPEAN PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: THE LAUNCH COUNTDOWN GETS UNDERWAY PLAY
VIDEO: ASTRONAUTS ARRIVE AT THE CAPE FOR LAUNCH PLAY | HI-DEF
VIDEO: FLIGHT READINESS REVIEW SETS LAUNCH DATE PLAY

VIDEO: SHUTTLE AND STATION PROGRAM UPDATE PLAY
VIDEO: THE STS-128 MISSION OVERVIEW BRIEFING PLAY
VIDEO: PREVIEW BRIEFING ON MISSION'S SPACEWALKS PLAY
VIDEO: THE ASTRONAUTS' PRE-FLIGHT NEWS BRIEFING PLAY
VIDEO: SHUTTLE PROGRAM MANAGER EXPLAINS FOAM ISSUES PLAY

VIDEO: PAYLOAD BAY DOORS CLOSED FOR FLIGHT PLAY | HI-DEF
VIDEO: MISSION CARGO LOADED ABOARD DISCOVERY PLAY | HI-DEF

VIDEO: CREW TOURS PAD'S CLEANROOM PLAY | HI-DEF
VIDEO: SHUTTLE EVACUATION PRACTICE PLAY | HI-DEF
VIDEO: ASTRONAUTS BOARD DISCOVERY PLAY | HI-DEF
VIDEO: THE LAUNCH DAY SIMULATION BEGINS PLAY | HI-DEF
VIDEO: PAD BUNKER TRAINING FOR THE CREW PLAY | HI-DEF
VIDEO: CREW BRIEFED ON EMERGENCY PROCEDURES PLAY | HI-DEF
VIDEO: NIGHTTIME APPROACHES IN TRAINING AIRCRAFT PLAY | HI-DEF
VIDEO: TEST-DRIVING EMERGENCY ARMORED TANK PLAY | HI-DEF
VIDEO: INFORMAL CREW NEWS CONFERENCE AT LAUNCH PAD PLAY
VIDEO: ASTRONAUTS ARRIVE FOR PRACTICE COUNTDOWN PLAY

VIDEO: SHUTTLE DISCOVERY ROLLS OUT PAD 39A PLAY | HI-DEF
VIDEO: ORBITER HOISTED FOR MATING TO TANK PLAY | HI-DEF
VIDEO: DISCOVERY MOVED TO ASSEMBLY BUILDING PLAY | HI-DEF
VIDEO: TIME-LAPSE OF DISCOVERY ARRIVING IN VAB PLAY

VIDEO: PAYLOADS DELIVERED TO LAUNCH PAD PLAY | HI-DEF
VIDEO: LEONARDO PUT INTO TRANSPORTER PLAY | HI-DEF
VIDEO: STATION'S NEW AMMONIA TANK PLAY | HI-DEF
VIDEO: MPLM HATCH CLOSED FOR FLIGHT PLAY | HI-DEF
VIDEO: INSIDE SHUTTLE MAIN ENGINE SHOP PLAY | HI-DEF
VIDEO: CREW EQUIPMENT INTERFACE TEST PLAY | HI-DEF
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