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