BY SPACEFLIGHT NOW

Archive of our coverage of the space shuttle Atlantis' mission to deliver the S0 truss to the International Space Station.

2016 GMT (4:16 p.m. EDT)

The separation maneuver by Atlantis has been performed and the shuttle is now quickly departing the vicinity of the space station.

For those of you scoring at home, here are some numbers from Atlantis' seven-day stay at the station:

• Installed the S0 element adding 26,716 pounds to the ISS
• Transferred 146 pounds of oxygen (130 pounds required)
• Transferred 45 pounds of nitrogen (40 pounds required)
• Transferred 1,463 pounds of water to ISS.
• Estimated 2228.04 pounds of hardware and supplies delivered to ISS
• Transferred 22.9 pounds of spacewalk hardware to ISS
• Estimated 2450.34 pounds of logistics transferred to shuttle
• Disposed of about 229 pounds of condensate from ISS
• Boosted station altitude by about five nautical miles
• Conducted four spacewalks totaling 28 hours and 22 minutes (single-flight record for ISS assembly)

Here is a list of spacewalk actions during Atlantis' mission:

• Total bolt actuations: 289
• TA clamps employed: 92
• Connectors mated or demated: 159
• Connector caps removed or installed: 49
• PIP pins, actuators or latches cycled: 55
• Circuit interrupt device on-off cycles: 12

2012 GMT (4:12 p.m. EDT)

Atlantis has moved above the station again. This is where the separation burn will be performed.

2004 GMT (4:04 p.m. EDT)

Atlantis is now back out in front of the station.

1952 GMT (3:52 p.m. EDT)

The shuttle is now directly below the station.

1939 GMT (3:39 p.m. EDT)

Atlantis has reached a point directly behind the station in terms of the direction of travel of the two spacecraft around the Earth, which is known as the -V bar.

1926 GMT (3:26 p.m. EDT)

Atlantis is reaching a point directly above the space station.

1917 GMT (3:17 p.m. EDT)

Under the control of pilot Steve Frick, Atlantis has begun the lap-and-a-quarter fly-around of the International Space Station so the shuttle astronauts can take photos to document the outpost. The fly-around starts with the shuttle in front of the station, takes Atlantis to a point directly above the complex, then behind it, looping below and back out in front. After climbing above the station for a second time, the final separation engine firing will be performed. This three-foot per second burn will send Atlantis away from the vicinity of the station.

1902 GMT (3:02 p.m. EDT)

The shuttle is now 275 feet in front of the station, continuing to move away.

1839 GMT (2:39 p.m. EDT)

Atlantis is now 75 feet from the station, backing away at about 0.2 feet per second. The shuttle is headed to a point 400 feet away to begin a one-and-a-quarter lap fly around of the station.

1831 GMT (2:31 p.m. EDT)

UNDOCKING! Atlantis is slowing backing away from the International Space Station after a 7-day, 2-hour, 26-minute visit to the outpost that delivered the S0 truss and featured four spacewalks to bring the structure to life.

The shuttle is headed for a 12:26 p.m. EDT landing Friday at Kennedy Space Center. Meanwhile, the station's Expedition Four crew of Yuri Onufrienko, Dan Bursch and Carl Walz have nearly two months left in their six-month voyage in space. In fact, they have a busy schedule over the next few days and weeks.

Early Saturday morning, the station residents will strap into their Soyuz escape capsule and undock around 5:10 a.m. EDT, moving the spacecraft from its current docking port on the Russian Zarya module to a port on the Pirs docking compartment. The re-location will clear the way for the arrival of a fresh Soyuz lifeboat, which is set for launch from Central Asia at 2:26 a.m. EDT on April 25. Docking at the station's Zarya port is expected around 4 a.m. on April 27.

The "taxi crew" flying the new Soyuz to the station will be led by commander Yuri Gidzenko, with Italian astronaut Roberto Vittori and South African space tourist Mark Shuttleworth. The taxi crew will spend a week aboard the station before undocking around 7:05 p.m. on May 4 and returning to Earth aboard the lab's older Soyuz.

The next shuttle mission to the station is scheduled for launch on May 31. Endeavour will ferry the station's next full-time crew to the outpost -- Expedition Five commander Valeri Korzun, flight engineer Sergei Treschev and NASA astronaut Peggy Whitson. Onufrienko, Bursch and Walz will return to Earth aboard Endeavour to wrap up their mission.

1829 GMT (2:29 p.m. EDT)

About two minutes until undocking. The command has been issued to begin driving open the hooks holding Atlantis and station together. Once the hooks and latches are opened, one final command will be sent to undock the shuttle.

The steering jets on Atlantis are inhibited for the period of physical undocking from the station. The separation occurs when large springs push the two craft apart.

1816 GMT (2:16 p.m. EDT)

Now 15 minutes from the scheduled departure of Atlantis from the space station. The undocking is expected to occur 244 miles above the North Atlantic, due west of Ireland.

1805 GMT (2:05 p.m. EDT)

Mission Control has given the Atlantis astronauts a "go" for undocking from the International Space Station at 2:31 p.m. EDT today. The solar arrays on the U.S. and Russian segments of the station have been "feathered" so they are edge-on to Atlantis during undocking. This prevents the shuttle's thruster plumes from damaging the arrays. At this point, the shuttle crew is powering up the Orbiter Docking System to prepare for separation.

1605 GMT (12:05 p.m. EDT)

The hatchway between shuttle Atlantis and the International Space Station was closed at 12:04 p.m. EDT as preparations continue for today's undocking at 2:31 p.m. EDT.

1400 GMT (10:00 a.m. EDT)

The Atlantis astronauts will say their farewells to the three space station crewmembers today and undock from the orbiting laboratory at 2:31 p.m. EDT (1831 GMT) after a successful week-long stay to deliver the S0 truss.

Final hatch closure between the two craft is targeted for 11:29 a.m. See our undocking timeline.

Astronaut Jerry Ross will send the commands to disengage the shuttle-station docking mechanism, allowing powerful springs to gently push Atlantis away. A few moments later, Atlantis pilot Stephen Frick will re-engage the shuttle's steering jets and begin backing straight away to a point about 400 feet in front of the station.

Frick then plans to perform a one-and-a-quarter lap fly around, guiding Atlantis to a point directly overhead before looping around behind the station and below it before returning to the starting point. The shuttle will continue from there back to the point directly overhead, where Frick will fire steering jets to leave the area for good. The separation maneuver is targeted for around 4:15 p.m.

TUESDAY, APRIL 16, 2002

With the completion of the fourth and final spacewalk of Atlantis' mission, NASA managers today declared the new $790 million S0 truss mounted atop the International Space Station fully operational. Read full story.

2107 GMT (5:07 p.m. EDT)

EVA ENDS. Repressurization of the Quest airlock began at 5:06 p.m. EDT to officially conclude the fourth and final spacewalk of Atlantis' mission. Spacewalkers Jerry Ross and Lee Morin spent 6 hours and 37 minutes finishing up some odd jobs, including installation of a spacewalk ladder, lights and shock absorbers.

2000 GMT (4:00 p.m. EDT)

Spacewalker Morin has deployed a spectrometer designed to sniff out ammonia coolant leaks in the completed station truss while Ross has completed installing handrails. They will be relocating some tools before cleaning up and heading back into the airlock over the next hour.

1925 GMT (3:25 p.m. EDT)

Now approaching the five hour mark of today's spacewalk. The astronauts continue to progress through their timeline, performing seemingly routine jobs of installing extra handrails on the S0 truss and tucking thermal blankets away from GPS navigation antennas as the shuttle and station complex orbit 240 miles above Earth.

1735 GMT (1:35 p.m. EDT)

Ross is installing shock absorbers on the Mobile Transporter tracks that run along the newly installed S0 Truss. The absorbers will stop disturbances from affecting the station's robot arm when spacewalkers use transportation carts on the tracks. Earlier the astronauts successfully installed a flood light on the Unity module. They will later install another flood light on the Destiny module.

1617 GMT (12:17 p.m. EDT)

Ross has attached the first flood light to a boom temporarily housed on the S0 truss. The boom will shortly be relocated to the Unity module.

1517 GMT (11:17 a.m. EDT)

The spacewalkers have fitted a 14-foot ladder from the S0 truss to the station's Quest airlock. The so-called "spur" structure will serve as a pathway for future spacewalkers. Lee Morin is now returning to the airlock to retrieve two flood lights that Jerry Ross will install on the Unity node and the Destiny lab.

1500 GMT (11:00 a.m. EDT)

Mission Control reports the latch indicator system checked by Ross has checked out properly. The system will be used when later trusses are attached to S0. The station's truss backbone will ultimately stretch 356 feet in length.

1450 GMT (10:50 a.m. EDT)

Grandfathers Jerry Ross and Lee Morin are getting down to business. Ross, riding on the end of the station's robot arm, is testing the segment-to-segment attach system on the S0 truss by triggering microswitches on the side of the truss to ensure the hardware will work when later sections are launched to the station. Morin is headed up to S0 to work with Ross to install a 14-foot ladder between the truss and airlock. The platform will serve as a shortcut, if you will, to assist future spacewalkers move around the station's exterior.

1445 GMT (10:45 a.m. EDT)

The "Silver Team" spacewalkers are making their way out of the airlock hatch and gathering the tools needed for today's work 240 miles up.

1430 GMT (10:30 a.m. EDT)

EVA BEGINS. The spacesuits of Jerry Ross and Lee Morin switched to internal power at 10:29 a.m. EDT to mark the start of today's space station assembly spacewalk. This is the fourth and final spacewalk of Atlantis' mission. It is Ross' ninth spacewalk and Morin's second. See a timeline of today's spacewalk.

1428 GMT (10:28 a.m. EDT)

Depressurization is now complete and the outer hatch to leading to space has been opened. The start of the spacewalk will marked when the astronauts switch their suits to internal power.

1355 GMT (9:55 a.m. EDT)

Astronauts Jerry Ross and Lee Morin are in the Quest airlock and the inner hatch has been closed. Depressurization has just begun in preparation for today's 6-1/2 hour spacewalk.

TUESDAY, APRIL 16, 2002

The fourth and final spacewalk of this shuttle flight is scheduled to begin around 10:30 a.m. EDT (1430 GMT) today as astronauts Jerry Ross and Lee Morin venture outside the International Space Station to wrap up a variety of odds and ends before Atlantis departs Wednesday.

At the start of the planned 6 1/2 hour excursion, the spacewalkers will pivot a 14-foot ladder away from the S0 truss for attachment to the station's Quest airlock. The so-called "spur" structure will serve as a pathway for future spacewalkers.

They will also install external lights on the U.S. Unity connecting node, test microswitches on the sides of the S0 truss which will be used to confirm the attachment of future truss segments, troubleshoot a balky bolt on a cable cutting system on the Mobile Transporter and tie down a portion of insulation on one of four navigational antennas on the S0.

The transporter completed its first test drive on Monday, driving a total of 72 feet up and down the S0 truss at a speed of one inch per second. Controllers sent manual commands to latch the car in place at 6:40 p.m. EDT. The transporter will remain in that position until the arrival of the Mobile Base System structure on the next shuttle flight in early June.

Expedition Four Flight Engineer Carl Walz sent commands from a laptop computer and the Mobile Transporter moved off of its launch position on the forward face of S0 truss at 8:22 a.m. EDT. The flatcar began its slow trek to an initial worksite 17 feet down a rail which spans the entire 44 feet of the girder.

It took only a half hour to traverse the distance, but sensitive software in the transporter prevented an automatic latching of the railcar to the worksite. Ground controllers accomplished the latching through a methodical series of commands.

Engineers believe that the subtle effects of weightlessness are causing the railcar to "lift" off its tracks by a microscopic distance, thus interfering with magnetic sensors that tell the transporter its position relative to each worksite. The effect is that the sensors are losing contact with magnetic positioning strips on the truss rail, preventing an automatic latching of the transporter. Manual commanding of the latching is working however, and the system is said to be in excellent working order.

The Mobile Transporter software controls about 20 motors, directing it to travel from one point to another, latch itself down to the truss, and plug itself into a power source. The transporter must latch with about three tons of force to insure a stable platform for the eventual mounting of the Canadarm2 robotic arm. On the next shuttle assembly flight to the ISS in June, a platform called the Mobile Base System will be mounted to the transporter upon which Canadarm 2 will eventually be attached so it can travel the length of a football field to support future assembly of station components.

Engineers believe a minor software modification may restore the transporter's ability to automatically latch itself to any worksite. All other transporter systems functioned perfectly throughout its initial test.

MONDAY, APRIL 15, 2002
1945 GMT (3:45 p.m. EDT)

Astronaut Carl Walz restarted rail service aboard the international space station today, sending a $190 million flatcar creeping down the length of the lab's new S0 truss, from one station to another, after tests were interrupted earlier in the day by a subtle glitch. Read full story.

1600 GMT (12:00 p.m. EDT)

From William Harwood:
Engineers at the Johnson Space Center believe the $190 million mobile transporter on the new S0 truss is healthy and operating normally. It appears, however, that an automatic procedure to latch the transporter down at one of two work sites on the truss failed because of erroneous data indicating the cart was not in the correct position. As a result, the software controlling the lock-down process ordered a halt.

Engineers believe the erroneous position data was the result of tiny movements caused by the cart being weightless and floating every so slightly along its rails. That, in turn, caused sensors measuring the cart's location using magnets in its rails to generate data indicating a problem.

Flight controllers are in the process of sending a long series of commands to back out of the automatic lock-down procedure and then to manually latch it in place. If all that goes smoothly, the cart will be unlatched again and the astronauts will be asked to continue their interrupted tests and checkout, sending it to the far end of the S0 truss and, ultimately, back to its starting point at the current work site.

In the meantime, the astronauts plan to hold their traditional in-flight press conference at 12:47 p.m.

1400 GMT (10:00 a.m. EDT)

From William Harwood:
Tests of the space station's new mobile transporter rail car are on indefinite hold while engineers in Houston evaluate what caused its control software to suddenly stop operations during a procedure to latch the flatcar down at a work site. The $190 million transporter successfully moved from its launch position on the S0 truss to a work site 17 feet away on the starboard side of the beam. That's when the glitch occurred.

The transporter ultimately will be used to carry the station's robot arm to various work sites and it must be able to latch itself down to its rails with three tons of force to provide a stable platform for crane operations. As it was going through the latch-down procedure today at work site 4, one of two on the S0 truss, the transporter's control software detected a problem and shut the process down.

Engineers believe the trouble may have started when small magnets used to provide information on the transporter's position on the rails shifted slightly in the weightlessness of space. The astronauts can send commands to manually latch the transporter in place, but engineers want to make sure they fully understand what happened before proceeding. In the meantime, additional tests are on hold and may be off for the day.

"We're basically in a holding pattern, stopped midway latching down," said NASA commentator James Hartsfield in mission control "That's thought to be due to a condition in the automatic mode of the rail car when magnets moved slightly that provided a location indication. As the latches began to close, it just caused the sequence to stop; not a real problem for the transporter, but it would require a manual latching by the crew or by ground control that would then close the latches. Not a systems problem for the transporter, all believed to be in good operating condition on the railway system, but some learning (going on) as the software and automatic operations are used for the fist time in weightlessness."

Engineers may elect to have the crew send commands to remotely latch the transporter in place at work site 4 and then simply leave it there. That's because the equipment needed to attach the Canadarm2 crane to the transporter, scheduled for launch in late May, must be installed at work site 4. That's where the transporter would have ended up today anyway after a normal test run.

1250 GMT (8:50 a.m. EDT)

From William Harwood:
Space station astronaut Carl Walz sent commands to start the lab's flatcar-like mobile transporter, moving it from its launch position on the S0 truss to a work site 20 feet away on the starboard side of the beam. As the transporter was latching itself down at the work site, however, control software suddenly halted the operation and "safed" the $190 million rail car because of a perceived problem of some sort.

Engineers at the Johnson Space Center in Houston are running troubleshooting procedures, but as of this writing it's not known if the transporter has a real problem, whether the glitch can be resolved by adjusting the software's control parameters or whether some other factor might be in play.

Such problems are not uncommon during initial tests of such complex hardware and plenty of time is available today to complete the planned tests. But engineers said a quick fix apparently was not in the cards and the astronauts were told to stand down while additional analyses are carried out.

"It appears this is not going to be a quick answer," astronaut Frederick Sturckow radioed from Houston. "Robo (the robotics officer in mission control) is taking a hard look at all the data and we're going to stand down from MT ops for just the time being and you're free to press on with other activities. We will call you just as soon as we have words on the MT situation."

Read our preview story for details about the mobile transporter tests and operation.

SUNDAY, APRIL 14, 2002

Atlantis astronauts Steve Smith and Rex Walheim performed their second spacewalk of this shuttle visit to the International Space Station on Sunday. The 6 1/2-hour spacewalk rewired the station's Canadian-built robotic arm and readied the complex's newly-delivered rail-car to move. Read full story.

2015 GMT (4:15 p.m. EDT)

EVA ENDS. Repressurization of the International Space Station's Quest airlock is now underway, signaling the end of today's spacewalk at 4:15 p.m. EDT. Spacewalkers Steve Smith and Rex Walheim completed a 6-hour, 27-minute spacewalk to rewire the Canadarm2 to receive power through the new S0 truss. They also released launch restraints that held the Mobile Transporter rail-car in position on the face of S0.

This was the 37th space station assembly spacewalk since construction began in December 1998. Thirty NASA astronauts, one Canadian and five Russian cosmonauts have logged 229 hours and 50 minutes building the international outpost.

2011 GMT (4:11 p.m. EDT)

The hatch is closed.

1948 GMT (3:48 p.m. EDT)

Now six hours into today's spacewalk. Smith and Walheim are making their way back into the Quest airlock.

1915 GMT (3:15 p.m. EDT)

Mission Control just told the spacewalkers it would like to end this EVA on time today. So the airlock ladder installation will be deferred until the fourth spacewalk. And the tool bag relocation will be just tethered to the U.S. Unity node. The spacewalk is nearing the 5 1/2 hour mark. It was scheduled to last 6 1/2 hours. The clean up tasks to put away equipment and return to the airlock become the focus now.

1855 GMT (2:55 p.m. EDT)

The spacewalkers are taking this opportunity to install some circuit-interrupt devices. Installation of circuit breakers were planned on the first spacewalk but were deferred because the EVA was running behind schedule.

1826 GMT (2:26 p.m. EDT)

There are two more jobs left for the spacewalkers today as they continue right on the timeline. Some tools will be relocated on the station's exterior and a 14-foot ladder-like "spur" will be installed between the Quest airlock and S0 truss to help future assembly crews.

1812 GMT (2:12 p.m. EDT)

The second string for Canadarm2 has been powered back up, NASA says, following the rewiring by the spacewalkers. The wiring change was needed to provide power for the arm through S0 truss structure in addition to the Destiny lab. This is in advance of the arm moving to the Mobile Transporter in future assembly missions.

1806 GMT (2:06 p.m. EDT)

The spacewalkers are reattaching the paneling they had removed to make a few more cable connections on the side of Destiny. The second control string on the arm should be powered back up shortly, Mission Control says. The spacewalk continues smoothly today.

1755 GMT (1:55 p.m. EDT)

Another section of paneling on the hull of the Destiny module has been opened as the spacewalkers work on rigid umbilical wiring for Canadarm2.

1742 GMT (1:42 p.m. EDT)

Nearing the four-hour mark of today's spacewalk. The spacewalkers are working to reinstall micrometeorite debris shielding on the Destiny laboratory module. The shielding had to be removed to gain access to wiring for the robotic arm today.

1730 GMT (1:30 p.m. EDT)

Rewiring of Canadarm2's redundant string has been completed, Mission Control says.

1723 GMT (1:23 p.m. EDT)

The spacewalkers are now working together with Canadarm2 wiring.

The Mobile Transporter rail-car launch restraints have been released in advance of tomorrow's checkout. Ground controllers will review the transporter's systems tonight in support of a movement test of the car up and down the S0 truss. The transporter eventually will be used to carry the station's arm to various work sites on the truss to continue its assembly.

"It's very exciting," Smith said in a pre-flight interview on tomorrow's test. "On that day we will have a day off from doing spacewalks, but within the space station, working in concert with the ground controllers, they will actually move the mobile transporter for the first time. And we're all going to be watching from the televisions and from the space shuttle windows at that point.

"But the point is to translate it to certain places on the space station truss. There are actually parking spots on the truss where (the Canadarm2) can stop and plug itself in to receive power and data, those are different stations that it can stop at. So the whole purpose of that task is to make sure that the train works so that the follow-on flights can allow the arm to walk on to that train."

1658 GMT (12:58 p.m. EDT)

Spacewalker Steve Smith has returned to working on attaching connectors to provide power, data and video for the station's Canadarm2 through the S0 truss. Rex Walheim is finishing up releasing the Mobile Transporter launch restraints.

The spacewalk is still on the timeline with no significant problems to report.

1640 GMT (12:40 p.m. EDT)

The primary control "string" for the Canadarm2, which was rewired a short time ago by the spacewalkers, has been powered back up successfully, Mission Control reports. This will clear the spacewalkers to rewire the other "string" a little later in the EVA.

The spacewalkers are still working to release the Mobile Transporter rail-car. Walheim described the job in a pre-flight interview:

"We'll release a lot, a bunch of launch restraint locks. It's all locked in place during launch, obviously, so that the launch vibrations don't shake things loose. And so we have a very complex order of removing bolts or basically loosening them and getting the suspension devices and the drive units of the Mobile Transporter ready to go so that the ground can check it out after we get all these launch locks released."

1618 GMT (12:18 p.m. EDT)

Now 2 1/2 hours into the EVA, the spacewalkers continue their work to release launch restraints that prevent the Mobile Transporter from moving on its tracks along the S0 truss. Once the locks are cleared today, the flatcar will be moved up and down the 44-foot long truss structure during a test tomorrow.

1558 GMT (11:58 a.m. EDT)

The initial round of wiring changes for the Canadarm2 has been completed by the spacewalkers. With that, the ground will now begin power reconfigurations for the robotic arm.

In the meantime, the spacewalkers are now starting work to release locks that have held the Mobile Transporter into place on the face of the S0 truss.

Once they finish this job they will return to rewire the other set of Canadarm2 cabling. Controllers only want to change one "string" of the arm's power system at a time.

1520 GMT (11:20 a.m. EDT)

The spacewalkers are running right on their timeline of activities outside the International Space Station. They are working to reconfigure the power, data and video distribution wiring for the station's Canadian-built robotic arm to run through the S0 truss instead just from the Destiny lab module. This wiring change is necessary so the arm can operate from S0 and the Mobile Base System in the future for use in upcoming station assembly.

As part of the rewiring, the arm's avionics equipment have to be disconnected and reconnected one at a time in a calculated way.

"We really don't want to power down all of Canadarm 2 all at once, we're going to bring it down one redundant string at a time," station lead flight director Bob Castle said. "So we'll power down one string, do the power reconfiguration, power that string up, verify it works, then we'll power down the other string of avionics and chance the power configurations there."

1445 GMT (10:45 a.m. EDT)

Now one hour into today's spacewalk by astronauts Steve Smith and Rex Walheim. The spacewalkers have spent this opening portion of the EVA gathering the tools and equipment needed for their work today.

They then manually released the claw-like clamp of the Lab Cradle Assembly top the Destiny module. This clamp was used to capture the S0 truss during installation last Thursday. But since four strut structures have been installed during the first two spacewalks of this mission, the claw is no longer needed to support or hold S0 in place.

With the claw work completed, the spacewalkers have turned their attention to opening a section of micrometeorite debris shielding on Destiny to gain access to wiring for Canadarm2. This spacewalk will reconfigure the wiring so the arm can be powered through the new mobile transporter on S0, which will allow the arm to travel the length of the ultimate 356-foot long backbone truss of the station in the future.

1348 GMT (9:48 a.m. EDT)

EVA BEGINS. The spacesuits of Steve Smith and Rex Walheim have been switched to internal power at 9:48 a.m. EDT to mark the start of today's space station assembly spacewalk. This is the third spacewalk of Atlantis' mission. Both men performed a spacewalk on Thursday, followed by an excursion yesterday by Jerry Ross and Lee Morin.

In a pre-flight interview, Smith described the objectives of the spacewalk:

"Spacewalk number three will involve the reconfiguration electrically of the space station arm, so it will be largely not usable during that spacewalk," Smith said. "Before we go outside we will park the space station arm, or the Big Arm, so that it's out of the way. Steve Frick, the pilot of Atlantis, will use the space shuttle arm to move me around, so in this case I will be on a robotic arm for the entire spacewalk and Rex will be the free-floater this time, because now he will have experience and I will go to the robotic arm to take his spot there.

"And, we have several tasks to do on that day, largely reconfiguring electrically the space station so that the space station robotic arm can eventually walk on to the S0...truss section. So, we will park that arm early, I will make several connections right at the front of S0 to the United States Lab, then we will go underneath the U.S. Lab and open up a panel there and work on some of the connectors that are there now. The connector configuration there has always been temporary, and we will make it permanent so the space station's arm will have two power strings and have its power available no matter where it is on the space station.

"As you may know, that space station arm can actually walk around the space station with both ends, so we'll provide power for it to be able to do that. So that's the main purpose. While we are letting the ground reconfigure electrically the arm, after we make those connections, we will release several launch restraint bolts that hold the Mobile Transporter, solidly, to the space station truss section during the launch."

We'll update this page periodically with progress reports on the spacewalk.

1335 GMT (9:35 a.m. EDT)

The Quest airlock is being depressurized for an early start of today's spacewalk by Steve Smith and Rex Walheim. This 6 1/2-hour EVA is to rewire the station's robot arm and remove launch retraints on the Mobile Transporter.

SATURDAY, APRIL 13, 2002

NASA's most experienced spacewalker, Jerry Ross, and rookie Lee Morin completed a successful 7 1/2-hour excursion outside the International Space Station today to install the remaining two support struts between the new S0 truss structure and the outpost. Read full story.

2141 GMT (5:41 p.m. EDT)

EVA ENDS. Repressurization of the Quest airlock began at 5:39 p.m. EDT, marking the official end of this successful 7-hour, 30-minute spacewalk by Jerry Ross and Lee Morin. It was the 36th spacewalk performed in support of International Space Station assembly.

The spacewalkers installed the second pair of support struts to structurally mate the S0 truss to the Destiny laboratory, connected a second umbilical to the Mobile Transporter rail-car for the Canadarm2 and removed the keel pins used to hold S0 during launch aboard Atlantis.

The next spacewalk -- by Steve Smith and Rex Walheim -- is scheduled to start at 10:34 a.m. EDT on Sunday. The main goal of the EVA will be to rewire the Canadarm2 to receive power through the S0 truss for future operations with the Mobile Transporter. The robotic arm is currently powered through the Destiny laboratory module.

2135 GMT (5:35 p.m. EDT)

The airlock hatch is now closed and latched.

2133 GMT (5:33 p.m. EDT)

The outer thermal cover on the airlock hatch is not fully closed. So the spacewalkers need to fix that before repressurization.

2124 GMT (5:24 p.m. EDT)

Back inside the Quest airlock, the spacewalkers are preparing to close the hatch.

2120 GMT (5:20 p.m. EDT)

The conclusion of the spacewalk will be timed when repressurization begins.

2102 GMT (5:02 p.m. EDT)

The spacewalkers are now doing some clean up tasks before returning to the airlock to end this EVA.

2058 GMT (4:58 p.m. EDT)

Morin is now securing the V-shaped starboard keel pin in its storage position on the aft wedge of S0.

2052 GMT (4:52 p.m. EDT)

The starboard keel pin had been disconnect from the front side of S0. Morin is carrying it to a stowage location on the truss.

2041 GMT (4:41 p.m. EDT)

Morin and Ross are now getting into position to remove the starboard keel pin.

2034 GMT (4:34 p.m. EDT)

The port keel pin is now being mounted into its new stowed location on the S0 truss. Again, it had to be moved from its original spot used for launch to clear the path of the Mobile Transporter.

2025 GMT (4:25 p.m. EDT)

The Canadian-built robot arm is still maneuvering Morin for stowage of the keel pin on another area of the S0 truss. Ross, meanwhile, is getting some "get-ahead" work done in preps for Sunday's spacewalk by Steve Smith and Rex Walheim.

2005 GMT (4:05 p.m. EDT)

While Morin rides on the Canadarm2 to stow the first keel pin structure, Ross is off to the Z1 truss area to retrieve a foot platform and position it for use during tomorrow's spacewalk. This EVA is nearing six hours in duration at this point. Flight controllers now project the spacewalk will last about 7 hours and 15 minutes today -- 45 minutes longer than planned.

1957 GMT (3:57 p.m. EDT)

The spacewalkers have now unhooked the first of the two V-shaped keel pins, which were used to hold the S0 truss in Atlantis' payload bay for launch. The Mobile Transporter's second umbilical has been fully connected.

1939 GMT (3:39 p.m. EDT)

The redundant Trailing Umbilical System is being connected to the Mobile Transporter on the S0 truss as the spacewalk passes the 5 1/2 hour mark.

Next up will be the removal of the two keel pins.

1916 GMT (3:16 p.m. EDT)

With the two drag links removed and stowed, the spacewalkers are now working together to unreel a ribbon-like cabling called the Trailing Umbilical System for the Mobile Transporter. This is a second and redundant umbilical for the Mobile Transporter, providing a power, data and video link. The first line was installed during the spacewalk on Thursday.

1904 GMT (3:04 p.m. EDT)

Mission Control says the spacewalkers are running about 20 minutes behind the timeline now. Morin is currently relocating the port drag link.

1856 GMT (2:56 p.m. EDT)

The starboard drag link for the keel pin has been stowed. Morin is now working on the port-side one. Ross, meanwhile, is starting preps for installing a redundant trailing umbilical for the Mobile Transporter on S0. The MT is the rail-car that will allow the station's robot arm to travel the length of the truss.

1849 GMT (2:49 p.m. EDT)

With the drag link bar removed from the front of S0, Morin has carried it to the top of the truss where it will be reattached.

1840 GMT (2:40 p.m. EDT)

Both spacewalkers are at work on the front side of the S0 truss removing the keel pins and drag links as the EVA passes the 4 1/2 hour point.

1821 GMT (2:21 p.m. EDT)

In a pre-flight interview, Jerry Ross explained why the keel pins and a device call a drag link have to be removed from the S0 truss.

"There are two large keel pins that are on the forward face of S0, which are there to hold S0 in the payload bay and support it structurally during the launch environment. They're on the forward face, but that's also the face where the (Mobile Transporter's) railroad track is. So we have to remove those keel pins and a drag link, which is a support bar that holds the keel in place for the launch loads."

1811 GMT (2:11 p.m. EDT)

Installation of the port aft support strut for the S0 truss has now been finished. With this fourth and final strut in place, the S0 truss is now completely mated to the International Space Station in the structural sense. Thirty bolts are holding S0 to the Destiny laboratory module.

The spacewalkers, passing the four-hour mark in this EVA, will now work on removing some keel pins from S0 and installing an umbilical for the Mobile Transporter rail-car.

1754 GMT (1:54 p.m. EDT)

With his bolting work completed on the Destiny side of the strut, Ross is installing some thermal covers. Meanwhile, Morin is beginning the tightening of bolts on the third leg's attach point to S0.

1734 GMT (1:34 p.m. EDT)

Bolting of the third leg to S0 is underway.

1728 GMT (1:28 p.m. EDT)

With the strut now bolted to the lab module, Morin is loosing the clamps on the telescoping third leg of the strut, which allows it to reach the attachment plate on S0.

1718 GMT (1:18 p.m. EDT)

Ross has gotten five of six bolts installed to hold the strut to the hull of Destiny, a NASA spokesman said. The last bolt didn't turn all the way in, so it is being backed out and reinstalled.

1714 GMT (1:14 p.m. EDT)

Bolting of the support strut to the Destiny module is underway.

1709 GMT (1:09 p.m. EDT)

Now three hours into today's planned six-and-a-half hour spacewalk.

1706 GMT (1:06 p.m. EDT)

With Morin on the end of the arm by the S0 truss and Ross on the Destiny lab, they are working to swing the support truss into place for attachment.

1645 GMT (12:45 p.m. EDT)

Morin is taking a 20-minute or so trip on the end of the station's robotic arm to get into position to attach the fourth and final support strut for the S0 truss along with Ross.

1629 GMT (12:29 p.m. EDT)

Attachment of the starboard aft support strut from the S0 truss to the U.S. Destiny lab module of the International Space Station has now been completed by Lee Morin.

The strut, along with another to be connected on this spacewalk and two installed on the other side of truss during the mission's first spacewalk two days ago, serve as the structural support for the S0 truss and the subsequent trusses to be launched to the station. All together, the trusses will stretch 356 feet to form the station's backbone for additional power-generating solar arrays and cooling systems. The S0 segment in the central portion of the backbone.

1619 GMT (12:19 p.m. EDT)

Mission Control reports the spacewalkers are progressing right on the timeline. Morin is putting the final touches on the starboard truss -- including tightening clamps and installing thermal covers. Ross is prepping the port truss for its installation, which Morin will assist in once he finishes on the other side.

1610 GMT (12:10 p.m. EDT)

Morin continues finishing up his work on the starboard aft strut. Ross, already done with his tasks, has headed over to the work site to begin releasing the port aft strut for its deployment and upcoming attachment.

1559 GMT (11:59 a.m. EDT)

Having completed his bolt tightening on the Destiny end of the support strut, Ross is putting thermal covers over the strut's foot-plate and fasteners. Morin, meanwhile, continues torquing bolts on his portion of the strut on the S0 truss end.

1546 GMT (11:46 a.m. EDT)

The final tightening of bolts is underway.

1526 GMT (11:26 a.m. EDT)

While Ross is still working on the two-legged bipod portion of the strut, Morin is preparing a third leg for attachment.

"Lee and I will be putting down the large aft struts that attach S0 to the laboratory," Ross said in a pre-flight interview. "The front two struts (installed on first spacewalk) are smaller struts - they only have bipods, two legs on the struts; the ones we have on the back are larger ones, and they have three struts, so they're tripod struts.

"So we'll be putting those two on, which have more bolts on [them], they're beefier, and will be taking more of the loads. So we tell the other guys that we're doing the harder part of the job there!"

1516 GMT (11:16 a.m. EDT)

The spacewalkers continue the bolting work to install their first of two support struts today. Some difficulty has been reported by Ross, but nothing too serious.

1458 GMT (10:58 a.m. EDT)

The starboard aft support strut has been deployed and soft-docked to the lab's hull. It will now be bolted into place.

1453 GMT (10:53 a.m. EDT)

Morin is now assisting Ross in releasing bolts so one of the starboard-side support struts can be swung down for attachment to the Destiny lab.

1445 GMT (10:45 a.m. EDT)

Morin is now standing on a foot-platform installed on the end of the station's Canadarm2. This is platform Morin will work from throughout today's spacewalk.

1433 GMT (10:33 a.m. EDT)

While Morin acclimates himself to walking in space and gets on the end the station's robotic arm for the day's work, Ross (the free-floater today) has made his way to the S0 truss to begin releasing restraints that have held two support struts in place. Once the struts are positioned, Morin will bolt the free ends to the Destiny laboratory module. The two struts, along with two attached during the first spacewalk, provide the permanent structural support for S0.

1411 GMT (10:11 a.m. EDT)

EVA BEGINS. Astronauts Jerry Ross and Lee Morin have switched their suits from station-provided power to internal batteries, which marks the official start time for the spacewalk. The 6 1/2-hour EVA began at 10:09 a.m. EDT. For identification, Ross' spacesuit has broken red dashes around the legs while Morin's has diagonal candy cane stripes.

This is Ross' eighth spacewalk -- more than any other American astronaut. He performed two EVAs to test space station construction techniques on STS-61B in 1985. On STS-37 in 1991 he made one spacewalk to free a stuck antenna boom on the Gamma Ray Observatory and another to test station equipment. And on STS-88 in 1998 he made three spacewalks to connect the U.S. Unity node and Russian Zarya modules during the first International Space Station assembly mission.

Morin is a spaceflight rookie making his first spacewalk today.

"I've been very fortunate to have this opportunity, both to be in space - not to mention being on the International Space Station - and then the icing on the cake is the opportunity to do two EVAs with no less than the king of EVA himself, Jerry," Morin said in a pre-flight interview. "I'm very grateful for that opportunity."

Asked what makes walking in space so enjoyable, Ross said it was "the idea that you're a human being in your own little spacecraft and you're using your own intelligence and your own hands to do things that are so incredible and so important for the future of mankind."

"Add to that the beauty of what you're doing, the incredible sights, a sunrise or a sunset every 45 minutes and the fact that you're going across the surface of the Earth at such a great clip that if you look away for too long, you'll miss entire continents."

The main objectives of this spacewalk are the deployment and attachment the two tripods on the aft side of S0 that will complete its structural link to Destiny, removal of the two large keel pins that helped anchor S0 in the shuttle's payload bay for launch and the installation of a second 'trailing umbilical system' for the Mobile Transporter on S0.

We have posted a timeline of today's activities. You can also see our Spacewalk Statistics page.

Watch this page for periodic updates on the progress of the spacewalkers.

1407 GMT (10:07 a.m. EDT)

The airlock is now at vacuum. The outer hatch leading to space has now been opened. The spacewalk will officially begin with Ross and Morin switch their suits to battery power.

1353 GMT (9:53 a.m. EDT)

Pressure in the airlock is now down to about 3 psi.

1330 GMT (9:30 a.m. EDT)

Depressurization of the Quest airlock is underway this morning for today's spacewalk. Preparations for the EVA have been running ahead of schedule, so the spacewalk start has been moved up by about a half-hour.

SATURDAY, APRIL 13, 2002

NASA's most experienced spacewalker, Jerry Ross, and rookie Lee Morin are set for a 6 1/2-hour excursion outside the International Space Station on Saturday to continue hooking up connections between the new S0 truss structure and the outpost. This second of four spacewalks for Atlantis' mission is due to begin around 10:30 a.m. EDT (1430 GMT).

In a pre-flight interview, Morin gave a detailed overview of the spacewalk:

"Starting off, we will be using the Joint Airlock on the space station; this will not be out of the shuttle airlock, it'll be out of the station airlock. And we will be in the Airlock, and the Airlock is actually, when you have those big EMU suits, the white spacesuits on, you are very confined in that Airlock.

"And it's kind of like, how many students can you get into a phone booth-I mean, it's almost like that; you're really confined in the Airlock, and you're head-to-foot. And so I'll be up at the top of the Airlock, so to speak, the part that opens up into the space station working some controls and valves up there as we finish our transition from being inside the space station to being outside and Jerry will be down, facing the hatch.

"And so finally we'll get to vacuum, and Jerry will open the hatch and there'll be a...when he opens that, that hatch basically looks straight down at the Earth. And so Jerry will go outside, and then after he connects me to the arm and by connecting me I mean I have a reel of wire, which is a safety tether, and so I'm connected inside the Airlock with other tethers, he takes my safety tether and connects it to the end of the arm, and how I'm safety-connected to the arm so I can disconnect my tethers inside the Lab.

"And then I will climb out feet first, and go out and basically feel like I'm climbing through a manhole that is suspended twelve hundred thousand feet over the Earth-and that should be quite a sight. And I'll take some tools and put them on me; I will have a lot on me already but there'll be some others, and we'll move some other supplies out. And then I will shut a thermal cover that goes over that Airlock to keep it warm inside, and then I'll go ahead and do what's called translation adaptation.

"Translation adaptation just gives me a couple of minutes to see what it's like moving around in space as opposed to in the pool, and there's some subtle differences: you don't have the viscosity of the water slowing you down and there's some other subtleties, including having the Earth fly underneath as well as working with a flight-like suit, which is going to be a little stiffer than our training suits which get broken in a little bit differently. So to get five minutes, ten minutes to get that feel and the next thing I'll do is I will climb into the end of the arm.

"Now this arm I'll describe it: if you think about two phone poles connected with a hinge in the middle, and one end of the phone pole is connected to a big swivel joint that's down on the bottom of the Lab, and the other end has a plate, which would be about the size of a trash can lid that's got two ski bindings on it, two water ski bindings on it, and my feet go into those water ski bindings, and then that arm can move wherever (arm operator Ellen Ochoa) decides to take me. And the total length of that is more than sixty feet, so it's a pretty long thing.

"But the first thing that will happen is that Ellen will take me out and turn me around, and bring me right up underneath the back side of S0, and I'll remove some bolts and take a large strut, which will be one leg of a tripod, and I will move that loose leg of the tripod, and the tripod will form and come down and be pointing down at Jerry, who will be down waiting at the Lab to get that, and he'll bolt his end in, and I'll bolt my end in. And the bolts are big 5/8-inch bolts, they're the largest bolts that we have on the station. And I'll be putting those in with a Pistol Grip Tool, which is, basically looks like a, you know, a big power screwdriver and that was actually developed by one of my classmates when he was at Goddard, and so it's exciting to use a tool that one of my friends developed. But that's the tool that we'll use for all of the EVAs to do any tasks involving rotation and tightening bolts.

"Those bolts actually go beyond the capacity of that tool, and so we also use a tool called a torque multiplier, and also a torque wrench, and the torque wrench is very similar to the torque wrench you could buy at a hardware store, and I actually went to the hardware store and bought one and have been playing with that a little bit just to, you know, to have that, to become as familiar as I can with that. And we also have the same tool that we use in training to tighten those bolts and get a, and remember that these bolts are holding together the space station, the truss is from, to the Lab, it's really a crossroads of the station, and so these bolts have to be tightened just the right way, and so this, we do a lot of training in terms of tightening them.

"So after we've gotten those bolts tightened, then we need to do the same thing on the other side. And so what will happen is that Ellen will take the arm, and that arm will have to come all the way out around the station and then fold in on the other side, and that takes about twenty or twenty-five minutes, which is really a, going to be a spectacular ride. And we, Rex (Walheim) nicknamed that the "hiya" maneuver, and so we call it the "hiya" maneuver. And so I'll do this "hiya" maneuver on the end of the arm, and basically the arm comes out almost straight, and I actually will be going right over the rudder of the shuttle.

"And so it'll be a, you know, an amazing view. And I'll have a camera with me - we have some of our Nikon F5 cameras are built with coverings so that you can take them outside and they have special lubricants so that they'll work EVA - and we'll be able to take pictures to document the task. And it also, there's a lot of things about the station from the outside that it's not so easy to get pictures of. And you certainly can get pictures, and we do a flyaround with the shuttle and go all the way around the station twice, and that's an opportunity to take pictures of the space station from the outside, but this is another opportunity on the end of that arm, of being able to look back in at it at fifty, seventy-five, or a hundred feet from some unusual angles that people aren't usually looking at the space station from, and to be able to document some things that the people on the ground want to see about the station.

"Anyway, after we finish the "hiya", I'll come in from the other side and basically do it, another strut. And the, once we have the four struts on, then the truss is, you know, mechanically connected.

"And then we move the arm out and come in from the front and there's a number of other tasks: we will connect some large power cables that go to that MT - the little railroad car-type thing - that has power cables going to it and they are a big, flat cable, they are about an inch-and-a-half wide-and so Jerry will feed that cable to a large reel to me, and then I'll install that; and Rex and Steve will also install a similar one on one of their EVAs.

"And then we remove a number of...it's basically shipping materials that are bolted to the outside of the truss that need to come off, and we need to put those out of the way. So we'll remove a number of, they're called keel pins and drag links, and we will move those off and put those away. And that'll finish up our second EVA."

1820 GMT (2:20 p.m. EDT)

The space station crew provided a glimpse of life in orbit today, describing attempts to toss foam balls the length of the outpost, watching "Alien" DVDs while jogging on their treadmill and the pleasure they all felt on welcoming their first visitors aboard. They also said they were pleased to hear that Barbara Morgan, who served as Christa McAuliffe's backup in the ill-fated "Teacher in Space" program, will finally get a chance to fly. Read full story.

FRIDAY, APRIL 12, 2002

It is a quieter day aboard the International Space Station and shuttle Atlantis today after the hectic day yesterday installing the S0 truss and the subsequent 8-hour spacewalk.

Today will see transfers of experiments and supplies to the station. Also oxygen and nitrogen will be transferred to refill the Quest airlock's high-pressure tanks with the gasses breathed by spacewalkers.

The crew will take a break to talk with reporters from MSNBC, CBS Radio Network and WWJ-TV in Detroit at 12:28 p.m. EDT. At 2 p.m. NASA television will switch to live coverage of NASA Administrator Sean O'Keefe's address on "Pioneering the Future."

After getting two hours of time off during the afternoon, both crews are scheduled to begin their sleep period at 8:44 p.m.

Meanwhile, NASA says the S0 Truss is functioning well after its mounting to the Destiny laboratory module. Today, ground controllers will activate the Global Positioning System and the Rate Gyro Assembly located on S0 that will begin providing navigation and attitude data for the station.

THURSDAY, APRIL 11, 2002

Despite a few bumps along the way, the Atlantis astronauts and their space station colleagues successfully attached a 27,000-pound truss to the orbiting outpost today, accomplishing the primary goal of the 109th shuttle mission. Read full story.

2225 GMT (6:25 p.m. EDT)

The first of four spacewalks of the current mission of shuttle Atlantis is now in the books. Repressurization of the Quest airlock began at 6:24 p.m. EDT, marking the official end of this 7-hour, 48-minute spacewalk by Steve Smith and Rex Walheim.

The duo completed support strut attachments and numerous umbilical connections today between the S0 truss and the International Space Station. S0 was mounted to the Destiny module by the station's robot arm this morning before the spacewalk began.

The next spacewalk -- by Jerry Ross and Lee Morin -- is scheduled to start at 10:34 a.m. EDT on Saturday.

2220 GMT (6:20 p.m. EDT)

The hatch is now confirmed closed and latched. The spacewalk conclusion is marked at airlock repressurization.

2219 GMT (6:19 p.m. EDT)

Smith and Walheim are both now back in the airlock, preparing to close the hatch.

2206 GMT (6:06 p.m. EDT)

The spacewalkers are now doing tool inventories before they seal up the airlock to conclude this EVA. Now passing 7 hours, 30 minutes into the spacewalk.

2153 GMT (5:53 p.m. EDT)

The spacewalkers are finishing up their work now. Lots of congratulations going around between the astronauts and ground controllers. Although the EVA has lasted longer than planned and a couple low-priority jobs have been deferred to another spacewalk, all the main tasks have been performed.

2131 GMT (5:31 p.m. EDT)

Steve Smith has finished his oxygen tank recharge in the airlock and is now joining Rex Walheim to un-reel the so-called trailing umbilical system for the Mobile Transporter on the S0. This is a two-person job. The Mobile Transporter is the first piece in the system that will ultimately allow the Canadarm2 to travel the length of the station's backbone when it is finished.

2115 GMT (5:15 p.m. EDT)

Walheim has about another 10 minutes of connection work to do. Smith has been told to head back to airlock to recharge his spacesuit so the spacewalk can be extended even further. Walheim's suit remains in good shape.

2103 GMT (5:03 p.m. EDT)

Flight controllers say this spacewalk could now run over seven hours in length. It is nearly 6 1/2 hours at this point and cable connections continue. Smith and Walheim still plan to extend the cable reel for the Mobile Transporter on the front of S0. However, installation of a couple of circuit interrupt devices have been slipped to a future spacewalk.

2036 GMT (4:36 p.m. EDT)

Now six hours into this spacewalk. Smith and Walheim are still busy working on various power, data and cooling umbilicals between the S0 truss and the rest of the station. The truss was mounted to the outpost this morning. Other than the difficulty deploying the aft cable tray, the spacewalk has gone very well to this point. But the spacewalkers are a bit behind schedule, prompting flight controllers to discuss the option of delaying some of the remaining tasks to other EVAs on this flight.

2006 GMT (4:06 p.m. EDT)

Mission Control says Walheim should now be working on the port-side umbilical tray installation and connections. Smith continues his work on the aft side of the S0 truss.

1930 GMT (3:30 p.m. EDT)

Spacewalkers Steve Smith and Rex Walheim are approaching the five-hour point in today's EVA. Mission Control says they are running about a half-hour behind the timeline due to the extra work that was needed to get the aft umbilical tray deployed. The spacewalkers have just finished mating what officials referred to as the "critical" umbilicals on the starboard umbilical tray between the station and S0 truss.

1910 GMT (3:10 p.m. EDT)

As the spacewalk continues 240 miles above the Earth, NASA managers on the ground today approved new launch dates for three upcoming shuttle flights.

Shuttle Columbia's 16-day Spacehab research flight of STS-107 slips from July 11 to July 19; the space station assembly flight of Atlantis on STS-112 slips from Aug. 15 to Aug. 22; and the STS-113 station mission of Endeavour moves from Sept. 19 to Oct. 6.

The next shuttle launch remains officially targeted for May 31 when Endeavour will return to the station.

1834 GMT (2:34 p.m. EDT)

Walheim is heading back to resume his work with the starboard umbilical tray, specifically hooking up the cables running on that tray. With the aft tray now deployed, Smith can work on connects on the back side of S0. This spacewalk is nearing the four-hour mark.

1829 GMT (2:29 p.m. EDT)

With some extra effort, the spacewalkers have successfully deployed the aft umbilical tray on the S0 truss.

1816 GMT (2:16 p.m. EDT)

With the starboard umbilical tray attached, Walheim is going to get off the arm and climb to the back side of S0 along with Smith to assist in getting the aft tray to fold down. Smith wasn't able to fully deploy the aft tray by himself earlier.

1755 GMT (1:55 p.m. EDT)

Riding on the end of the station's robotic arm, spacewalker Rex Walheim is now attaching the starboard umbilical tray on the Destiny module. Steve Smith is moving over to assist in this installation job. This tray looks like a long beam. It will be used in the routing of power and data cables between Destiny and S0.

Meannwhile, Smith reported some difficulty deploying the aft tray, which flight controllers are discussing.

1744 GMT (1:44 p.m. EDT)

While Steve Smith works on the aft avionics tray on the back side of S0, Walheim has unbolted one of the umbilical trays from the truss for its deployment along the length of the Destiny lab module. This tray carries a variety of umbilicals to be connected between the newly-installed truss and the station.

1736 GMT (1:36 p.m. EDT)

Now three hours into today's spacewalk.

1656 GMT (12:56 p.m. EDT)

The forward port strut has been bolted, completing this job for the spacewalkers today. The V-shaped bipod struts are the structural link that will keep the truss attached to the station.

The spacewalkers will now focus on electrically connecting the S0 truss to the rest of the space station via several different sets of cables over the next couple of hours.

1650 GMT (12:50 p.m. EDT)

So far so good in this first of four spacewalks of the Atlantis mission. The spacewalkers are currently a bit ahead of the timeline. Work continues on the forward port support strut.

1640 GMT (12:40 p.m. EDT)

Walheim is now working on the second strut. Smith has started preparatory work for the upcoming electrical and data cable connections to S0.

1611 GMT (12:11 p.m. EDT)

The first of four support struts -- the forward starboard strut -- has been installed from the S0 truss to the Destiny laboratory module. These struts are the permanent structural supports for the S0 truss. One more will attached today; the others to be connected later in Atlantis' mission.

1543 GMT (11:43 a.m. EDT)

Spacewalker Rex Walheim is now beginning to bolt the first strut into place.

1534 GMT (11:34 a.m. EDT)

Spacewalker Steve Smith has released restraints to unfold the first strut that will be connected to structurally support the S0 truss to the space station. The spacewalkers have spent the first portion of this EVA getting set up for their work today.

1438 GMT (10:38 a.m. EDT)

EVA BEGINS. Astronauts Steve Smith and Rex Walheim switched their spacesuits to internal battery power at 10:36 a.m. EDT, marking the official start to today's six-hour spacewalk. The two men will float out of the station's Quest airlock shortly.

In a pre-flight interview, Smith gave a detailed overview of the work to be performed during this first of four planned spacewalks of Atlantis' mission:

"Well after we wake up, Rex and I will spend about three hours preparing for the spacewalk, doing this alternative prebreathe protocol approach. In parallel, Ellen Ochoa, our flight engineer, will be using the space station's arm to install S0. And, once that has been completed, we have the "go" to go exit the Airlock, the space station airlock.

"I will go out first and attach myself to the space station, while I'm attached to Rex; once I've attached myself to the space station I will attach Rex to the space station robotic arm, which was just used to install S0. For the remainder of the EVA Rex will be riding the robotic arm, and I will be what's called free-floating-kind of the free player that can move around on the space station just using my hands-and we will begin to physically attach the truss to the space station.

"The first thing we do is attach two struts that are in the front of S0, physically, to the space station, so those are called the forward struts...they have very large, 5/8 inch bolts that will be driven actually into the Lab. Those bolts were driven into the Lab before it left the Earth, so we've made sure that that worked.

"After we physically have attached the truss to the Laboratory then we will electrically attach the truss to the Laboratory. There are two very large, about three hundred pound, umbilical units that are launched on top of the truss. They are not attached, except by bolts, to the truss, they're not attached electrically. So Rex will go up to the top of the truss with the arm, take these two very large umbilicals down to the Lab, place them on top of the Laboratory, so they will attach physically to the Laboratory, then at both ends he will attach electrically the truss element to the Lab.

"So now the electricity will be able to flow through the space station, through the Laboratory, up to the truss section, which of course will then power the Mobile Transporter, etc., and all its computers. That will take the majority of the spacewalk, these two struts and these two very large umbilicals.

"The last thing we will do is supply power to the Mobile Transporter itself. It will use something called the Trailing Umbilical System, or TUS is the abbreviation, and that is a very, very, very large reel of cabling that is currently wound up, and we will release that cabling and string it across the front of the truss to the Mobile Transporter, which is launched on the other side. And that will then provide the capability to send power and commands and data to and from the Mobile Transporter and will help it start to heat itself, for example, because it will have been without power during the flight until then.

"While Rex is completing some of the connections on the forward part of the truss, I will go in the back of that truss, which would face something called Z1 -- that was delivered about a year ago by the 3A crew -- and on the back of the truss is a tray that folds down like this, and it also has connections that go from the truss to the Laboratory. And so I will be working back there to make those connections. When that tray comes down it will meet a tray that was deployed by the Z1 crew, and there are all kinds of cables back there-many, many, many, many cables, all routed among themselves, so we call that the rat's nest, because it looks a little bit like a rat's nest. So when I go work back there you might hear one of us say, "Well, Steve's heading back to the rats' nest to do that."

"So at the end of EVA 1 we should have the truss physically attached to the space station and electrically attached to the space station, in addition to finally providing power to the Mobile Transporter."

1347 GMT (9:47 a.m. EDT)

The Lab Cradle Assembly's claw device has been fully closed, mechanically attaching the 27,000-pound S0 truss to the Destiny laboratory module of the International Space Station at 9:46 a.m. EDT.

S0 forms the central section of the eventual multi-truss backbone of the station that will support more solar arrays and cooling systems for expansion of the outpost's capabilities.

So with the truss mounted to the lab, the attention now turns today's spacewalk by Steve Smith and Rex Walheim. The six-hour excursion is now scheduled to begin around 10:40 a.m. EDT, about 25 minutes earlier than expected because preparations are running ahead of the timeline. The duo will connect two of four support struts between the truss and station, along with and power and computer cables.

1325 GMT (9:25 a.m. EDT)

The first stage of capture by the Lab Cradle Assembly has been completed. The second stage will take another 20 minutes, NASA says.

1319 GMT (9:19 a.m. EDT)

The S0 has been positioned within reach of the Lab Cradle Assembly. Astronaut Lee Morin will command the clamp of the LCA to capture the truss segment.

1309 GMT (9:09 a.m. EDT)

Mission Control reports the truss has just inches left to move. A claw on the Lab Cradle Assembly will then close to capture and hold S0 to the station.

1224 GMT (8:24 a.m. EDT)

The S0 truss is now over the shuttle's crew module as the work to maneuver the structure into the installation position continues using Canadarm2.

1117 GMT (7:17 a.m. EDT)

The station's arm is slowly beginning to maneuver the S0 truss structure out over Atlantis' port wing. The truss will be mounted to the top of Destiny laboratory module, which is above Atlantis' nose.

1050 GMT (6:50 a.m. EDT)

The 27,000-pound S0 truss is now being hoisted out of the shuttle's payload bay by the station's Canadarm 2. Meanwhile, spacewalk preparations are now underway. The spacewalk will start once the truss has been attached to the station about four hours from now.

In a pre-flight interview Atlantis astronaut Ellen Ochoa describes her job of operating the station's arm.

"Well, I've been fortunate enough to fly the shuttle robot arm on my three previous flights, and on this flight I'm moving on to the new station robot arm. And we're using that arm in two main ways: and the first is to actually reach into the shuttle payload bay to unberth the S0 truss and move it around and install it onto the space station, on top of the Lab; and then, we use it during all four of the spacewalks with a crewmember attached to it to move that crewmember around to all the various different worksites that he'll need to get to during the spacewalks."

So why is a shuttle crew member controlling the space station's robotic arm?

"Well, we actually have three people that are trained on the station robot arm, and two of them are already on station right now -- Dan Bursch and Carl Walz -- and I'm the third person. And the reason we've trained people on both the shuttle and the station crew is so that, a lot of the training for this mission, both for the S0 install and for the spacewalks, occurred after Dan and Carl launched into orbit. And while they can do some types of training on orbit, it really helps to be down here on the ground working directly, day-to-day, with the spacewalkers, or with any last minute changes to the install. So I'll have sort of the up-to-date information about all the tasks, whereas Dan and Carl will bring to the table the actual flight experience of using the arm."

1008 GMT (6:08 a.m. EDT)

Atlantis astronaut Ellen Ochoa, assisted by Expedition Four flight engineer Dan Bursch, has grappled the S0 truss riding in Atlantis' payload bay with the space station's Canadian-built robot arm.

Soon the retention latches holding the truss in place will be released, clearing the way for the 44-foot long structure to be lifted out of the bay and maneuvered into position for mounting to the Destiny laboratory module.

A six-hour spacewalk by shuttle astronauts Steve Smith and Rex Walheim to attach support struts and connect cabling is targeted to begin shortly after 11 a.m. EDT today.

WEDNESDAY, APRIL 10, 2002

Shuttle Atlantis reached the International Space Station Wednesday, kicking off a week-long visit by Atlantis to deliver the central section of the station's backbone truss structure. The truss will be mounted to the complex early Thursday, shortly before a six-hour spacewalk begins. Read full story.

See our master flight plan for a look at Thursday's timeline.

1810 GMT (2:10 p.m. EDT)

HATCH OPENING. The astronauts of space shuttle Atlantis and the International Space Station have been united with the opening of hatches between the two spacecraft at 2:08 p.m. EDT. Greetings are underway inside the U.S. Destiny science lab of the station.

1622 GMT (12:22 p.m. EDT)

The docking ring has been retracted and the hooks and latches have engaged to tightly seal the 100-ton shuttle to the 150-ton space station, Mission Control reports. Hatch opening is scheduled for about 2 p.m. EDT.

1614 GMT (12:14 p.m. EDT)

The docking ring is now being retracted.

1606 GMT (12:06 p.m. EDT)

Docking occurred 242 miles over central China, a couple minutes early. Mission Control had projected that docking would be a few minutes late.

1604 GMT (12:04 p.m. EDT)

CONTACT AND CAPTURE! Space shuttle Atlantis has docked to the International Space Station for a week-long visit to deliver the central section of the station's backbone truss structure. The S0 truss will be lifted out of Atlantis' payload bay by the station's Canadian-built robotic arm tomorrow and mounted to the Destiny module.

The motions between the shuttle and station will be damped out over the next few minutes. Later, the hooks and latches will be closed to firmly join the two craft and Atlantis' Orbiter Docking System docking ring will be retracted to form a tight seal.

The opening of hatches between the station and shuttle is expected in about two hours. For the station's resident crew -- Russian commander Yuri Onufrienko and American flight engineers Carl Walz and Dan Bursch -- the Atlantis astronauts are their first visitors since December.

In a pre-flight interview, commander Mike Bloomfield described the busy work day of this Flight Day 3.

"Our Flight Day 3, which is our rendezvous day, is an incredibly busy day. We have the rendezvous that happens in the morning, and we finally dock, and then once we dock we have to open up all of the hatches so we can get to the crew, to the International Space Station, with Dan and Carl and Yuri that are up there.

"And then we have to make a bunch of transfers: we've got to take some of our spacewalking outfits across, there are some other experiments that we've got to take across, and then Ellen (Ochoa) and Dan (Bursch) are the ones that are going to go through this S0 dry run. And basically what they want to do is they want to take the robotic arm, and they want to go through some motions to make sure that it's going to maneuver the way we expect it to maneuver the next day. And what we're really looking at is we're really looking to see if we have the cameras set up the right way, and if we have the infrastructure around Ellen and Dan so that they can do the S0 install in the time that they think they need to do it.

"If you look at, we call it the robotics workstation on the International Space Station, and that's where Ellen and Dan are going to be working from, that's where they're going to be maneuvering the robotic arm: it's enclosed inside the Lab, there's no windows there. And so they have all these camera views and they basically have three screens in front of them, and then we're going to add another two so they'll have five screens altogether, and we'll feed them all these views to make sure that they can maneuver the arm with S0 on it, to the correct position. And so, that's what we're primarily looking for, to see whether or not the cameras are all set up the right way where Ellen and Dan can do this maneuver safely."

1603 GMT (12:03 p.m. EDT)

Now 10 feet to docking.

The orientation-control gyros on the station are disabled for the linkup to keep the complex from moving, while Atlantis' thrusters are programmed to fire in a calculated way to force the two docking ports together at the point of contact.

1603 GMT (12:03 p.m. EDT)

Distance 15 feet.

1602 GMT (12:02 p.m. EDT)

Now 20 feet to docking.

1601 GMT (12:01 p.m. EDT)

The alignment between docking ports on Atlantis and the space station is acceptable and no "fly out" maneuver by the shuttle is necessary. The final approach along the last 30 feet is now in progress.

1558 GMT (11:58 a.m. EDT)

Distance is now 50 feet as Atlantis slowly inches ever closer to the International Space Station under the manual control of commander Mike Bloomfield.

1554 GMT (11:54 a.m. EDT)

The distance separating the shuttle and station is now 80 feet.

1550 GMT (11:50 a.m. EDT)

The shuttle is now inside 110 feet to docking with the space station.

1544 GMT (11:44 a.m. EDT)

Atlantis is now 155 feet from the station, closing at .15 feet per second.

1538 GMT (11:38 a.m. EDT)

Now 215 feet to docking. Atlantis is closing at just under .2 feet per second.

1533 GMT (11:33 a.m. EDT)

Atlantis is now 266 feet directly in front of the International Space Station's docking port, heading for a link up in about a half-hour.

1529 GMT (11:29 a.m. EDT)

Atlantis has now reached the velocity vector, or V-bar, directly in front of the station's direction of travel with a distance just inside 300 feet. The shuttle can hold at this point for a stationkeeping maneuver, if needed, to ensure proper alignment between the two craft before the approach to docking begins.

1526 GMT (11:26 a.m. EDT)

Atlantis has been given a "go" for docking by Mission Control. Also, the solar arrays on the Russian modules have been feathered for the final approach by the shuttle.

1521 GMT (11:21 a.m. EDT)

The shuttle continues its swing from a point below the station to directly in front of the outpost. Distance currently 400 feet.

1516 GMT (11:16 a.m. EDT)

Atlantis has now reached that milestone point 600 feet below the space station. Commander Mike Bloomfield is taking over manual control for the remainder of today's rendezvous and docking of Atlantis to the international space station.

Piloting the shuttle from the aft control station on the flight deck of Atlantis, he will regularly pulse the shuttle's steering jets to keep the shuttle on the correct course.

The shuttle will make an arc from the point below to a point in front of the space station before beginning the final approach. Docking at the front of the station -- to the Destiny module -- is scheduled for 12:06 p.m. EDT.

1509 GMT (11:09 a.m. EDT)

Atlantis has now reached that milestone point 600 feet below the space station. Commander Mike Bloomfield is taking over manual control for the remainder of today's rendezvous and docking of Atlantis to the international space station.

Piloting the shuttle from the aft control station on the flight deck of Atlantis, he will regularly pulse the shuttle's steering jets to keep the shuttle on the correct course.

The shuttle will make an arc from the point below to a point in front of the space station before beginning the final approach. Docking at the front of the station -- to the Destiny module -- is scheduled for 12:06 p.m. EDT.

1509 GMT (11:09 a.m. EDT)

Distance now 1,150 feet. The massive U.S. solar arrays have been feathered. The Russian arrays will be moved by 500 feet. And so Mission Control has given the Atlantis crew a "go" to approach within 400 feet of the station.

1505 GMT (11:05 a.m. EDT)

Atlantis is about 1,700 feet from the space station.

1453 GMT (10:53 a.m. EDT)

Atlantis is now 1.2 miles from the station, closing at 9 feet per second.

In a pre-flight interview, commander Mike Bloomfield described the rendezvous to docking:

"The rendezvous is broken down into three distinct phases. The first phase is done strictly by the ground, and it basically happens when we lift off. Once we lift off, there's a group of folks on the ground that are already tracking the station, they're tracking the shuttle, and they're figuring out what burns, what maneuvers, we have to do during the first couple of days in order to get close to the International Space Station. So that's the first phase, everything is done from the ground.

"The second phase is done, basically, using the computers that are on board the shuttle and a thing we call the star tracker - it gathers data about where the station is relative to us, and we also have a radar on board that also gathers data about where the station is relative to the shuttle, and then we use the computers on board the shuttle to compute these burns or maneuvers to get us even closer to the International Space Station.

"Once we get within about two thousand feet of the International Space Station, then that's all done by looking out the window. So I'll be looking out the window, and we have a bunch of tools on board, if you will, that are used to help me make decisions about what burns I want to do by looking out the window in order to fly and do the final portion of the rendezvous. And it requires a whole team. Steve Frick will do a series of these burns, these on board burns that we talked about, so he's going to be running the checklist and making sure that all the burns are done correctly before I start flying it out the over...head window. Rex Walheim is going to be in the back with a handheld laser, and that's one of the ways that we can measure how far we are from the International Space Station, and that helps us determine what kind of burns we want to do. Ellen Ochoa and Jerry Ross are going to run the docking system, to make sure that that's set up the way it needs to be. And Jerry will also be in the back helping Rex make decisions about whether or not we do a fly-out.

"One of the last things we have to do, as we get close to the station, is we have to make sure that there is no angular misalignment between the shuttle and the International Space Station. And so there's a big target -- and you've probably seen this on all the other dockings -- that everybody looks at, the centerline camera with the cross, and we'll look at that target and it will tell us whether or not we have to make some attitude adjustments with the shuttle. And so, Jerry and Rex will be making that decision, and then we'll go in for the final docking."

1444 GMT (10:44 a.m. EDT)

The shuttle is now 2.5 miles from the station.

1434 GMT (10:34 a.m. EDT)

Atlantis' onboard radar shows the distance between the shuttle and station is now about 4.5 miles. Meanwhile, the station's solar arrays will soon be "feathered" so they are edge-on to the approaching shuttle. This is done to protect the arrays from the shuttle's thruster plumes.

1424 GMT (10:24 a.m. EDT)

Atlantis is currently 6.8 miles away from the International Space Station, closinng at about 12 miles per hour. That rate will be slowed as the shuttle gets closer to the station. Docking is scheduled for about 12:06 p.m. EDT. The two spacecraft will be over south-central China, to the southwest of Shanghai, at the time of docking.

We have posted a timeline of the crew's schedule for today and a detailed docking timeline.

WEDNESDAY, APRIL 10, 2002

Space shuttle Atlantis is on course to catch the International Space Station on Wednesday. The two craft are scheduled to dock at 12:05 p.m. EDT (1605 GMT), kicking off a week-long visit by Atlantis to deliver the central section of the station's backbone truss structure. Read docking preview story.

TUESDAY, APRIL 9, 2002

The seven Atlantis astronauts spent their first full day in space setting up and checking out the systems they will need for Wednesday's planned docking with the space station and testing the shuttle's robotic arm in preparation for mounting the S0 truss to the outpost on Thursday.

Docking is scheduled for around 12:05 p.m. EDT.

International Space Station crew members Yuri Onufrienko, Carl Walz and Dan Bursch tidied up their orbital home today and completed routine maintenance on the eve of the arrival of their first visitors since they were launched to the station back in December. After docking and hatch opening tomorrow, the two crews will run through a dress rehearsal of procedures which will be used on Thursday to maneuver the large S0 (S-Zero) Truss structure from Atlantis' cargo bay for mating to a capture device at the top of the Destiny module.

Earlier today, Atlantis astronauts Ellen Ochoa and Jerry Ross, the first man to fly in space seven times, were interviewed by two Indianapolis television stations and The Associated Press. Ross' record-setting flight was the topic of the day.

"It's actually kind of hard to believe I've been with NASA as long as I have and been given the opportunity to fly on so many different flights," said Ross, who became an astronaut in 1980. "The time has gone by very fast and I've enjoyed every minute of it."

Ross was asked if he felt like a "space hog" given that he's making his seventh flight while more than 60 astronauts are still awaiting their first launch.

"Well, if you look at the ratio of time at NASA compared to the number of flights, I think it's about the same as most of the other people who have been flying in space and some of them are, in fact, even faster-paced than me," he said. "I feel like I've worked very hard and I feel like each of us earned our flights in space and if the other folks stick around as long and work as hard, hopefully they'll have the opportunity to fly at least as many times."

1500 GMT (11:00 a.m. EDT)

The astronauts of space shuttle Atlantis -- commander Mike Bloomfield, pilot Steve Frick, and mission specialists Ellen Ochoa, Steve Smith, Rex Walheim, Jerry Ross and Lee Morin -- awakened by mission control at 5:44 a.m. EDT this morning by the song "The Best Years of Our Lives" performed by the Baha Men.

The astronauts' first full day in space is being spent setting up and checking out the systems they will need for tomorrow's planned docking with the space station, including rendezvous tools and the shuttle's docking mechanism. Atlantis' robotic arm also will be tested in preparation for mounting the S0 truss to the station on Thursday. And the crew will examine spacesuits to be worn during the mission's spacewalks.

MONDAY, APRIL 8, 2002

Barely beating the clock, the space shuttle Atlantis rocketed away through a breezy afternoon sky today and set off on a four-spacewalk flight to attach a $790 million truss to the international space station that eventually will span the length of a football field. Read full launch story.

Read our earlier status center coverage.