Departure Day: Shuttle Discovery Undocks From Space Station

A very different International Space Station is seen with one Port 6 solar array folded away (center right) and a new portside segment (far right) in view taken from the space shuttle Discovery after undocking during NASA's STS-116 mission. CREDIT: NASA TV.

HOUSTON -- With heartfelt hugs and wide smiles, seven astronauts aboard NASA's shuttle Discovery departed the International Space Station (ISS) Tuesday after eight days of orbital construction work.

Discovery's STS-116 astronauts cast off from their ISS berth at 5:10 p.m. EST (2210 GMT), leaving a very different space station behind than the one they arrived at last week [image, video].

"For Alpha, from the crew of Discovery, we wish you smooth sailing," STS-116 commander Mark Polansky radioed to the ISS crew after undocking as both spacecraft flew over the eastern Pacific Ocean. "We hope you enjoy the new electrical system onboard station."

Polansky and his STS-116 crewmates installed a new portside piece of the ISS, overhauled the orbital laboratory's power grid and stayed an extra day for an unplanned fourth spacewalk to wrangle a wily solar array into its storage boxes on Monday.

The construction work leaves the station ready to accept new solar array segments, as well as European and Japanese laboratories currently set to launch aboard shuttle flights in the next two years. Discovery shuttle pilot William Oefelein flew the orbiter on a partial fly-around of the ISS after undocking, giving the STS-116 astronauts a bird's eye view of their orbital handiwork [image].

"It's always a goal to try and leave someplace in a better shape than it was when you came, and I think we've accomplished that," Polansky said before leaving the ISS. "I hope that we're really on our way to a great start for [ISS] assembly completion."

The seven STS-116 astronauts and three Expedition 14 spaceflyers recorded video and snapped photographs while exchanging handshakes, hugs and warm words to mark their separation [image].

Discovery is due to land at NASA's Kennedy Space Center on Friday at 3:56 p.m. EST (1856 GMT). Discovery must land no later than Saturday because of supply limitations.

"We bid a bittersweet farewell to Discovery," Expedition 14 commander Michael Lopez-Alegria said during a brief ceremony. "And we'd like to welcome Suni to our crew."

ISS crew change complete

One STS-116 astronaut, first-time spaceflyer Sunita "Suni" Williams, is remaining behind onboard the ISS as a member of its Expedition 14 crew. She is relieving European Space Agency (ESA) astronaut Thomas Reiter, who has lived and worked aboard the station in his arrival in July.

"I hope Discovery takes you home as smoothly and safely as it brought me here," Williams told Reiter.

Reiter is returning to Earth aboard Discovery, and received a warm send-off by Lopez-Alegria and fellow Expedition 14 flight engineer Mikhail Tyurin.

"By the power vested in me, which I just invented, we would like to make you an honorary member of NASA's astronaut corps," Lopez-Alegria said, dubbing the German spaceflyer a "model astronaut" and presenting him with makeshift NASA wings.

A veteran of two long-duration spaceflights, one to Russia's Mir and the other aboard ISS, Reiter's current mission returned the station to three-astronaut operations for the first time since the 2003 Columbia accident.

"It's been an exciting time, so it's hard to let go," Reiter said before leaving the space station. "I'm really excited to get back on the ground."

In addition to their ISS construction and crew exchange duties, Discovery's STS-116 astronauts delivered about 5,215 pounds (2,365 kilograms) of spare parts, new equipment and fresh supplies for the space station's crew. The orbiter left the outpost with about 3,725 pounds (1,689 kilograms) of unneeded supplies, completed experiments and other hardware.

Shuttle inspections on tap

Before landing, Discovery's astronaut crew has a few more tasks ahead, including a second heat shield survey and the launch of several microsatellites from a palette at the rear of the orbiter's payload bay.

Known as a late inspection, the heat shield survey is a mirror image of one performed on Dec. 10 and includes scans of the orbiter's vital heat-resistant panels along its wing leading edges and nose cap. Unlike the initial look, which was aimed at identifying any damage caused by shuttle external tank or ice during launch, late inspections target new impacts or dings from micrometeorite hits or orbital debris.

Discovery will take up a position about 40 miles (64 kilometers) from the ISS until the late inspection is complete, staying within range of the orbital laboratory - which can also serve as a shuttle safe haven - until the orbiter's heat shield is once more cleared for landing, NASA officials said.

Discovery carries three small technology-demonstrating satellites to be deployed in the next two days. Two are due for deployment after the heat shield inspection Wednesday, with the third to fly on Thursday.

Mission managers hope to land Discovery and its STS-116 astronauts at the Kennedy Space Center's Shuttle Landing Facility in Cape Canaveral, Florida, weather permitting. They are also preparing alternate runways at California's Edwards Air Force Base and New Mexico's White Sands Space Harbor if required.

• VIDEO: STS-116 Mission Profile: Undocking
• Images: The Spacewalks of NASA's STS-116
• Images: Discovery's STS-116 Launch Day Gallery
• STS-116 Video: Power is Everything
• STS-116 Video: Building Blocks
• Mission Discovery: The ISS Rewiring Job of NASA's STS-116
• Complete Space Shuttle Mission Coverage
• The Great Space Quiz: Space Shuttle Countdown
• All About the Space Shuttle