CAPE
CANAVERAL, Fla. - Six NASA astronauts circling
the Earth aboard the space
shuttle Discovery are ready for their Monday landing after a busy mission
to the International Space Station (ISS).
NASA launch
and reentry flight director Steve Stitch, said Discovery's STS-121 astronauts,
commanded by shuttle flight veteran Steven
Lindsey, and their spacecraft are primed to trade orbital flight for a
runway here at NASA's Kennedy Space Center (KSC) tomorrow.
"My sense
was that they're getting a little bit excited," Stitch said during a mission
status briefing. "Tomorrow, they will have their game faces on and they'll be
ready to execute the deorbit prep and entry."
Lindsey and
his fellow STS-121
astronauts have two opportunities to land KSC's Shuttle Landing Facility
Monday, the first at 9:14 a.m. EDT (1314 GMT) and the second at 10:50 a.m. EDT
(1250 GMT). The shuttle can also land at KSC, as well as at alternate landing
sites in California or New Mexico, on Tuesday and Wednesday, Stitch said.
"If the
weather cooperates we'll try to try to get into Kennedy tomorrow," Stitch said.
Rain
showers are the only threat for Discovery's return Monday since they may come
within a 30-mile (48-kilometer) bubble surrounding NASA's landing facility,
Stitch said. Rain can damage the fragile - but vital - heat-resistant tiles
that protect Discovery from searing temperatures of reentry, he added.
Discovery's
crew is concluding a 13-day
mission to the International Space Station (ISS), where the astronauts delivered
a massive load of fresh cargo, one new
crewmember and made repairs
critical to the future construction of the orbital laboratory. NASA's STS-121
mission is agency's second shuttle test flight since the 2003 Columbia accident.
"We're
getting ready to come home," Lindsey told NBC News during a series of
space-to-ground interviews today.
Discovery's
crew spent much of their morning checking their spacecraft's systems to prepare
them for a Monday landing. They fired up an auxiliary power unit thought to
have a small
leak during a series of flight control system checks, but found no
issue for tomorrow's planned landing.
Lindsey and
Discovery pilot Mark
Kelly rehearsed their landing procedures with the aid of a handy computer
program and control stick, which the shuttle commander likened to a video game.
The STS-121 crew also stowed items into their final landing locations, NASA
said.
In addition
to Lindsey and Kelly, mission specialists Lisa
Nowak, Stephanie
Wilson, Piers
Sellers and Michael
Fossum are returning to Earth aboard Discovery.
Discovery's
new tires
Stitch said
that Discovery's Earth return will mark the first landing test a Global
Positioning Satellite (GPS) navigation system and hardier tires when it touches
down on KSC's Runway 33.
"For our
heavier missions, the tires that we were using are a little bit marginal for some
of our abort cases," Stitch said. "So we've added some additional load bearing
capabilities."
Made by
Michelin, Discovery's new tires can handle landings with up to a 20 percent
load increase and speeds 10 percent faster than normal parameters.
While
flight controllers have used a GPS navigation to track space shuttle in orbit,
Discovery's landing will be the first time the system is employed during a
landing, Stitch said.
The GPS
system is an addition to Discovery's orbital TACAN navigation system, and will
allow flight controllers to gain experience using it for future shuttle
missions.
"It's a
little bit of an improved accuracy than our TACAN system," Stitch said of the
new system.
NASA
officials said TACAN system aboard NASA's Endeavour orbiter has been replaced
by the GPS system for its STS-118 flight slated for summer 2007.
"We're
going to take it out for a spin on the STS-121 mission," Stitch added.
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