KENNEDY SPACE CENTER, FLA. - The plane carrying the crew of mission STS-121 taxis onto the Shuttle Landing Facility at NASA's Kennedy Space Center. The crew was at the Center for a three-day series of Terminal Countdown Demonstration Test (TCDT) activities. The TCDT includes equipment familiarization, emergency egress training and a simulated launch countdown. Mission STS-121 is scheduled to launch July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After a three-day series of Terminal Countdown Demonstration Test (TCDT) activities, the crew of mission STS-121 are leaving NASA's Kennedy Space Center to return to Houston. Waving on her way to the plane at the Shuttle Landing Facility is Mission Specialist Stephanie Wilson. The TCDT includes equipment familiarization, emergency egress training and a simulated launch countdown. Mission STS-121 is scheduled to launch July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After a three-day series of Terminal Countdown Demonstration Test (TCDT) activities, the crew of mission STS-121 are leaving NASA's Kennedy Space Center to return to Houston. Boarding the plane at the Shuttle Landing Facility are Mission Specialists Piers Sellers and Stephanie Wilson. The TCDT includes equipment familiarization, emergency egress training and a simulated launch countdown. Mission STS-121 is scheduled to launch July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After a three-day series of Terminal Countdown Demonstration Test (TCDT) activities, the crew of mission STS-121 are leaving NASA's Kennedy Space Center to return to Houston. Waving on his way to the plane at the Shuttle Landing Facility is Thomas Reiter of Germany, who represents the European Space Agency. The TCDT includes equipment familiarization, emergency egress training and a simulated launch countdown. Mission STS-121 is scheduled to launch July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After a three-day series of Terminal Countdown Demonstration Test (TCDT) activities, the crew of mission STS-121 are leaving NASA's Kennedy Space Center to return to Houston. Walking toward the plane at the Shuttle Landing Facility are Mission Specialists Lisa Nowak and Piers Sellers. The TCDT includes equipment familiarization, emergency egress training and a simulated launch countdown. Mission STS-121 is scheduled to launch July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After a three-day series of Terminal Countdown Demonstration Test (TCDT) activities, the crew of mission STS-121 are leaving NASA's Kennedy Space Center to return to Houston. Walking to the plane at the Shuttle Landing Facility are Commander Steven Lindsey (left) and Mission Specialist Michael Fossum. The TCDT includes equipment familiarization, emergency egress training and a simulated launch countdown. Mission STS-121 is scheduled to launch July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - In the White Room on Launch Pad 39B, STS-121 Mission Specialist Stephanie Wilson waits for final adjustments to her launch suit before entering Space Shuttle Discovery. The crew is taking part in a full dress rehearsal for launch, including countdown and culminating in main engine cutoff. The rehearsal is the final part of Terminal Countdown Demonstration Test (TCDT) activities that the crew has been involved in for two days. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Amanda Diller

KENNEDY SPACE CENTER, FLA. - STS-121 crew members follow the route to the slidewire baskets on Launch Pad 39B. They are taking part in emergency egress practice, part of the Terminal Countdown Demonstration Test (TCDT) activities that include a simulated countdown culminating in main engine cutoff. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 crew members wait to climb into the slidewire basket on Launch Pad 39B. They are taking part in emergency egress practice, part of the Terminal Countdown Demonstration Test (TCDT) activities that include a simulated countdown culminating in main engine cutoff. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 crew members follow the route to the slidewire baskets on Launch Pad 39B. They are taking part in emergency egress practice, part of the Terminal Countdown Demonstration Test (TCDT) activities that include a simulated countdown culminating in main engine cutoff. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 Mission Specialists Piers Sellers and Stephanie Wilson finish emergency egress practice on Launch Pad 39B. They and other crew members have been taking part in Terminal Countdown Demonstration Test (TCDT) activities that include a simulated countdown culminating in main engine cutoff. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 crew members wait for the release of the slidewire basket on Launch Pad 39B. They are taking part in emergency egress practice, part of the Terminal Countdown Demonstration Test (TCDT) activities that include a simulated countdown culminating in main engine cutoff. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 crew members follow the route to the slidewire baskets on Launch Pad 39B. They are taking part in emergency egress practice, part of the Terminal Countdown Demonstration Test (TCDT) activities that include a simulated countdown culminating in main engine cutoff. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 crew members wait to climb into the slidewire basket on Launch Pad 39B. They are taking part in emergency egress practice, part of the Terminal Countdown Demonstration Test (TCDT) activities that include a simulated countdown culminating in main engine cutoff. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - In the White Room on Launch Pad 39B, STS-121 Pilot Mark Kelly gets help from the closeout crew with final adjustments to his launch suit before entering Space Shuttle Discovery. The crew is taking part in a full dress rehearsal for launch, including countdown and culminating in main engine cutoff. The rehearsal is the final part of Terminal Countdown Demonstration Test (TCDT) activities that the crew has been involved in for two days. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Amanda Diller

KENNEDY SPACE CENTER, FLA. - In the White Room on Launch Pad 39B, STS-121 Mission Specialist Lisa Nowak has her launch suit checked by a member of the closeout crew before she enters Space Shuttle Discovery. The crew is taking part in a full dress rehearsal for launch, including countdown and culminating in main engine cutoff. The rehearsal is the final part of Terminal Countdown Demonstration Test (TCDT) activities that the crew has been involved in for two days. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Amanda Diller

KENNEDY SPACE CENTER, FLA. - In the White Room on Launch Pad 39B, STS-121 Mission Specialist Thomas Reiter gets help from the closeout crew with final adjustments to his launch suit before entering Space Shuttle Discovery. The crew is taking part in a full dress rehearsal for launch, including countdown and culminating in main engine cutoff. The rehearsal is the final part of Terminal Countdown Demonstration Test (TCDT) activities that the crew has been involved in for two days. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Amanda Diller

KENNEDY SPACE CENTER, FLA. - In the White Room on Launch Pad 39B, STS-121 Mission Specialists Michael Fossum (center) and Piers Sellers have their launch suits checked by the closeout crew before entering Space Shuttle Discovery. They are connected to portable cooling units keeping them cool while waiting to enter Space Shuttle Discovery. The crew is taking part in a full dress rehearsal for launch, including countdown and culminating in main engine cutoff. The rehearsal is the final part of Terminal Countdown Demonstration Test (TCDT) activities that the crew has been involved in for two days. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Amanda Diller

KENNEDY SPACE CENTER, FLA. - In the White Room on Launch Pad 39B, STS-121 Commander Steven Lindsey makes adjustments to his launch suit before entering Space Shuttle Discovery. Behind him is Mission Specialist Thomas Reiter. The crew is taking part in a full dress rehearsal for launch, including countdown and culminating in main engine cutoff. The rehearsal is the final part of Terminal Countdown Demonstration Test (TCDT) activities that the crew has been involved in for two days. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Amanda Diller

KENNEDY SPACE CENTER, FLA. - In the White Room on Launch Pad 39B, STS-121 Mission Specialist Michael Fossum enjoys a portable cooling unit keeping him cool while waiting to enter Space Shuttle Discovery. The crew is taking part in a full dress rehearsal for launch, including countdown and culminating in main engine cutoff. The rehearsal is the final part of Terminal Countdown Demonstration Test (TCDT) activities that the crew has been involved in for two days. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Amanda Diller

KENNEDY SPACE CENTER, FLA. - In the White Room on Launch Pad 39B, STS-121 Mission Specialist Stephanie Wilson and Pilot Mark Kelly pause for a photo opportunity before making final adjustments to their launch suits before entering Space Shuttle Discovery. The crew is taking part in a full dress rehearsal for launch, including countdown and culminating in main engine cutoff. The rehearsal is the final part of Terminal Countdown Demonstration Test (TCDT) activities that the crew has been involved in for two days. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Amanda Diller

KENNEDY SPACE CENTER, FLA. - The STS-121 crew concludes emergency egress practice from Launch Pad 39B with a photo at the top of the fixed service structure. From left are Mission Specialists Michael Fossum and Thomas Reiter, Pilot Mark Kelly, Commander Steven Lindsey, and Mission Specialists Lisa Nowak, Stephanie Wilson and Piers Sellers. Reiter is from Germany and represents the European Space Agency. The crew has been taking part in Terminal Countdown Demonstration Test (TCDT) activities that include a simulated countdown culminating in main engine cutoff. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - During Terminal Countdown Demonstration Test (TCDT) activities, the STS-121 crew gets instructions about emergency egress from the pad from Capt. George Hoggard (left), who is astronaut rescue team leader. Crew members are (from left) Mission Specialist Piers Sellers, Pilot Mark Kelly, Mission Specialists Stephanie Wilson and Lisa Nowak, Commander Steven Lindsey, and Mission Specialists Thomas Reiter and Michael Fossum. Part of the training will be driving an M-113, which is an armored personnel carrier. Mission STS-121 is designated for launch on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 Commander Steven Lindsey (left) and Pilot Mark Kelly take part in emergency egress practice, part of the Terminal Countdown Demonstration Test (TCDT) activities that include a simulated countdown culminating in main engine cutoff. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - The STS-121 crew listens to instructions on emergency egress from the pad. The crew members are (from left) Pilot Mark Kelly, Mission Specialists Piers Sellers, Lisa Nowak, Stephanie Wilson and Thomas Reiter, Commander Steven Lindsey, and Mission Specialist Michael Fossum. Reiter is from Germany and represents the European Space Agency. The crew is at Kennedy for Terminal Countdown Demonstration Test activities, including emergency egress training from the pad. They will also suit up in their orange flight suits for a simulated countdown to launch. Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - The STS-121 crew pose outside of Space Shuttle Discovery's hatch during prelaunch training at Launch Pad 39B. Kneeling in front is Mission Specialist Thomas Reiter of Germany, who represents the European Space Agency. Standing behind are (from left) Mission Specialists Thomas Fossum and Lisa Nowak, Commander Steven Lindsey (center), Pilot Mark Kelly, and Mission Specialists Piers Sellers and Stephanie Wilson. The crew is at Kennedy for Terminal Countdown Demonstration Test activities, including emergency egress training from the pad. They will also suit up in their orange flight suits for a simulated countdown to launch. Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 Mission Specialist Lisa Nowak takes part in emergency egress practice on Launch Pad 39B. She is taking part in Terminal Countdown Demonstration Test (TCDT) activities that include a simulated countdown culminating in main engine cutoff. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Seen in the foreground is STS-121 Michael Fossum, who is looking at the integrated cargo carrier, part of the payload for the mission, temporarily stored in the payload changeout room on Launch Pad 39B. He is dressed in a clean room suit, appropriate for the environmentally clean or "white room" condition in which the payload resides before being transferred to the shuttle's payload bay. In front of and below him is the multi-purpose logistics module Leonardo, which is carrying supplies and equipment for the International Space Station. The payload also includes the lightweight multi-purpose experiment support structure carrier. Crew members are at NASA's Kennedy Space Center for Terminal Countdown Demonstration Test activities, which include equipment familiarization and a simulated launch countdown. Mission STS-121 is scheduled for launch on Space Shuttle Discovery on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Inside the payload changeout room on Launch Pad 39B, STS-121 Mission Specialists Michael Fossum (left) and Piers Sellers check out part of the payload for the mission. They are dressed in clean room suits, appropriate for the environmentally clean or "white room" condition in which the payload resides before being transferred to the shuttle's payload bay. The payload includes the multi-purpose logistics module Leonardo, with supplies and equipment for the International Space Station; the lightweight multi-purpose experiment support structure carrier; and the integrated cargo carrier. Crew members are at NASA's Kennedy Space Center for Terminal Countdown Demonstration Test activities, which include equipment familiarization and a simulated launch countdown. Mission STS-121 is scheduled for launch on Space Shuttle Discovery on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Inside the payload changeout room on Launch Pad 39B, STS-121 Mission Specialists Michael Fossum and Lisa Nowak (facing the camera) get a look at part of the payload for the mission. They are dressed in clean room suits, appropriate for the environmentally clean or "white room" condition in which the payload resides before being transferred to the shuttle's payload bay. The payload includes the multi-purpose logistics module Leonardo, with supplies and equipment for the International Space Station; the lightweight multi-purpose experiment support structure carrier; and the integrated cargo carrier. Crew members are at NASA's Kennedy Space Center for Terminal Countdown Demonstration Test activities, which include equipment familiarization and a simulated launch countdown. Mission STS-121 is scheduled for launch on Space Shuttle Discovery on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Inside the payload changeout room on Launch Pad 39B, STS-121 Mission Specialist Lisa Nowak takes a close look at part of the payload for the mission. She is dressed in a clean room suit, appropriate for the environmentally clean or "white room" condition in which the payload resides before being transferred to the shuttle's payload bay. The payload includes the multi-purpose logistics module Leonardo, which is carrying supplies and equipment for the International Space Station, the lightweight multi-purpose experiment support structure carrier and the integrated cargo carrier. Crew members are at NASA's Kennedy Space Center for Terminal Countdown Demonstration Test activities, which include equipment familiarization and a simulated launch countdown. Mission STS-121 is scheduled for launch on Space Shuttle Discovery on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Inside the payload changeout room on Launch Pad 39B, STS-121 Mission Specialist Piers Sellers takes a close look at part of the payload for the mission. He is dressed in a clean room suit, appropriate for the environmentally clean or "white room" condition in which the payload resides before being transferred to the shuttle's payload bay. The payload includes the multi-purpose logistics module Leonardo, which is carrying supplies and equipment for the International Space Station, the lightweight multi-purpose experiment support structure carrier and the integrated cargo carrier. Crew members are at NASA's Kennedy Space Center for Terminal Countdown Demonstration Test activities, which include equipment familiarization and a simulated launch countdown. Mission STS-121 is scheduled for launch on Space Shuttle Discovery on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Inside the payload changeout room on Launch Pad 39B, STS-121 Mission Specialist Piers Sellers looks closely at payload elements installed on the integrated cargo carrier. He is dressed in a clean room suit, appropriate for the environmentally clean or "white room" condition in which the payload resides before being transferred to the shuttle's payload bay. At lower right is the multi-purpose logistics module Leonardo, which is carrying supplies and equipment for the International Space Station. The payload also includes the lightweight multi-purpose experiment support structure carrier. Crew members are at NASA's Kennedy Space Center for Terminal Countdown Demonstration Test activities, which include equipment familiarization and a simulated launch countdown. Mission STS-121 is scheduled for launch on Space Shuttle Discovery on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Inside the payload changeout room on Launch Pad 39B, STS-121 Mission Specialist Michael Fossum looks closely at part of the payload for the mission. He is dressed in a clean room suit, appropriate for the environmentally clean or "white room" condition in which the payload resides before being transferred to the shuttle's payload bay. At lower left is the multi-purpose logistics module Leonardo, which is carrying supplies and equipment for the International Space Station. The payload also includes the lightweight multi-purpose experiment support structure carrier and the integrated cargo carrier. Crew members are at NASA's Kennedy Space Center for Terminal Countdown Demonstration Test activities, which include equipment familiarization and a simulated launch countdown. Mission STS-121 is scheduled for launch on Space Shuttle Discovery on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Inside the payload changeout room on Launch Pad 39B, STS-121 Mission Specialist Lisa Nowak examines part of the payload for the mission. She is dressed in a clean room suit, appropriate for the environmentally clean or "white room" condition in which the payload resides before being transferred to the shuttle's payload bay. The payload includes the multi-purpose logistics module Leonardo, with supplies and equipment for the International Space Station; the lightweight multi-purpose experiment support structure carrier; and the integrated cargo carrier. Crew members are at NASA's Kennedy Space Center for Terminal Countdown Demonstration Test activities, which include equipment familiarization and a simulated launch countdown. Mission STS-121 is scheduled for launch on Space Shuttle Discovery on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 Pilot Mark Kelly takes his turn in an M-113, which is an armored personnel carrier. Behind him can be seen Mission Specialists Lisa Nowak and Thomas Reiter from Germany, who represents the European Space Agency. The STS-121 crew is taking turns driving the M-113 as part of Terminal Countdown Demonstration Test activities, which include emergency egress training from the pad and a simulated countdown. Mission STS-121 is designated for launch on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Following training in the M-113 armored personnel carrier, the STS-121 crew pose for a photo with Capt. George Hoggard, who is astronaut rescue team leader. From left are Pilot Mark Kelly, Mission Specialist Lisa Nowak, Hoggard, Commander Steven Lindsey, and Mission Specialists Michael Fossum, Stephanie Wilson, Thomas Reiter and Piers Sellers. Reiter is from Germany and represents the European Space Agency. The STS-121 crew is taking turns driving the M-113 as part of Terminal Countdown Demonstration Test activities, which include emergency egress training from the pad and a simulated countdown. Mission STS-121 is designated for launch on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 Commander Steven Lindsey takes his turn driving an M-113, which is an armored personnel carrier. The STS-121 crew is taking turns driving the M-113 as part of Terminal Countdown Demonstration Test activities, which include emergency egress training from the pad and a simulated countdown. Mission STS-121 is designated for launch on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 Mission Specialist Lisa Nowak takes her turn in an M-113, which is an armored personnel carrier. Behind her, at right, is Mission Specialist Thomas Reiter from Germany, and represents the European Space Agency. The STS-121 crew is taking turns driving the M-113 as part of Terminal Countdown Demonstration Test activities, which include emergency egress training from the pad and a simulated countdown. Mission STS-121 is designated for launch on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 Mission Specialist Thomas Reiter is taking his turn driving an M-113, which is an armored personnel carrier. Reiter is from Germany and represents the European Space Agency. The STS-121 crew is taking turns driving the M-113 as part of Terminal Countdown Demonstration Test activities, which include emergency egress training from the pad and a simulated countdown. Mission STS-121 is designated for launch on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 Mission Specialist Michael Fossum takes his turn in an M-113, which is an armored personnel carrier. The STS-121 crew is taking turns driving the M-113 as part of Terminal Countdown Demonstration Test activities, which include emergency egress training from the pad and a simulated countdown. Mission STS-121 is designated for launch on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 Mission Specialist Piers Sellers takes his turn in an M-113, which is an armored personnel carrier. Behind him are Mission Specialists Lisa Nowak and Thomas Reiter from Germany, who represents the European Space Agency. The STS-121 crew is taking turns driving the M-113 as part of Terminal Countdown Demonstration Test activities, which include emergency egress training from the pad and a simulated countdown. Mission STS-121 is designated for launch on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - STS-121 Mission Specialist Stephanie Wilson takes her turn in an M-113, which is an armored personnel carrier. Behind her, at right, is Mission Specialist Thomas Reiter from Germany, and represents the European Space Agency. The STS-121 crew is taking turns driving the M-113 as part of Terminal Countdown Demonstration Test activities, which include emergency egress training from the pad and a simulated countdown. Mission STS-121 is designated for launch on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Under the watchful eye of Capt. George Hoggard (left front), who is astronaut rescue team leader, STS-121 Commander Steven Lindsey takes his turn driving an M-113, which is an armored personnel carrier. Behind Lindsey and Hoggard are Mission Specialists Piers Sellers (waving) and Michael Fossum. The STS-121 crew is taking turns driving the M-113 as part of Terminal Countdown Demonstration Test activities, which include emergency egress training from the pad and a simulated countdown. Mission STS-121 is designated for launch on July 1. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After landing at NASA's Kennedy Space Center aboard a Grumman G2 aircraft, the STS-121 crew gathers at a microphone for the media. Seen here at center is Mission Specialist Lisa Nowak; at left is Pilot Mark Kelly. Other crew members are Mission Commander Steven Lindsey, Pilot Mark Kelly, and Mission Specialists Michael Fossum, Stephanie Wilson, Piers Sellers and Thomas Reiter, who represents the European Space Agency. The crew is at the space center to take part in a Terminal Countdown Demonstration Test, or TCDT. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After landing at NASA's Kennedy Space Center aboard a Grumman G2 aircraft, the STS-121 crew gathers at a microphone for the media. Seen here at center is Mission Specialist Stephanie Wilson; at right is Piers Sellers. Other crew members are Mission Commander Steven Lindsey, Pilot Mark Kelly, and Mission Specialists Michael Fossum, Lisa Nowak and Thomas Reiter, who represents the European Space Agency. The crew is at the space center to take part in a Terminal Countdown Demonstration Test, or TCDT. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - During a break in the rain storms from Tropical Storm Alberto, the STS-121 crew arrives at NASA's Kennedy Space Center aboard a Grumman G2 aircraft to take part in a Terminal Countdown Demonstration Test, or TCDT. Greeting the crew is Shuttle Launch Director Mike Leinbach, here shaking hands with Mission Specialist Thomas Reiter, who represents the European Space Agency. Other crew members are Mission Commander Steven Lindsey, Pilot Mark Kelly, and Mission Specialists Piers Sellers, Michael Fossum, Lisa Nowak and Stephanie Wilson. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After landing at NASA's Kennedy Space Center aboard a Grumman G2 aircraft, the STS-121 crew gathers at a microphone for the media. Seen here is Mission Specialist Thomas Reiter from Germany, who represents the European Space Agency. Other crew members are Commander Steven Lindsey, Pilot Mark Kelly, and Mission Specialists Michael Fossum, Lisa Nowak, Stephanie Wilson and Piers Sellers. The crew is at the space center to take part in a Terminal Countdown Demonstration Test, or TCDT. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After landing at NASA's Kennedy Space Center aboard a Grumman G2 aircraft, the STS-121 crew gathers at a microphone for the media. Mission Commander Steven Lindsey is introducing the crew, from left: Mission Specialist Michael Fossum, Pilot Mark Kelly, Mission Specialist Lisa Nowak, Lindsey, Mission Specialists Stephanie Wilson, Piers Sellers and Thomas Reiter, who represents the European Space Agency. The crew is at the space center to take part in a Terminal Countdown Demonstration Test, or TCDT. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After landing at NASA's Kennedy Space Center aboard a Grumman G2 aircraft, the STS-121 crew gathers at a microphone for the media. Seen here at center is Pilot Mark Kelly. Other crew members are Mission Commander Steven Lindsey and Mission Specialists Michael Fossum, Lisa Nowak, Stephanie Wilson, Piers Sellers and Thomas Reiter, who represents the European Space Agency. The crew is at the space center to take part in a Terminal Countdown Demonstration Test, or TCDT. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After landing at NASA's Kennedy Space Center aboard a Grumman G2 aircraft, the STS-121 crew gathers at a microphone for the media. Seen here at center is Mission Specialist Piers Sellers; at left is Mission Specialist Stephanie Wilson. Other crew members are Mission Commander Steven Lindsey, Mission Specialist Michael Fossum, Pilot Mark Kelly, and Mission Specialists Lisa Nowak and Thomas Reiter, who represents the European Space Agency. The crew is at the space center to take part in a Terminal Countdown Demonstration Test, or TCDT. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After landing at NASA's Kennedy Space Center aboard a Grumman G2 aircraft, the STS-121 crew gathers at a microphone for the media. Seen here is Mission Specialist Michael Fossum. Other crew members are Commander Steven Lindsey, Pilot Mark Kelly, and Mission Specialists Lisa Nowak, Stephanie Wilson, Piers Sellers and Thomas Reiter, who represents the European Space Agency. The crew is at the space center to take part in a Terminal Countdown Demonstration Test, or TCDT. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After their arrival at NASA's Kennedy Space Center, the STS-121 crew poses for a photo. From left are Mission Specialist Michael Fossum, Pilot Mark Kelly, Mission Specialist Lisa Nowak, Commander Steven Lindsey and Mission Specialists Stephanie Wilson, Piers Sellers and Thomas Reiter from Germany, who represents the European Space Agency. The crew is at the space center to take part in a Terminal Countdown Demonstration Test, or TCDT. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After landing at NASA's Kennedy Space Center aboard a Grumman G2 aircraft, Mission Commander Steven Lindsey pauses at a microphone to introduce the crew. Joining him are Mission Specialist Michael Fossum, Pilot Mark Kelly, and Mission Specialists Lisa Nowak (partly visible at left), Stephanie Wilson, Piers Sellers and Thomas Reiter, who represents the European Space Agency. The crew is at the space center to take part in a Terminal Countdown Demonstration Test, or TCDT. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - After landing at NASA's Kennedy Space Center aboard a Grumman G2 aircraft, Mission Commander Steven Lindsey pauses at a microphone to introduce the crew. Joining him are Mission Specialist Michael Fossum, Pilot Mark Kelly, and Mission Specialists Lisa Nowak (partly visible at left), Stephanie Wilson, Piers Sellers and Thomas Reiter, who represents the European Space Agency. The crew is at the space center to take part in a Terminal Countdown Demonstration Test, or TCDT. Over several days, the crew will practice emergency egress from the pad and suit up in their orange flight suits for the simulated countdown to launch. Space Shuttle Discovery is designated to launch July 1 on mission STS-121. It will carry supplies to the International Space Station. Photo credit: NASA/Kim Shiflett