The shuttle Atlantis, its hail-battered fuel tank finally repaired, is poised for blastoff June 8 to restart space station assembly after a five-month hiatus. The long-delayed flight is part of a critical sequence of missions to prepare the outpost for delivery of European and Japanese research modules late this year and early next.

The primary goal of Atlantis' mission is to attach a huge new set of solar panels to the right side of the station's main power truss, along with a powerful rotary joint to keep the huge arrays face on to the sun. The combined truss segments measure 44 feet nine inches long, 16 feet across and weigh 35,678 pounds. The two new solar panels, when fully extended, will stretch 240 feet from tip to tip and slowly rotate like giant paddle wheels.

The astronauts also hope to complete the retraction of another set of identical arrays, used to provide power to the lab complex during the initial stages of assembly, so it can be moved to its permanent position on the left end of the power truss later this year.

The crew of shuttle Discovery ran into major problems retracting one side of the P6 array in December and ultimately staged an unplanned spacewalk, manually shaking free stuck grommets on frayed guide wires to fold the pleated blind-like array into its storage canister. While Atlantis' crew hopes to benefit from lessons learned and retract the remaining blanket automatically, they will be standing by to provide hands-on spacewalk assistance if necessary.

"We're going to go through a process to try to slowly retract this array during the sequence of a couple of (spacewalks) so we'll have the crew available to help us as it is retracted and see if we can't sneak it in without shaking the array quite so much," said Mike Suffredini, space station program manager at the Johnson Space Center in Houston.

Attaching the new $367.3 million S3/S4 solar array truss segments, completing the retraction of P6 and ultimately re-extending its two wings on the port side of the main power truss later this year will clear the way for attachment of European and Japanese research modules, both major milestones on the road to completing the station in 2010.

"The S3/S4 will be the first set of solar arrays on the starboard side of the station," said Atlantis spacewalker James Reilly. "We currently have the port side arrays up, in the P3/P4 elements that were taken up (last year). What we're doing is bringing up the starboard set of arrays, and that's the foundation for the power supply that will now allow us to truly become an integrated International space station with the European and the Japanese labs."

In August, the shuttle Endeavour will carry supplies to the station and attach a spacer segment to the S4 solar array installed during Atlantis' mission to permit the eventual attachment of a fourth and final set of arrays, known as S6. Educator/astronaut Barbara Morgan, Christa McAuliffe's backup in the original Teacher in Space program, will operate the shuttle's robot arm to pull the S5 spacer segment out of the shuttle's cargo bay.

In October, Discovery will deliver a new multi-hatch node called Harmony, temporarily mounting it on the port side of the Unity module that connects the U.S. and Russian segments of the station. The astronauts then will move the retracted P6 solar array to its permanent location the left end of the main power truss in one of the most challenging assembly tasks yet attempted. If all goes well, the arrays will be re-extended, boosting the station's electrical power to between 70 and 90 kilowatts under ideal conditions.

After Discovery departs, the station crew will use the lab's robot arm to remove the shuttle docking port now on the forward end of the Destiny laboratory module and attach it to Harmony. The station astronauts then will move Harmony and its shuttle docking port to the front end of Destiny and stage a series of spacewalks to route power and cooling to the new module.

That will set the stage for the long-awaited December launch of the European Space Agency's Columbus research module, which will be attached to Harmony's starboard port. The Japanese Experiment Module will be bolted to Harmony's port hatch early next year.

"Everything now is pretty serial ... it is quite a production," said Clayton Anderson, a station crew member hitching a ride to the outpost aboard Atlantis. "We're going to put those pieces in place one step at a time and then if we do have any problems, we'll deal with those one step at a time such that we can get the Columbus module, the JEM modules on board the station, docked to Harmony, because that is a huge step to the international capability of the station. This is going to be a big four or five flights in a row."

Starting the year with a months-long delay was a major disappointment, especially with the shuttle's forced retirement looming in 2010 and with it, a hard deadline for completing the space station. But shuttle Program Manager Wayne Hale said the agency remains committed to putting safety ahead of schedule.

"We've got to be vigilant to make sure we don't allow ourselves to be driven by the schedule," he said. "We're flying these flights in the order that we can, as rapidly as it's reasonably possible to do it, but we fully intend to keep all of our safety practices in place. ... We cannot let schedule drive us to do something dumb.

"But at the same time, we really would like to get all these flights done by the time that the president and congress have told us to retire this set of vehicles. So, we're struggling a little bit to maintain the proper tension. And that's going to be with us until the end of the program."

Atlantis and its seven-member crew are scheduled for liftoff from pad 39A at the Kennedy Space Center on June 8 at 7:38 p.m., kicking off the first of four flights planned for 2007.

Launch of mission STS-117 is timed to coincide with the moment Earth's rotation carries the pad into the plane of the space station's orbit, setting up a two-day orbital chase and a docking around 3:38 p.m. on June 10. Three spacewalks, and possibly four, are planned to hook up and activate the new S3/S4 solar array segment and to complete the P6-2B retraction.

Atlantis' launch period extends through July 19. But a Lockheed Martin Atlas 5 rocket carrying a classified National Reconnaissance Office payload is scheduled for launch from the Cape Canaveral Air Force Station the morning of June 14. NASA can make four attempts to launch Atlantis over a five-day period - June 8, 9, 11 and 12 - before standing down for the Atlas and to top off on-board supplies of hydrogen and oxygen. The shuttle launch period would reopen on June 17, regardless of whether the Atlas went on June 14 or 15.

While Discovery's flight last December - STS-116 - to activate the station's main electrical system remains the most complex shuttle mission ever attempted, "when it comes to other big-picture assembly flights where you're talking robotics and EVA tasks and some commanding from the ground and activating new hardware, then this one's right up there," said Paul Hill, deputy director of the Mission Operations Directorate at the Johnson Space Center.

"We've got a full-volume payload," he said, "this thing is huge, not quite the size of a Greyhound bus, but it's big, and we're going to move this thing out as far as we can to install it and then send a couple of astronauts out there to finish getting it open and connected in and fire this thing up.

"If you think about the paths where this could go wrong, there's still a large number of them. We could still have arm problems pulling this thing out of the bay or trying to get it installed on station. We could have problems with the attachment system where we're trying to get this thing attached to the station well enough where it can handle loads without breaking off. We could have problems getting umbilicals connected to apply keep-alive power and we could have infant mortality."

"So you've got what's already a full flight of tough nuts and bolts assembly activities and right there in the critical path now is this trouble that we had retracting the (P6) solar array," Hill said. "So right up front for the flight control team and the crew is making sure they understand everything they can about everything they saw on that solar array on 116 so if they have to respond on 117 they can still get everything completed they plan to do and get that solar array fully in the can and end up undocking with four solar arrays out, two alpha joints tracking the sun and a P6 that's well on its way to being disconnected and moved outboard of P4.

"That's really what this is all about, keeping your fingers crossed and hoping there are no other surprises with this other solar array. We'll go out there and apply the things we learned coming out of 116 to get that solar array in, and come out of 117 looking really good and ready to install Harmony and ready to move P6."

At the controls aboard Atlantis will be commander Frederick Sturckow, a Marine Corps colonel, pilot Lee Archambault, an Air Force colonel, and flight engineer Steven Swanson. Their crewmates are Patrick Forrester, James Reilly, John "Danny" Olivas and Anderson. Sturckow and Reilly have two previous shuttle flights to their credit while Forrester has one. The rest are space rookies.

Reilly and Olivas will carry out the first and third spacewalks of the mission while Swanson and Forrester will conduct the second and, if necessary, the fourth.

NASA managers had hoped to launch Atlantis on mission STS-117, the first of five planned 2007 shuttle flights, March 15. Under the original schedule, Anderson was to launch in June aboard the Endeavour, replacing astronaut Sunita Williams aboard the station as a member of the Expedition 15 long-duration station crew.

But during a freak storm that thundered over the launch pad on Feb. 26, Atlantis' external tank was blasted by hail, suffering thousands of pits and gouges in its foam insulation. Wind gusts reached 62 knots and hail up to 1.5 inches in diameter was found at the pad.

Most of the damage was restricted to the upper liquid oxygen section of Atlantis' tank. Only a handful of dings were found lower down on the hydrogen section and while two dozen heat shield tiles on the orbiter were scraped by hail that worked its way behind weather protection panels, detailed inspections show the ship's critical carbon composite wing leading edge panels and nose cap were undamaged.

But the hail damage to the foam on the top of the tank was severe and Atlantis had to be hauled off the pad and moved back to the Vehicle Assembly Building for repairs. When all was said and done, the launch of Atlantis slipped to June while Endeavour and STS-118 moved to August.

Williams was launched to the space station aboard Discovery last December. NASA managers initially said she could safely remain aloft until August but after additional consideration, they decided to bring her home in June, as originally planned, but on mission STS-117 instead of STS-118. Staying up through August was not a health threat for Williams, officials said, but her cumulative exposure to space radiation could preclude a future station flight. And so, the decision was made to bring her back to Earth on schedule aboard Atlantis.

At the same time, NASA managers decided to move Anderson, Williams' replacement, from Endeavour to Atlantis.

"They're a crew of six that's trained to do everything by themselves so I kind of advertise myself as a utility infielder," Anderson said in an interview. "If commander Sturckow needs me to do something, then I'll do it. They're going to train me specifically for a few things and then since I do have station arm experience, on the ground anyway, I can help Lee Archambault when he installs the S3/S4 truss.

"Then as far as STS-118 goes, once those guys arrive I'll pretty much do the same jobs with them that I was planning on doing had I launched with that crew, and that includes EVAs three and four. And then I'll also be helping Charlie Hobaugh when he manipulates the arm to install the S5 truss."

Assuming an on-time launch and docking, Atlantis will undock June 17, leaving Anderson behind with Expedition 15 commander Fyodor Yurchikhin and flight engineer Oleg Kotov. Williams will return to Earth with Atlantis' crew, gliding to a touchdown at the Kennedy Space Center around 2:45 p.m. on June 19.

Anderson will remain aboard the station until late October, when the shuttle Discovery will deliver his replacement, astronaut Daniel Tani, during mission STS-120. Yurchikhin and Kotov will return to Earth about a week earlier aboard a Russian Soyuz spacecraft. Their replacements - Expedition 16 commander Peggy Whitson and Yuri Malenchenko - are scheduled to arrive aboard a Soyuz spacecraft Oct. 4, the 50th anniversary of the launch of Sputnik and the birth of the space age.

It will be up to the Expedition 16 crew - Whitson, Malenchenko and Tani - to oversee the attachment of the Harmony node and PMA-2 to the front of the Destiny lab module and the subsequent attachment of the Columbus research module during shuttle mission STS-122 in December.

Continue to Part 2 -->