CAPE CANAVERAL -- Astronauts aboard the NASA’s
shuttle Discovery undocked from the International Space Station (ISS) early
Monday, beginning their two-day journey back to planet Earth.
Before departing the space station,
the STS-120
crew left behind a new bus-sized room, spare parts and the newest member of
the orbital laboratory’s Expedition 16 team—U.S. astronaut Dan Tani—who replaced fellow spaceflyer
Clay Anderson after tearful
goodbyes on Sunday.
"I miss you already. Fly safe,
get home safe,” Tani said after Discovery cast off from the space
station at 5:32 a.m. EST (1032 GMT) while both spacecraft flew
218 miles (350 kilometers) above the South Pacific Ocean. "Thanks not only for the great ride up, but
also the last year and a half together. I owe you one."
The multinational crew of astronauts
also relocated a massive piece of the space station's backbone, deployed its older
solar arrays and carried out an emergency repair when one array wing snagged
and tore during its unfurling.
Commander Pamela Melroy
and her crew spent about 10 days docked with the orbital laboratory, which is
now more than 60 percent complete. During those days, she made history as one
of two
female spacecraft commanders aboard the floating laboratory with ISS
commander Peggy Whitson.
"It's just been an honor and a
privilege to share the command of this mission with you," Melroy told Whitson yesterday before sequestering her crew inside
Discovery. The 46-year-old California native also thanked the rest of her crew.
"We simply could not have
accomplished the mission without everybody's help," Melroy
said Sunday. "This is one that we will always remember."
Round your partner
Shortly after slipping away from the
ISS, Discovery pilot George Zamka guided the shuttle on
a victory lap of sorts around the space station, known as a fly-around. The
maneuver helps visually document the progress of the space station and look for
anything unusual, such as loose thermal shielding or other issues. It also
gives astronauts their first glimpse of their orbital handiwork to continue ISS
assembly.
“You’ve seen the station
grow before your very eyes and know that you were a part of it,” Melroy said before Discovery’s Oct. 23 launch. “It’s
also kind of a dramatic thing to realize that it’s just a snapshot.”
The maneuver began after Zamka slowly drifted Discovery away from the ISS
to a distance of 400 feet (122 meters), then propelled the spacecraft into a
360-degree loop around the $100 billion space station at a distance of 600 feet
(183 meters) while crewmembers inside took photographs.
A computer
glitch prevented Zamka from using a trajectory guide
to assist his fly-around work. The pilot instead relied on information taken by
hand-held instruments operated by his crewmates and other tools as he gently
nudged Discovery’s controls to fly the 100-ton shuttle around the ISS.
“We’re
all just cheering Zambo on,” Melroy said, referring to Zamka
by his nickname. “It’s pretty challenging to do this and he’s
doing a fabulous job.”
With the completion of their busy
construction mission and now successful undocking, the crew is shifting
attention to tomorrow's late inspection of Discovery's shielded underbelly—a now-standard practice since the loss of Columbia in 2003. An earlier inspection and images taken by ISS crewmembers before
Discovery arrived at the station yielded no signs of damage.
The operation uses the shuttle's
sensor-packed extension boom to scan the entire shield. Robotic arm operators
will focus special attention on spots recorded as having possible micrometeorite
or orbital debris impacts (MMOD).
Rick LaBrode,
lead shuttle flight director, said sensors detected about nine potential dings
to the shuttle's wing leading edges during the mission. At some point during
the mission, such debris dinged one of Discovery's 2.5-inch (6.3-centimeter) thick windows.
Engineers are analyzing images of the slight damage sent down by Anderson yesterday.
"These are well within the
family of what we've seen," LaBrode said of the
potential chinks in thermal shielding. "There isn't any concern."
Discovery will hold its orbital
position in space until after the follow-up heat shield inspection, and could
return to the ISS in the event that any serious damage is discovered.
Extended stay
NASA tacked on an extra day to the
STS-120 mission after Tani discovered worrisome
metallic grit in a starboard set of gears, called the solar alpha rotary
joint (SARJ), used to orient solar wings toward the Sun during a spacewalk.
"As soon as we have time to
focus on the SARJ, we will focus on it," said ISS flight director Heather Rarick on Sunday. She noted that tape samples collected by Tani in the spacewalk "will certainly help" to
diagnose the problem and come up with an efficient solution.
The three-person space station crew—Whitson,
Tani and cosmonaut Yuri Malenchenko—will
perform a series of intense spacewalks starting Friday, now that Discovery has
departed to ready the ISS for its next shuttle visit in early December.
They will use the station’s
robotic arm to move its shuttle docking port, known as the Pressurized Mating Adapter-2
(PMA-2), to Harmony, unhook and relocate the joined Harmony-PMA modules, then
finish configuring the new room for the arrival of shuttle Atlantis and its
STS-122 crew before their planned Dec. 8 arrival.
Home in sight
Discovery is scheduled to land here
at NASA’s Kennedy Space Center (KSC) on Wednesday at 1:02 p.m. EST (1802
GMT).
Unlike the previous shuttle
Endeavour mission in August, whose landing was threatened by Hurricane Dean,
Discovery’s planned Earth return faces no significant weather threats at
this time, NASA officials at the Johnson
Space Center said Sunday.
Weather reports call for a 30
percent chance of scattered showers here on Wednesday.
Should ugly weather rear its head,
however, Discovery could land at California’s
Edwards Air Force Base at 2:28 p.m. EST (1928 GMT) or 4:02 p.m. EST (2102 GMT)
Wednesday. The shuttle might also land at Northrup New Mexico’s White Sands Space Harbor
at 2:31 p.m. EST (1931 GMT) or 4:04 p.m. EST (2104 GMT).
The shuttle could also make another
attempt to land at KSC around 2:35 p.m. EST (1935 GMT), if necessary.
NASA is broadcasting Discovery's
STS-120 mission live on NASA TV. Click
here for mission updates and NASA TV from SPACE.com.
SPACE.com Staff Writer Tariq Malik contributed to this story from New York City.
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