CAPE
CANAVERAL, Fla. - NASA's space
shuttle Atlantis and its six-astronaut
crew are cleared to launch toward the International Space
Station (ISS) Sunday as long as the weather holds, shuttle managers said
today.
Atlantis is
poised to rocket toward the ISS at 4:29:57 p.m. EDT (2029:57 GMT) Sunday from
its Pad 39B launch site here at NASA's Kennedy Space Center (KSC) to haul new solar
wings and a bus-sized pair set of trusses to the ISS and jump start
construction of the orbital laboratory.
"We feel
like we're going into the weekend here in pretty good shape," said LeRoy Cain,
NASA's shuttle integration manager, in a press briefing. "We are go to continue
here into the launch countdown."
About the
only issue plaguing NASA's shuttle launch team and the STS-115 crew is the
weather. Current
forecasts predict a 60 percent chance of favorable flight conditions on
launch day, though remnant clouds from afternoon thunderstorms are still a
concern. Atlantis' heat resistant tiles can be damaged in rain, and persistent
electrically-charged anvil clouds are a lightning hazard during shuttle
flights.
Lightning
struck Atlantis' launch pad at about 2:00 p.m. EDT (1800 GMT) today, though all
initial reports indicate that the orbiter itself is functioning perfectly and
that safety measures performed as designed, said NASA launch director Michael
Leinbach, adding that heavy rain and afternoon thunderstorms prevented pad
workers from loading all of the cryogenic propellant used to power Atlantis'
fuel cells aboard the orbiter today. That activity is expected to resume by
9:00 p.m. EDT (0100 Aug. 26 GMT), he added.
The shuttle
is protected from weather at the launch pad by the shell-like Rotating Service
Structure, which swings into place when an orbiter is present. Metal cables run
from the ground up to the top of a mast on the pad's structure, serving as a
lightning rod that prevents lightning from striking NASA orbiters, Leinbach
said.
Shuttle and
ISS mission managers are also watching Tropical Storm Ernesto - formerly
Tropical Depression 5 - which is building strength as it approaches the Gulf of Mexico. While the storm could reach hurricane strength next week, it is not
expected to impact Sunday's planned STS-115 launch, Lt. Kaleb Nordgren, of the
45th Weather Squadron at Cape Canaveral Air Force Station, told
reporters.
There is a
slight chance that Ernesto, should it develop into much stronger storm and
maintain its present course into the Gulf, could impact Atlantis' shuttle
Mission Control Center, particularly if it hit reaches the Houston area and
forces an evacuation - which could effectively end the spaceflight early - but
it is still too early to tell, Cain said.
"The storms
that we're looking at right now are just too, too far away," Cain said.
A milestone
mission
Commanded
by veteran
NASA astronaut Brent Jett, Atlantis' STS-115
mission marks a return to ISS construction for the first time in more than
three years.
The 2003 loss of Columbia and
NASA's subsequent return to
flight effort have delayed shuttle missions to finish the half-built
space station, which saw its last major construction work during 2002's
STS-113 spaceflight.
Jett and
his STS-115 crewmates arrived here at KSC Thursday and expect a busy 11-day
mission. They will stage three
spacewalks in four days to connect their cargo - the integrated Port
3/Port 4 truss segments - to the space station's port side, deploy two
expansive solar arrays and wire up their power and cooling lines. Other tasks
include two heat shield inspections, the first to check Atlantis' for launch
debris impacts on Flight Day 2 and the final scan to detect any signs of damage
from orbital debris or micrometeorites.
The upcoming
spaceflight marks the first ISS construction mission since NASA's Endeavour
orbiter delivered the Port 1 (P1) truss to the station during 2002's STS-113
flight. Atlantis' P3/P4 truss segments are destined to be attached to the end
of that P1 truss, and are just the first of a series of elements that must be
launched and attached in order to complete the ISS by the 2010 retirement date
of NASA's shuttle fleet.
"This flight
has to work for the next flight to occur," said NASA ISS program manager
Michael Sufferdini. "The next few have to kind of happen in the right order."
NASA's
STS-115 mission is also a milestone for the agency's ISS partners such as the
Canadian Space Agency (CSA), which built the robotic arm - Canadarm2
- used aboard the station for assembly and other tasks. STS-115 astronaut Steven
MacLean will be the first from his country to actually use the Canadian-built
arm.
"In short,
we're proud, we're ready to go," said Benoît Marcotte, station program director
for the CSA, adding that his space agency - like NASA's other ISS partners - is
eager to resume station construction. "We're pleased to be where we are right
now and we're pleased to see the [assembly] sequence starting again."
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