KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. From left are mission specialists Joseph Tanner and Heidemarie Stefanyshyn-Piper. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. At right is commander Brett Jett. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. From left are mission specialists Heidemarie Stefanyshyn-Piper and Steven MacLean, who represents the Canadian Space Agency. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 pilot Christopher Ferguson looks over the mission payload one more time before launch. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. From left are mission specialists Heidemarie Stefanyshyn-Piper, Steven MacLean, representing the Canadian Space Agency, Daniel Burbank and Joseph Tanner. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. In front is mission specialist Heidemarie Stefanyshyn-Piper. Mission specialist Joseph Tanner is holding a camera, and behind him is mission specialist Steven MacLean, representing the Canadian Space Agency. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. Looking up at the payload from left, are mission specialists Steven MacLean, who represents the Canadian Space Agency, Heidemarie Stefanyshyn-Piper, Joseph Tanner, and Daniel Burbank. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. From left are mission specialists Heidemarie Stefanyshyn-Piper, Steven MacLean, representing the Canadian Space Agency, Daniel Burbank and Joseph Tanner. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. From left are mission specialist Steven MacLean, representing the Canadian Space Agency, and pilot Christopher Ferguson. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. From left are mission specialists Joseph Tanner and Heidemarie Stefanyshyn-Piper. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. From left are mission specialists Joseph Tanner, Daniel Burbank, Steven MacLean, who represents the Canadian Space Agency, and Heidemarie Stefanyshyn-Piper (standing). The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. From left are mission specialists Heidemarie Stefanyshyn-Piper and Steven MacLean, representing the Canadian Space Agency. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

KENNEDY SPACE CENTER, FLA. - In the payload changeout room on Launch Pad 39B, STS-115 crew members look over the mission payload one more time before launch. From front to back are mission specialists Joseph Tanner, Daniel Burbank, Steven MacLean, who represents the Canadian Space Agency, and Heidemarie Stefanyshyn-Piper. The mission crew has been at KSC to take part in Terminal Countdown Demonstration Test activities, which include emergency egress training, a simulated launch countdown and the payload familiarization. The TCDT is a prelaunch preparation for the mission that is scheduled to lift off in a window opening Aug. 27. During their 11-day mission to the International Space Station, the STS-115 crew will continue construction of the station and attach the payload elements, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Cory Huston

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