Astronauts Scott Parazynski and Dan Tani disconnected electrical grounding straps, used power tools to unscrew four bolts and then released a final capture latch holding the 35,000-pound P6 solar array truss segment in place atop the international space station.

Stephanie Wilson and Doug Wheelock, operating the space station's Canadian-built robot arm from inside the station's Destiny laboratory module, then carefully pulled the massive solar array segment away, the first step in a complex, two-day procedure to move P6 to the far left end of the station's main power truss.

The first bolt was unscrewed at 6:40 a.m. and about 15 minutes later, the capture claw was released.

"Just a quick observation, P6 is separated from Z1 by about an inch, already," Parazynski radioed at 6:57 a.m.

"Copy," Italian astronaut Paolo Nespoli radioed from inside the space shuttle. "It cannot wait to go."

"Yeah, it's just excited to get off the ISS," Parazynski joked.

After verifying no straps or wires remained connected to P6, Nespoli called Wilson and Wheelock: "Alpha, Discovery, for robotics. Doug, you have a go to take the baby away."

"Copy, go to demate P6," Wheelock replied. "And we also copied that (Parazynski and Tani) are in position to monitor separation."

"Verified, Wheels," Parazynski confirmed.

"Verified," Tani said.

Moments later, the arm began pulling P6 up and away from the Z1 truss extending up from the central Unity module.

"Good motion!" Parazynski said when the truss began pulling away. The spacewalkers monitored the slow separation procedure for a few minutes before moving back down the Z1 truss to stow tools in the station's airlock before pressing ahead with the rest of the day's work.

The P6 truss segment will remain "parked" on the end of the station arm overnight. It will be handed off to the shuttle's robot arm Monday and then, after the station arm is moved to an outboard work site, P6 will be handed back for installation and redeployment on the far left end of the power truss during a third spacewalk Tuesday.

With P6 successfully "demated," Parazynski is pressing ahead with work to continue outfitting the newly installed Harmony module, attached to the space station Friday. Tani, meanwhile, moved to equipment carts attached to a mobile transporter that creeps along the front of the solar array truss to move the station arm to various work sites. Engineers have noticed a discoloration on handrails on the carts and Tani took pictures to help engineers determine if there are any sharp edges or any other defects that could pose problems.

Tani also plans to inspect a massive rotary joint on the right side of the power truss to look for signs of anything that might be interfering with the joint's motion.

Higher-than-normal vibration and power usage have been noticed in recent weeks, prompting concern an insulation blanket or some other debris is causing friction in the mechanism. The station is equipped with two solar alpha rotary joints that slowly turn outboard solar arrays to keep them face on to the sun. Tani is not expected to attempt any repairs today, he is simply going to visually inspect the joint and take photographs to document the joint's current condition.

Tani and Parazynski also plan to attach a grapple fixture to Harmony later in the spacewalk that will be used by the station arm later, after Discovery departs, to move the module from its current, temporary attachment point to its permanent location on the front of the space station.

"Wow, beautiful terminator," Tani marveled earlier, watching sunrise approach high above the south Pacific Ocean. "The blue, red color around the Earth's terminator. Fantastic."

"You lucky dog, you get to see that for another..."

"...couple of months, yeah," Tani said.

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