Astronaut Ellen Ochoa has successfully grappled the S0 Truss in shuttle Atlantis' cargo bay using the International Space Station's Canadarm 2 robotic arm. The 13 1/2 ton Truss was grappled at approximately 6:06 a.m. EDT.

Ochoa, assisted by ISS astronaut Dan Bursch, will now use the robotic arm to unberth and slowly move the Truss to a temporary capture device located at the top of the station's Destiny laboratory.

A series of four spacewalks will be required to permanently attach the 44-foot long Truss to the Destiny lab over the next week - the first scheduled to begin in about five hours from now, at 11:04 a.m. EDT.

Atlantis astronauts Steve Smith and Rex Walheim are now in the station's Quest Airlock making final preparations for their 6 1/2 hour-long spacewalk. They will deploy two of the four mounting struts as well as making the necessary electrical and data connections to power-up the S0 Truss.

The first milestone on one of the most complex and intricate days of space station assembly to date has been accomplished. Atlantis astronaut Ellen Ochoa, assisted by crewmate Lee Morin and ISS astronaut Dan Bursch, unberthed the S0 Truss from Atlantis' cargo bay using the International Space Station's Canadarm 2 robotic arm and successful moved it to a temporary parking location - a clamp on top of the station's Destiny laboratory. The entire operation took approximately 3 1/2 hours, starting at 6:06 a.m. EDT.

The 13 1/2 ton Truss will be permanently attached to the orbiting outpost by a pair of astronauts during a challenging spacewalk - scheduled to start in about ninety minutes at 11:04 a.m. EDT.

Atlantis astronauts Steve Smith and Rex Walheim are now in their spacesuits in the station's Quest Airlock, pre-breathing pure oxygen and making final preparations for their 6 1/2 hour-long spacewalk. The pair will deploy two of the four mounting struts that will secure the S0 segment to the station, as well as making the necessary electrical and data connections to power-up the 44-foot long truss.

Atlantis astronauts Steve Smith and Rex Walheim have exited from the International Space Station's Quest Airlock to start a planned 6 1/2 hour-long spacewalk. The spacewalk officially started at 10:36 a.m. EDT, about 30 minutes ahead of schedule.

The two astronauts will permanently attach the 13 1/2 ton S0 Truss, now temporarily "parked" on a clamp on top of the station's Destiny laboratory, deploying two of the four mounting struts that will secure the S0 segment to the station. They will also connect the electrical and data cables to power-up the 44-foot long truss, considered to be the "backbone" of the orbiting complex.

Spacewalk proceeding ahead of schedule
Thursday, April 11, 2002 at 12:45 p.m. EDT

Spacewalkers Steve Smith and Rex Walheim have attached the first of four struts to permanently connect the 44-foot long S0 Truss to the International Space Station's Destiny laboratory. The pair have completed about one-third of a planned 6 1/2 hour-long spacewalk that officially started at 10:36 a.m. EDT.

Smith and Walheim are now working to secure the second strut from the S0 Truss to Destiny - the remaining two struts will be secured during another spacewalk later in the mission. The two Atlantis astronauts will then connect the electrical and data cables to power-up the 44-foot long truss, considered to be the "backbone" of the orbiting complex.

All is proceeding well and the spacewalk is running slightly ahead of the timeline.

Spacewalkers struggle with sticky component
Thursday, April 11, 2002 at 3 p.m. EDT

Spacewalkers Steve Smith and Rex Walheim have attached the first two of four struts to permanently connect the 44-foot long S0 Truss to the International Space Station's Destiny laboratory - the remaining two struts will be secured during another spacewalk later in the mission. 

The pair have completed about two-thirds of a planned 6 1/2 hour-long spacewalk that officially started at 10:36 a.m. EDT.

Smith and Walheim are now connecting cables that supply electrical, data and cooling capability for the 44-foot long truss, considered to be the "backbone" of the orbiting complex. These cables are contained in a pair of "umbilical trays" - the aft umbilical tray was stuck and required extra effort from the two spacewalkers to unfold it into position.

The astronauts are literally "racing the clock" to make the necessary connections to supply vital cooling and power to maintain the proper temperature conditions for the S0 Truss.

Spacewalker Steve Smith is running low on oxygen and has been instructed to return to the International Space Station's Quest airlock to partially replenish his oxygen supply - this will allow him an additional 45 minutes of spacewalking time to assist partner Rex Walheim in completing connections on the S0 Truss.

Originally planned for 6 1/2 hours duration, today's spacewalk will now extend well beyond 7 hours. Atlantis astronauts Smith and Walheim ran into some difficulty unfolding an "umbilical tray" containing the connecting cables that supply electrical, data and cooling capability for the 44-foot long truss, considered to be the "backbone" of the orbiting complex.

Both spacewalkers had to grapple to un-stick the umbilical tray, originally scheduled as a one-man job, and that delay has put them behind schedule in making the vital connections that supply cooling and power to maintain the proper temperature conditions for the S0 Truss.

One minor task - the installation of circuit breaker devices - has been postponed to a spacewalk later in the mission.

Smith and Walheim successfully attached the first two of four struts to permanently connect the 44-foot long S0 Truss to the International Space Station's Destiny laboratory - the remaining two struts will be secured during another spacewalk later in the mission.

Astronauts Steve Smith and Rex Walheim have safely returned inside the International Space Station, following an exhausting 7 1/2 hour spacewalk - 1 1/4 hours longer than originally scheduled. The first of four spacewalks planned for this mission, today's excursion began at 10:36 a.m. EDT and concluded at 6:24 p.m. EDT.

At one point, Smith was running low on oxygen and was instructed to return to the station's Quest airlock to partially replenish his oxygen supply - this allowed him an additional 45 minutes of spacewalking time to assist partner Rex Walheim in completing connections on the S0 Truss.

Earlier, the two Atlantis astronauts successfully attached the first two of four struts to permanently connect the 44-foot long S0 Truss to the Destiny laboratory - the remaining two struts will be secured during another spacewalk later in the mission.

Smith and Walheim then ran into some difficulties unfolding an "umbilical tray" containing the connecting cables that supply electrical, data and cooling capability for the 44-foot long truss, considered to be the "backbone" of the orbiting complex.

Both spacewalkers had to grapple to un-stick the umbilical tray, originally scheduled as a one-man job, and that delay put them behind schedule in making the vital connections that supply cooling and power to maintain the proper temperature conditions for the S0 Truss. The S0 Truss is operating as expected and within its range of thermal conditions. 

One minor task - the installation of circuit breaker devices - has been postponed to a spacewalk later in the mission.

Following a grueling 7 1/2 hour spacewalk, Atlantis astronauts Steve Smith and Rex Walheim are likely sleeping soundly after working outside the International Space Station for the better part of a day. The first of four spacewalks planned for this mission, Thursday's excursion by Smith and Walheim began at 10:36 a.m. EDT and concluded at 6:24 p.m. EDT - about 90 minutes longer than planned.

The spacewalk followed a series of intricate maneuvers by Atlantis astronaut Ellen Ochoa, assisted by crewmate Lee Morin and ISS astronaut Dan Bursch, to unberth the S0 Truss from Atlantis' cargo bay using the station's Canadarm 2 robotic arm and successfully move it to a temporary parking location - a clamp on top of the station's Destiny laboratory.

Smith and Walheim then attached the first two of four struts to permanently connect the 44-foot long S0 Truss to the Destiny laboratory - the remaining two struts will be secured during another spacewalk later in the mission.

The spacewalking duo hurriedly connected cables that supply electrical, data and cooling capability for the 44-foot long truss, literally "racing the clock" to provide power and cooling connections required to maintain the proper temperature conditions. These cables were contained in a pair of umbilical trays - one of which jammed, requiring extra effort from the two astronauts to unfold it into position.

Smith and Walheim also attached an umbilical system from the truss to the "first railcar in space," the Mobile Transporter, enabling it to move up and down the length of the station to position the Canadarm 2 for future assembly work.

Flight controllers report that the S0 Truss has been activated and that all of the initial systems appear to be in excellent shape.

The Atlantis and ISS Expedition Four crews will combine forces today to transfer supplies, equipment and experiments between the shuttle and the newly-expanded International Space Station - a rather mundane task in contrast to yesterday's dramatic installation of the crucial S0 Truss and a marathon 7 1/2 hour spacewalk by astronauts Steve Smith and Rex Walheim.

Atlantis' seven astronauts were awakened at 4:44 a.m. EDT this morning to the sounds of "Testify to Love" by Wynonna Judd, requested by commander Mike Bloomfield's family.

Oxygen and nitrogen will be transferred from Atlantis into the station to replenish supplies in the Quest airlock for use during future spacewalks. The astronauts will also set up plant and crystal growth experiments in the station's Destiny laboratory.

Systems on the S0 Truss are functioning well since its installation. Today, ground controllers will activate systems on the Truss that will provide navigation and attitude data for the orbiting complex.

The combined crews of shuttle Atlantis and the International Space Station spent the day Friday transferring experiments, equipment and supplies into the station. Oxygen and nitrogen tanks in the Quest airlock were also replenished from supplies onboard Atlantis for use in future spacewalks.

Four new computers on the newly-installed S0 Truss were checked-out, as were Global Positioning System devices to determine the station’s orientation. The Thermal Control System is also performing as expected on the 13 1/2 ton Truss, considered to the station's "backbone" for future expansion, including additional trusses and solar array towers.

Atlantis astronauts Jerry Ross and Lee Morin also prepared for their Saturday spacewalk, scheduled to begin around 10:30 a.m. EDT. Ross and Morin will attach the second pair of struts to secure the S0 Truss to the orbiting complex. The pair will also attach a second umbilical system to the so-called "rail car," or Mobile Transporter, that will eventually enable the station’s Canadarm 2 robotic arm to move up and down the entire length of the completed truss.

Grandfathers prepare for spacewalk
Saturday, April 13, 2002 at 9 a.m. EDT

The first pair of spacewalking grandfathers in history are making final preparations for a hard day's work outside the International Space Station.

Atlantis astronauts Jerry Ross and Lee Morin are in the station's Quest airlock, pre-breathing oxygen and checking out their spacesuits, prior to their planned 6 1/2 hour spacewalk - scheduled to start at 10:34 a.m. EDT.

The Atlantis crew woke-up at 4:44 a.m. EDT to the sounds of "Voodoo Chile" by Jimi Hendrix, requested by spacewalker Lee Morin's wife. The ISS Expedition Four crew were also awakened at that time.

Astronaut Ellen Ochoa will repeat her crucial role as the operator of the station's Canadarm 2 robotic arm. Morin, wearing a spacesuit with diagonal broken stripes, will work from a platform at the end of 58-foot long Canadarm 2 during today's excursion. Wearing the spacesuit with broken red stripes will be Jerry Ross, adding to his record as NASA's most experienced spacewalker.

Ross and Morin will attach the second pair of struts to secure the S0 Truss to the orbiting complex. The pair will also attach a second umbilical system to the so-called "rail car," or Mobile Transporter, that will eventually enable the station’s Canadarm 2 robotic arm to move up and down the entire length of the completed truss.

Astronauts begin 6 1/2 hour spacewalk
Saturday, April 13, 2002 at 10:45 a.m. EDT

Astronauts Jerry Ross and Lee Morin, the first pair of spacewalking grandfathers in history, have exited the International Space Station's Quest airlock to start their planned 6 1/2 hour excursion. The spacewalk began at 10:09 a.m. EDT - about 25 minutes ahead of schedule.

Astronaut Ellen Ochoa is repeating her pivotal role as the operator of the station's Canadarm 2 robotic arm. Morin, wearing a spacesuit with diagonal broken stripes, will work from a platform at the end of the 58-foot long Canadarm 2 during today's session. Wearing the spacesuit with broken red stripes will be Jerry Ross, adding to his record as NASA's most experienced spacewalker - this is his eighth time working outside in space.

Ross and Morin will attach the second pair of struts to secure the S0 Truss to the orbiting complex. The pair will also attach a second umbilical system to the so-called "rail car," or Mobile Transporter, that will eventually enable the station’s Canadarm 2 robotic arm to move up and down the entire length of the completed truss.

Spacewalk proceeding as planned
Saturday, April 13, 2002 at 1:15 p.m EDT

Spacewalkers Jerry Ross and Lee Morin have completed about one-third of a planned 6 1/2 hour excursion outside the International Space Station. The second of four spacewalks planned for this mission, Ross and Morin stepped out of the station's Quest airlock at  10:09 a.m. EDT - about 25 minutes ahead of schedule - and the spacewalk is proceeding on schedule.

Ross and Morin have attached the third of four struts to permanently connect the 44-foot long S0 Truss to the station's Destiny laboratory and are now working to secure the final strut to the lab.

Atlantis astronaut Ellen Ochoa, assisted by ISS crew member Carl Walz, is operating the station's Canadarm 2 robotic arm. Morin, wearing a spacesuit with diagonal broken stripes, is working from a platform at the end of the 58-foot long Canadarm 2 during today's session.

Jerry Ross, NASA's most experienced spacewalker marking his eighth time working in space, is wearing the spacesuit with broken red stripes. The pair will soon attach a second umbilical system to the so-called "rail car," or Mobile Transporter, that will eventually enable the Canadarm 2 to move up and down the entire length of the completed truss.

Spacewalk enters final hour
Saturday, April 13, 2002 at 4:30 p.m EDT

Atlantis astronauts Jerry Ross and Lee Morin have about one hour to go before re-entering the International Space Station's Quest airlock to complete their spacewalk which will run about 7 1/4 hours - 45 minutes longer than originally planned. Today's spacewalk began at 10:09 a.m. EDT.

Ross and Morin successfully attached the third and four struts to permanently connect the 44-foot long S0 Truss to the station's Destiny laboratory. The pair also attached a second umbilical system to the so-called "rail car," or Mobile Transporter, that will eventually enable the Canadarm 2 to move up and down the entire length of the completed truss.

The two spacewalkers are now performing some "get ahead" work in preparation for tomorrow's excursion by Steve Smith and Rex Walheim.

Astronauts complete 7 1/2 hour spacewalk
Saturday, April 13, 2002 at 5:50 p.m EDT

Atlantis astronauts Jerry Ross and Lee Morin have re-entered the International Space Station's Quest airlock after completing a 7 1/2 hour spacewalk - about one hour longer than originally planned. Today's spacewalk began at 10:09 a.m. EDT and concluded at 5:39 p.m. EDT.

This was the first spacewalk conducted by a pair of grandfathers and it maintained Jerry Ross' status as NASA's all-time spacewalking leader, marking the eighth time Ross has worked outside of a spacecraft.

Atlantis astronaut Ellen Ochoa, assisted by ISS crew member Carl Walz, operated the station's Canadarm 2 robotic arm to maneuver Morin who worked from a platform at the end of the 58-foot long Canadarm 2.

Ross and Morin successfully attached the third and four struts to permanently connect the 44-foot long S0 Truss to the station's Destiny laboratory. The pair also attached a second umbilical system to the so-called "rail car," or Mobile Transporter, that will eventually enable the Canadarm 2 to move up and down the entire length of the completed truss.

The two spacewalkers also performed some "get ahead" work in preparation for tomorrow's excursion by Steve Smith and Rex Walheim.

Atlantis boosts space station orbit
Saturday, April 13, 2002 at 11:30 p.m EDT

The "Silver Team" - Atlantis astronauts Jerry Ross and Lee Morin - are now sleeping after completing a 7 1/2 hour spacewalk working on the International Space Station. Saturday's spacewalk began at 10:09 a.m. EDT and concluded at 5:39 p.m. EDT - about one hour longer than originally planned.

The 54-year old Ross and 49-year old Morin - the first team of spacewalking grandfathers - extended and bolted the final two struts of the new S0 Truss to the station's Destiny laboratory. The pair also attached a second umbilical system to the so-called "rail car," or Mobile Transporter, that will eventually enable the Canadarm 2 to move up and down the entire length of the completed truss.

The other team of Atlantis' spacewalkers, Steve Smith and Rex Walheim, will venture back outside Sunday to continue the outfitting of the truss and to reroute electrical power to the station’s 58-foot long robotic arm. The excursion is expected to start at around 10:30 a.m. EDT.

Also on Saturday, Pilot Steve Frick fired Atlantis’ engines in a one-hour procedure to slowly reboost the space station's altitude by about 2 miles.

Astronauts prepare for Sunday spacewalk
Sunday, April 14, 2002 at 8:15 a.m EDT

A pair of Atlantis astronauts are set to spend their Sunday walking in space. Steve Smith and Rex Walheim will conduct their second spacewalk of the mission to continue installation work on the 44-foot long S0 Truss, now secured to the station’s Destiny laboratory.

The two astronauts are scheduled to exit the Quest airlock at about 10:34 a.m. EDT to being their 6½-hour spacewalk.

Walheim, wearing a solid white spacesuit, will work from a platform at the end of the station's Canadarm 2 robotic arm. Atlantis crewmate Ellen Ochoa will manipulate the Canadarm 2, assisted by ISS flight engineer Dan Bursch.

Walheim and Smith, wearing the spacesuit with red stripes, will release a claw-like device on the top of the Destiny lab that was used to temporarly secure the Truss after it was unberthed from Atlantis' payload bay. The pair will install circuit breakers in the Truss and continue connecting cables that will route power, data and video for future Canadarm 2 operations

Later in the spacewalk, Smith and Walheim will shift their attention to the so-called "rail car," the Mobile Transporter, removing a radiator cover, releasing restraints used during launch, and making electrical connections. Their final task will be the installation of the Airlock Spur - a 14-foot long beam with handrails that will extend from the Quest airlock to the forward side of the S0 Truss.

The seven-member Atlantis crew woke up at 4:52 a.m. EDT to the sounds of “All Star,” performed by Smash Mouth from the Shrek movie soundtrack, requested by spacewalker Rex Walheim's family.

A pair of Atlantis astronauts have started their Sunday walk in space about 45 minutes ahead of schedule. Steve Smith and Rex Walheim have just exited from the International Space Station's Quest airlock to begin their second spacewalk of the mission. The excursion was officially under way at 9:48 a.m. EDT.

Walheim, wearing a solid white spacesuit, will work from a platform at the end of the shuttle's Canadarm robotic arm. Atlantis pilot Steve Frick will manipulate the Canadarm.

Walheim and Smith, wearing the spacesuit with red stripes, will release a claw-like device on the top of the Destiny lab that was used to temporarly secure the Truss after it was unberthed from Atlantis' payload bay. The pair will install circuit breakers in the Truss and continue connecting cables that will route power, data and video for future Canadarm 2 operations

Later in the spacewalk, Smith and Walheim will shift their attention to the so-called "rail car," the Mobile Transporter, removing a radiator cover, releasing restraints used during launch, and making electrical connections. Their final task will be the installation of the Airlock Spur - a 14-foot long beam with handrails that will extend from the Quest airlock to the forward side of the S0 Truss.

Spacewalkers Steve Smith and Rex Walheim have completed about one-third of a planned 6 1/2 hour excursion outside the International Space Station and all is proceeding well. This spacewalk, the second of the mission for Smith and Walheim, officially started at 9:48 a.m. EDT, about 45 minutes ahead of schedule

Walheim, wearing a solid white spacesuit, is working from a platform at the end of the shuttle's Canadarm robotic arm with Atlantis pilot Steve Frick manipulating the controls. Walheim will later move to a similar position on the station's Canadarm 2 to perform several tasks.

Walheim and Smith, who is wearing the spacesuit with red stripes, have released a claw-like device on the top of the Destiny lab that was used to temporarily secure the Truss after it was unberthed from Atlantis' payload bay. The pair are installing circuit breakers in the Truss and rerouting cables that will provide power, data and video for future Canadarm 2 operations

Smith and Walheim have shifted their attention to the so-called "rail car," the Mobile Transporter, removing a radiator cover, releasing restraints used during launch, and making electrical connections.

Their final task will be the installation of the Airlock Spur - a 14-foot long beam with handrails that will extend from the Quest airlock to the forward side of the S0 Truss.

Spacewalkers Steve Smith and Rex Walheim are in the final minutes of a planned 6 1/2 hour excursion outside the International Space Station and are wrapping up their activities. This spacewalk, the second of the mission for Smith and Walheim, officially started at 9:48 a.m. EDT, about 45 minutes earlier than planned.

All but one of the major tasks planned for this spacewalk - the third of four slated for this mission - have been accomplished.

Mission Control has just informed the astronauts that they want to end the spacewalk at the planned time today - both previous spacewalks have been extended. This means that today's spacewalk will finish in about one hour from now  - roughly 4:15 p.m. EDT.

Walheim, wearing a solid white spacesuit, has been working from a platform at the end of the shuttle's Canadarm robotic arm with Atlantis pilot Steve Frick manipulating the controls. Smith, who is wearing the spacesuit with red stripes, and Walheim released a claw-like device on the top of the Destiny lab that was used to temporarily secure the Truss after it was unberthed from Atlantis' payload bay.

The pair installed circuit breakers in the S0 Truss and rerouting cables that will provide power, data and video for future Canadarm 2 operations. Smith and Walheim also worked on the so-called "rail car," the Mobile Transporter, removing a radiator cover, releasing restraints used during launch, and making electrical connections.

The final task planned for today's spacewalk - the installation of the Airlock Spur, a 14-foot long beam with handrails that will extend from the Quest airlock to the forward side of the S0 Truss - has been deferred until Tuesday's fourth and final spacewalk.

Spacewalkers Steve Smith and Rex Walheim have safely completed their Sunday excursion outside the International Space Station and reentered the Quest airlock. This spacewalk, the second of the mission for Smith and Walheim, officially started at 9:48 a.m. EDT and concluded at 4:15 p.m. EDT - for a total duration of 6 hours, 27 minutes.

All but one of the major tasks planned for today's spacewalk - the third of four slated for this mission - were accomplished.

Smith and Walheim released a claw-like device on the top of the Destiny lab that was used to temporarily secure the Truss after it was unberthed from Atlantis' payload bay. The pair also installed circuit breakers in the S0 Truss and rerouting cables that will provide power, data and video for future Canadarm 2 operations.

The two astronauts also worked on the so-called "rail car," the Mobile Transporter, removing a radiator cover, releasing restraints used during launch and making electrical connections.

The final task planned for today - the installation of the Airlock Spur, a 14-foot long beam with handrails that will extend from the Quest airlock to the forward side of the S0 Truss - was deferred until Tuesday's fourth and final spacewalk.

Atlantis astronauts Steve Smith and Rex Walheim spent the day Sunday rewiring the International Space Station's Canadarm 2 robotic arm, as well as removing a radiator cover and releasing bolts on the station's "railcar" - the Mobile Transporter - during a 6 hour, 27 minute spacewalk.

Smith and Walheim's excursion - their second spacewalk and the third of this mission - accomplished all but one of the major tasks scheduled. The installation of the Airlock Spur, a 14-foot long beam with handrails that will extend from the Quest airlock to the forward side of the S0 Truss, was deferred until Tuesday's fourth and final spacewalk.

The spacewalkers released a claw-like device on the top of the Destiny lab that was used to temporarily secure the Truss after it was unberthed from Atlantis' payload bay. The pair also installed circuit breakers in the S0 Truss and rerouted cables that will provide power, data and video for future Canadarm 2 operations.

The focus now shifts to Monday morning's critical test run of the Mobile Transporter - the so-called "railcar". The 1,900 pound Mobile Transporter will be ordered to move about 32 feet up and down the Truss at a little less than one inch per second. This initial run will test the computers, drive motors, suspension unit, video and data cables and the first section of rails on the 44-foot long Truss.

Also, Atlantis pilot Steve Frick fired the Orbiter's steering jets tonight for about one hour to boost the space station's orbit by two miles.

Software troubles plague station railway test
Monday, April 15, 2002 at 10:15 a.m. EDT

Ground controllers believe that an anomaly in the software on the International Space Station "railway" has caused the 1,900 pound Mobile Transporter (MT) to halt and enter a "safing" mode. Preliminary indications from experts on the ground are that the automatic software needs to "learn" how to react to the behavior of the various sensing devices along the railcar's tracks as they operate in microgravity.

The Robotics Officer in Houston will send commands to manually unlatch the Mobile Transporter from its current location which, coincidentally, is where it needs to be parked to support the next space station utilization flight scheduled for launch next month. Later in the day, ISS astronaut Carl Walz will again attempt to command the railcar to move to another work location further down the Truss and back again.

The Mobile Transporter was being ordered to move about 26 feet up and down the Truss at a little less than one inch per second. This initial run was designed to test the computers, drive motors, suspension unit, video and data cables and the first section of rails on the 44-foot long Truss.

Another test planned for station "railway"
Monday, April 15, 2002 at 1:15 p.m. EDT

Experts at Mission Control are confident that the International Space Station's 1,900 pound Mobile Transporter, the so-called "railcar", is operating properly but that its automated software needs to "learn" how to react to the behavior of the various magnetic sensing devices along the railway tracks as they operate in microgravity. This morning's initial test was scrubbed after the railcar unexpectedly halted and went into a "safe" mode after reaching its first work location.

The Robotics Officer in Houston has been uplinking commands to manually unlatch the Mobile Transporter from its parked location which, coincidentally, is precisely where it needs to be located to support the next space station utilization flight scheduled for launch next month. Within the hour, ISS astronaut Carl Walz will again attempt to command the railcar to move to another work location further down the Truss and then back again.

The Atlantis crew will spend some time reviewing plans for tomorrow's fourth and final spacewalk. A press conference featuring all ten crewmembers of Atlantis and the ISS Expedition Four has just concluded.

Software hiccup halts railway test again
Monday, April 15, 2002 at 3:30 p.m. EDT

A second attempt to automatically move the International Space Station's 1,900 pound Mobile Transporter, the so-called "railcar", met with the same result as the first - an unannounced station stop. During both of today's tests, the railcar moved smoothly to its intended work location, then was abruptly halted by automatic software that placed the device into a "safe" mode.

Experts at Mission Control insist that both the Mobile Transporter and its software are operating properly but it appears that the software needs to be tweaked to "learn" how to react to the behavior of the various magnetic sensing devices along the railway tracks as they operate in microgravity. The effects of weightlessness, that cannot be accurately duplicated on Earth, actually cause the railcar to float above the tracks by a microscopic 50/1000 of an inch. The information received from magnetic micro-switches along the railway track is not being properly understood by the software which then shuts down the Mobile Transporter.

During this second test, the railcar was moved about 17 feet from its first halted position, known as Work Site 4, to a point farther down the track, Work Site 5. The Robotics Officer in Houston will now repeat a procedure that followed the first aborted test - uplink commands to manually latch and unlatch the Mobile Transporter from its parked location; then, move the railcar back to the Work Site 4 position and secure it there. Work Site 4 is where the railcar must be located to support the next space station utilization flight scheduled for launch next month.

Astronauts prepare for final spacewalk
Monday, April 15, 2002 at 9:30 p.m. EDT

Atlantis grandfathers Jerry Ross and Lee Morin will make the final spacewalk of the mission Tuesday, further extending Ross' tenure as NASA's most prolific spacewalker. The pair are scheduled to step outside the International Space Station's Quest airlock at about 10:30 a.m. EDT to begin a planned 6 ½ hour excursion outside the station.

Ross and Morin's primary task will be the installation of the Airlock Spur - a 14-foot long beam with handrails that will extend from the Quest airlock to the forward side of the S0 Truss to act as a "pathway" for future spacewalks. The pair will also install external lights on the Unity module, test micro-switches on the sides of the S0 Truss, troubleshoot a bolt on a cable-cutting system on the Mobile Transporter and secure a piece of insulation on one of four GPS antennas on the Truss.

Engineers are evaluating the mixed results from two tests Monday to automatically move the International Space Station's 1,900 pound Mobile Transporter, the so-called "railcar." On both occasions, the railcar moved smoothly to its intended work location, then was abruptly halted by automatic software that placed the device into a "safe" mode.

Experts at Mission Control insist that both the Mobile Transporter and its software are operating properly but it appears that the software needs to be tweaked to "learn" how to react to the behavior of the various magnetic sensing devices along the railway tracks as they operate in microgravity. The effects of weightlessness, that cannot be accurately duplicated on Earth, actually cause the railcar to float above the tracks by a microscopic 50/1000 of an inch. The floating interferes with magnetic sensors that tell the Mobile Transporter where it is located relative to each worksite as the sensors are losing contact with magnetic positioning strips on the Truss railway, preventing an automatic latching of the railcar.