The International Space Station with its newly spread solar wings approaches the horizon. Photo: NASA TV/Spaceflight Now
 
With hugs and handshakes, the Endeavour astronauts bid farewell to the crew of space station Alpha today, closed hatches between the two spacecraft and undocked to wind up an edge-of-the-seat mission to install a huge set of solar arrays.

Sailing 240 miles above the China-Kazakhstan border, Endeavour undocked and slowly dropped straight away from the international outpost at 2:13 p.m., six days 23 hours 13 minutes after linking up with the outpost Dec. 2.

Shuttle pilot Michael Bloomfield then guided Endeavour through a slow tail-first full-circle loop around the station for a detailed photo survey before firing the shuttle's maneuvering jets to leave the complex and it's three-man crew behind.

Videotape downlinked later showed the station serenely sailing above the cloud tops, it's huge new solar arrays extending 115 feet to either side of the complex like great black-and-gold wings, dwarfing the four smaller Russian arrays attached to the Zvezda and Zarya modules.

The station seen from below near the end of Endeavour's flyaround. Photo: NASA TV/Spaceflight Now

As Endeavour continued its looping fly around and dropped behind the station, Alpha seemed to float up over the limb of the Earth, silhouetted against the black night of space like a scene from a science fiction movie.

Normally stoic NASA officials stared at the scene in wonder. "Now that looks like a space station," one marveled.

"We are one gigantic step closer to putting on board the space station the beginnings of what can be the most sophisticated laboratory ever in space," said deputy chief flight director Milt Heflin. "We're right on the brink of doing that thanks to this mission."

Veteran shuttle commander Robert Cabana, now manager of international operations for the space station program, said "the space station has definitely spread its wings and is flying high on the success of this mission."

"It's just going to continue to grow by leaps and bounds, so hang on," he said. "I think Christmas came early to the international space station. I couldn't be more excited and happy for the entire team."

After testing re-entry systems Sunday, Endeavour's crew plans to glide back to a landing at the Kennedy Space Center at 6:04 p.m. Monday to close out the 101st flight in shuttle history.

"I'd be remiss if I didn't brag about the orbiter Endeavour a little bit, too," Heflin said. "We haven't talked about it, and that's probably good news because it has basically provided the platform for us to go do this work. Again, again and again.

"And this machine is built by men and women in this country, it's just a tribute to what this country can do when it puts its mind to something and builds hardware like that. The American people should be extremely proud of that piece of hardware."

The Endeavour crew say goodbye to station commander Shepherd. Photo: NASA TV/Spaceflight Now

Endeavour's five-man crew bid farewell to the three Alpha astronauts just before 11 a.m., gathering in the station's roomy Unity module for a traditional Navy departure ceremony.

Shuttle skipper Brent Jett, a Navy commander who graduated first in his class at the U.S. Naval Academy, first reported to Houston that his crew had accomplished all of the mission's objectives.

"And Houston, the STS-97 and Alpha crews are reporting that all solar array assembly activities are complete and all joint activities are complete and the STS-97 crew is departing Alpha," Jett said.

"And Houston copies. Thank you," replied astronaut Shannon Lucid in mission control.

Station skipper William Shepherd, a former Navy SEAL commando and graduate of the Naval Academy, stood by the ship's bell mounted on one of Unity's bulkheads to formally ring the departing crew off.

"And Houston, space station Alpha would like to thank Endeavour, its crew and the international team on the ground for bringing a great new capability on board station Alpha. Job well done," Shepherd radioed.

"And Captain Shepherd, the STS-97 crew requests permission to depart Alpha," Brent said.

"Permission granted. Endeavour departing," Shepherd called, ringing the ship's bell three times as the shuttle crew floated one by one back into the orbiter.

The flyaround carried Endeavour in front of the station, directly above it and then back to its starting point. It originally was designed to permit a large-format IMAX camera in the shuttle's cargo bay to photograph the station and the P6 solar power tower against the backdrop of planet Earth.

But the IMAX camera malfunctioned earlier in the mission and the crew had to settle for shooting the scene with the usual array of more traditional still, video and movie cameras.

The result was a stunning video that erases any doubt about the sheer size of the growing outpost.

Station commander Bill Shepherd and Endeavour crew members take in the view through a porthole in the Zvezda living quarters on Friday. Photo: NASA TV/Spaceflight Now

"We're not working any issues right now," Cabana said. "The space station's in good health. The arrays are performing flawlessly, we're delivering three to three-and-a-half kilowatts of power to the Russian segment and P6 is providing all the power to the (Unity) node. We've got plenty of electricity up there for a change."

With Endeavour's departure, Shepherd, Yuri Gidzenko and Sergei Krikalev will turn their attention to completing checkout of the P6 solar array and making preparations for arrival of the U.S. laboratory module, Destiny, in late January.

"I think the biggest things we have left are basically clean up from adding P6 (power system) aboard, which is the solar power array, making sure the gyros are happy, that they'll keep us lined up and we can control them when the lab is here," Shepherd said Friday.

But first the crew will take a few days off to relax after a heavy pre-docking workload.

Station flight director Jeff Hanley said Shepherd and company will get back to a more normal routine next week, unpacking equipment and supplies ferried up aboard Endeavour and reviewing procedures for manually redocking a Progress supply craft on Christmas day.

The supply ship was undocked Dec. 1 and moved into a parking orbit to make way for Endeavour. Russian flight controllers want to redock the Progress M1-4 vehicle to provide additional trash stowage volume and to test a software patch designed to correct guidance problems that derailed an automatic docking attempt Nov. 18.

As with the first docking, Gidzenko will remotely pilot the M1-4 spacecraft to a linkup with the station using the manual TORU system.

The P6 solar power tower is the largest structure ever erected in space. It's two solar wings stretch 240 feet from tip to tip, generating more than 50 kilowatts of power and making the station one of the brightest objects in the sky.

Endeavour's crew installed the 17.5-ton array Dec. 3 during the first of three spacewalks. The astronauts successfully wired the array into the station's electrical system and managed to tighten up a loose solar cell blanket during a final spacewalk Thursday.

The station and shuttle crews pictured through the hatch of Zvezda. Photo: NASA TV/Spaceflight Now

Hatches between the two spacecraft were finally opened Friday to permit equipment and supply transfers.

NASA managers hailed the mission as a complete success, saying the station now has more than enough power to support continued assembly, launch of the Destiny module in January and the start of scientific research next summer.

"We've accomplished all of our objectives," lead flight director William Reeves said Friday. "The crews are working together extremely well, the vehicle is performing very well, we're not working any anomalies. We should be in great shape for ... packing up and coming home Monday."

Said station flight director John Curry: "It's almost mind-boggling to me that this mission went this smoothly."

"Going into it, we knew there were going to be complications," he said. "We had two crews separated by hatches, we had three different control centers and all that has gone spectacularly. All of our mission objectives have been met."

Along with installing the P6 solar array, the astronauts made preparations for the lab assembly mission in January, installed a device to measure the station's electrical environment and carried out a complex series of thruster firings to precisely measure the station's structural rigidity.

Endeavour looks down on the space station as it soars high above the clouds. Photo: NASA TV/Spaceflight Now

As it turned out, the station responded to the structural dynamics test almost exactly as engineering models had predicted. And the Floating Potential Probe, designed to measure how much electrical charge might be building up on the new solar arrays, showed spacewalkers can remove lightning bolts from their list of concerns.

"We have already started collecting data and we can see that the plasma contactor units are clamping the voltage between the plasma and the station as was hoped and predicted," Reeves said. "It's working perfectly, we're seeing very low numbers."

As the station plows through the charged-particle environment of the extreme upper atmosphere, the new P6 solar wings can build up an electrical charge. Devices called plasma contactors spew a steady stream of xenon atoms into space to neutralize any such buildup.

But the plasma contactors provide no actual measurements of the plasma environment around the station. As a result, the Endeavour astronauts mounted the Floating Potential Probe atop the P6 truss to provide hard data. And, as Reeves said, the data show spacewalkers have nothing to fear.