KENNEDY SPACE CENTER, Fla. -- STS-118 Mission Specialist Alvin Drew completes suitup for the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, Fla. -- STS-118 Mission Specialist Tracy Caldwell fixes her helmet during suitup for the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown here is Mission Specialist Steven MacLean, who is with the Canadian Space Agency. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown Shown here is Mission Specialist Daniel Burbank. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown here is Commander Brent Jett. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. -- STS-118 Pilot Charlie Hobaugh suits up for the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, Fla. -- STS-118 Mission Specialist Barbara R. Morgan finishes suitup for the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. Morgan joined NASA's Teacher in Space program in 1985 and was selected as an astronaut in 1998. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, Fla. -- STS-118 Mission Specialist Tracy Caldwell suits up for the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown here is Mission Specialist Heidemarie Stefanyshyn-Piper. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. -- STS-118 Mission Specialist Dave Williams, who represents the Canadian Space Agency, is eager to start the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

CAPE CANAVERAL, Fla. -- The crew of space shuttle Discovery's STS-124 mission arrive at NASA Kennedy Space Center's Shuttle Landing Facility to take part in the Terminal Countdown Demonstration Test, or TCDT. Mission Specialist Mike Fossum is greeted by Shuttle Launch Director Mike Leinbach. TCDT is a rehearsal for launch that includes practicing emergency procedures, handling on-orbit equipment, and simulating a launch countdown. On the STS-124 mission, the crew will deliver and install the Japanese Experiment Module – Pressurized Module and Japanese Remote Manipulator System. Discovery's launch is targeted for May 31. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown here being helped with his helmet is Pilot Christopher Ferguson. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. -- STS-118 Mission Specialist Alvin Drew is eager to begin the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown here is Mission Specialist Joseph Tanner. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. -- STS-118 Pilot Charlie Hobaugh's launch and entry suit is monitored after his suitup for the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, Fla. -- STS-118 Mission Specialist Rick Mastracchio gets help suiting up before the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, Fla. -- STS-118 Mission Specialist Dave Williams, who represents the Canadian Space Agency, completes suitup before the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown here being helped with his glove is Pilot Christopher Ferguson. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown here is Commander Brent Jett. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown here adjusting his glove is Mission Specialist Joseph Tanner. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. -- STS-118 Commander Scott Kelly's launch and entry suit is monitored after his suitup for the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown here is Mission Specialist Daniel Burbank. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. -- STS-118 Mission Specialist Rick Mastracchio adjusts his helmet during suitup before the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

CAPE CANAVERAL, Fla. -- The crew of space shuttle Discovery's STS-124 mission arrive at NASA Kennedy Space Center's Shuttle Landing Facility to take part in the Terminal Countdown Demonstration Test, or TCDT. Here, Commander Mark Kelly is greeted by Shuttle Launch Director Mike Leinbach. Behind Leinbach is Mission Specialist Greg Chamitoff. TCDT is a rehearsal for launch that includes practicing emergency procedures, handling on-orbit equipment, and simulating a launch countdown. On the STS-124 mission, the crew will deliver and install the Japanese Experiment Module – Pressurized Module and Japanese Remote Manipulator System. Discovery's launch is targeted for May 31. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, Fla. -- STS-118 Commander Scott Kelly gets help suiting up before the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. - After the conclusion of Terminal Countdown Demonstration Test (TCDT) activities at NASA’s Kennedy Space Center, STS-114 Commander Eileen Collins briefly talks to media about the importance of the TCDT as pre-launch training. The TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

S96-08027 (22 April 1996) --- The crew talk to the news media at Launch Pad 39B, at the Kennedy Space Center (KSC). From left are astronauts Andrew S. W. Thomas, mission specialist; Mario Runco, Jr., mission specialist; John H. Casper, commander; Daniel W. Bursch, mission specialist; Marc Garneau, mission specialist representing the Canadian Space Agency (CSA); and Curtis L. Brown, Jr., pilot. The astronauts are at KSC for the Terminal Countdown Demonstration Test (TCDT), a dress rehearsal for launch, the Space Shuttle Endeavour is undergoing preparations at Pad 39B for liftoff on the fourth Shuttle flight of 1996 around May 16, 1996.

S96-08025 (22 April 1996) --- The STS-77 crew arrives at the Kennedy Space Center's (KSC) Shuttle Landing Facility (SLF) for the Terminal Countdown Demonstration Test (TCDT), a dress rehearsal for launch. Shown here is Curtis L. Brown, Jr., pilot, who will be embarking on his third spaceflight when the Space Shuttle Endeavour lifts off on the STS-77 mission in mid-May. Over the next several days, the six-member crew will participate in emergency egress training at the pad and a simulated launch countdown that includes the entire launch team.

KENNEDY SPACE CENTER, FLA. - The STS-115 crew members are suiting up for their simulated launch countdown. Shown here fixing his glove is Mission Specialist Steven MacLean, who is with the Canadian Space Agency. The mission crew is at KSC for Terminal Countdown Demonstration Test (TCDT) activities that are preparation for launch on Space Shuttle Atlantis, scheduled to take place in a window that opens Aug. 27. The TCDT has included emergency egress training as well as the simulation. 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. -- STS-120 Mission Specialist Paolo Nespoli arrives in the white room on Launch Pad 39A. After donning a parachute pack, he will enter space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Pilot George Zamka finishes getting into his parachute pack before entering space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Commander Pamela Melroy is helped by the closeout crew in donning a parachute pack before she crawls through the open hatch into space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Mission Specialist Doug Wheelock is ready to enter space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Mission Specialist Doug Wheelock dons his parachute pack before entering space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

CAPE CANAVERAL, Fla. -- After their arrival at NASA Kennedy Space Center's Shuttle Landing Facility, the crew of space shuttle Discovery's STS-124 mission gather for a group photo. The crew is at Kennedy to take part in the Terminal Countdown Demonstration Test, or TCDT. From left are Mission Specialist Greg Chamitoff, Pilot Ken Ham, Mission Specialist Karen Nyberg, Commander Mark Kelly and Mission Specialists Ron Garan, Mike Fossum and Akihiko Hoshide, who represents the Japan Aerospace Exploration Agency, or JAXA. TCDT is a rehearsal for launch that includes practicing emergency procedures, handling on-orbit equipment, and simulating a launch countdown. On the STS-124 mission, the crew will deliver and install the Japanese Experiment Module – Pressurized Module and Japanese Remote Manipulator System. Discovery's launch is targeted for May 31. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, Fla. -- The STS-118 crew walks out of the Operations and Checkout Building, heading for Launch Pad 39A and a simulated launch countdown. On the left, Pilot Charlie Hobaugh leads one column, with Mission Specialist Rick Mastracchio behind him. On the right, Commander Scott Kelly leads, with Mission Specialists Tracy Caldwell and Dave Williams behind. Not pictured are Mission Specialists Alvin Drew and teacher-turned-astronaut Barbara R. Morgan. The countdown concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Mission Specialists Daniel Tani (left) and Doug Wheelock are ready to enter space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, Fla. -- The smiling STS-118 crew walks toward the Astrovan that will take them to Launch Pad 39A for a simulated launch countdown. From left are Mission Specialists Barbara R. Morgan and Rick Mastracchio, Pilot Charlie Hobaugh, Mission Specialists Dave Williams and Tracy Caldwell, and Commander Scott Kelly. Morgan joined NASA's Teacher in Space program in 1985 and was selected as an astronaut in 1998. The countdown concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, Fla. -- The STS-118 crew walks toward the Astrovan that will take them to Launch Pad 39A for a simulated launch countdown. From left are Mission Specialists Barbara R. Morgan and Rick Mastracchio, Pilot Charlie Hobaugh, Mission Specialists Dave Williams and Tracy Caldwell, and Commander Scott Kelly. Morgan joined NASA's Teacher in Space program in 1985 and was selected as an astronaut in 1998. The countdown concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Commander Pamela Melroy is helped by the closeout crew in donning a parachute pack before she crawls through the open hatch into space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. Her name patch reflects the nicknames the crew gave each other for the event. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, the closeout crew helps STS-120 Mission Specialist Stephanie Wilson with her parachute pack before entering space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Mission Specialist Daniel Tani (foreground) is helped with his launch suit preparations before entering space shuttle Discovery for a simulated launch countdown. In the background is Mission Specialist Doug Wheelock. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, the closeout crew helps STS-120 Pilot George Zamka to get into a parachute pack before entering space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. His name patch reflects the nicknames the crew gave each other for the event. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Mission Specialist Scott Parazynski dons his parachute pack before entering space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. His name patch reflects the nicknames the crew gave each other for the event. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, Fla. -- The STS-118 crew heads into the Astrovan that will take them to Launch Pad 39A for a simulated launch countdown. First in is Commander Scott Kelly. Following, right to left, are Pilot Charlie Hobaugh and Mission Specialists Tracy Caldwell, Dave Williams, Rick Mastracchio, teacher-turned-astronaut Barbara R. Morgan and Alvin Drew. The countdown concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- STS-120 Commander Pamela Melroy is donning her launch and entry suit to take part in a simulated launch countdown, part of the prelaunch terminal countdown demonstration test, or TCDT. Her name patch reflects the nicknames the crew gave each other for the event. The TCDT provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization, emergency training and the simulated countdown. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Launch of Discovery on mission STS-120 is targeted for Oct. 23 at 11:38 a.m. EDT on a 14-day mission. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. -- STS-120 Mission Specialist Stephanie Wilson is helped with her boot during suitup for a simulated launch countdown, part of the prelaunch terminal countdown demonstration test, or TCDT. Her name patch reflects the nicknames the crew gave each other for the event. The TCDT provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization, emergency training and the simulated countdown. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Launch of Discovery on mission STS-120 is targeted for Oct. 23 at 11:38 a.m. EDT on a 14-day mission. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. -- STS-120 Pilot George Zamka completes suiting up to take part in a simulated launch countdown, part of the prelaunch terminal countdown demonstration test, or TCDT. His name patch reflects the nicknames the crew gave each other for the event. The TCDT provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization, emergency training and the simulated countdown. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Launch of Discovery on mission STS-120 is targeted for Oct. 23 at 11:38 a.m. EDT on a 14-day mission. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Mission Specialist Scott Parazynski gets ready to enter space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Mission Specialist Stephanie Wilson adjusts her launch suit before entering space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, Fla. -- STS-118 Mission Specialist Barbara R. Morgan is helped with her helmet during suitup for the simulated launch countdown that concludes the terminal countdown demonstration test, or TCDT. Teacher-turn-astronaut Morgan is making her first space flight. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- STS-120 Mission Specialist Stephanie Wilson completes suiting up to take part in a simulated launch countdown, part of the prelaunch terminal countdown demonstration test, or TCDT. His name patch reflects the nicknames the crew gave each other for the event. The TCDT provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization, emergency training and the simulated countdown. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Launch of Discovery on mission STS-120 is targeted for Oct. 23 at 11:38 a.m. EDT on a 14-day mission. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- The crew of space shuttle Discovery's STS-124 mission arrive at NASA Kennedy Space Center's Shuttle Landing Facility to take part in the Terminal Countdown Demonstration Test, or TCDT. Here, Commander Mark Kelly (center left) and Mission Specialist Greg Chamitoff (center right) are greeted by Shuttle Launch Director Mike Leinbach (far left) and NASA Flow Director for Discovery Stephanie Stilson. TCDT is a rehearsal for launch that includes practicing emergency procedures, handling on-orbit equipment, and simulating a launch countdown. On the STS-124 mission, the crew will deliver and install the Japanese Experiment Module – Pressurized Module and Japanese Remote Manipulator System. Discovery's launch is targeted for May 31. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. -- STS-120 Commander Pamela Melroy completes suiting up to take part in a simulated launch countdown, part of the prelaunch terminal countdown demonstration test, or TCDT. His name patch reflects the nicknames the crew gave each other for the event. The TCDT provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization, emergency training and the simulated countdown. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Launch of Discovery on mission STS-120 is targeted for Oct. 23 at 11:38 a.m. EDT on a 14-day mission. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. -- STS-120 Mission Specialist Paolo Nespoli completes suiting up to take part in a simulated launch countdown, part of the prelaunch terminal countdown demonstration test, or TCDT. Nespoli represents the European Space Agency. His name patch reflects the nicknames the crew gave each other for the event. The TCDT provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization, emergency training and the simulated countdown. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Launch of Discovery on mission STS-120 is targeted for Oct. 23 at 11:38 a.m. EDT on a 14-day mission. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. -- STS-120 Pilot George Zamka is donning his launch and entry suit to take part in a simulated launch countdown, part of the prelaunch terminal countdown demonstration test, or TCDT. His name patch reflects the nicknames the crew gave each other for the event. The TCDT provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization, emergency training and the simulated countdown. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Launch of Discovery on mission STS-120 is targeted for Oct. 23 at 11:38 a.m. EDT on a 14-day mission. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Mission Specialist Paolo Nespoli dons a parachute pack before entering space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- STS-120 Mission Specialist Doug Wheelock completes suiting up to take part in a simulated launch countdown, part of the prelaunch terminal countdown demonstration test, or TCDT. His name patch reflects the nicknames the crew gave each other for the event. The TCDT provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization, emergency training and the simulated countdown. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Launch of Discovery on mission STS-120 is targeted for Oct. 23 at 11:38 a.m. EDT on a 14-day mission. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, Fla. -- Members of the STS-118 crew enjoy breakfast together before the next event in their Terminal Countdown Demonstration Test (TCDT), a dress rehearsal for launch. Following the meal, the crew will don their flight suits and board Space Shuttle Endeavour for a simulated countdown. From left are Mission Specialists Alvin Drew and the Canadian Space Agency's Dave Williams, Pilot Charlie Hobaugh, Commander Scott Kelly, and Mission Specialists Tracy Caldwell, Rick Mastracchio and teacher-turned-astronaut Barbara R. Morgan. TCDT activities also include M-113 armored personnel carrier training, payload familiarization, and emergency egress training at the pad. The STS-118 payload includes the S5 truss, a SPACEHAB module and external stowage platform 3. The mission is the 22nd flight to the International Space Station and is targeted for launch on Aug.7. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- STS-120 Mission Specialist Scott Parazynski arrives on Launch Pad 39A to start a simulated launch countdown, culmination of the prelaunch terminal countdown demonstration test, or TCDT. His name patch reflects the nicknames the crew gave each other for the event. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, FLA. -- In the white room on Launch Pad 39A, STS-120 Pilot George Zamka (left) and Mission Specialist Scott Parazynski are ready to enter space shuttle Discovery for a simulated launch countdown. The countdown is the culmination of the prelaunch terminal countdown demonstration test, or TCDT. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/George Shelton

KENNEDY SPACE CENTER, Fla. -- The STS-118 crew walks toward the Astrovan that will take them to Launch Pad 39A for a simulated launch countdown. On the left are Pilot Charlie Hobaugh leading the way and Mission Specialist Rick Mastracchio. ON the right, Commander Scott Kelly leads with (front to back) Mission Specialists Tracy Caldwell, Dave Williams and Alvin Drew. Not visible is teacher-turned-astronaut Barbara R. Morgan, also a mission specialist. The countdown concludes the terminal countdown demonstration test, or TCDT. The STS-118 crew has been at Kennedy for the TCDT activities that also include M-113 training, payload familiarization and emergency egress training at the pad. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/George Shelton

Crew members of space shuttle mission STS-120 prepare to board the bus that will transport them to Launch Pad 39A.

KENNEDY SPACE CENTER, FLA. - After the conclusion of Terminal Countdown Demonstration Test (TCDT) activities at NASA’s Kennedy Space Center, STS-114 Mission Specialist Soichi Noguchi speaks to the media about his experiences in his first TCDT. Noguchi is with the Japan Aerospace Exploration Agency. The TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

S96-08026 (22 April 1996) --- The STS-77 crew take time out from Terminal Countdown Demonstration Test (TCDT) activities to pose for a group portrait next to the slidewire baskets on the emergency egress system at the 195-feet level of Launch Pad 39B, at the Kennedy Space Center (KSC). From the left are astronauts Daniel W. Bursch, mission specialist; John H. Casper, commander; Curtis L. Brown, Jr., pilot; Mario Runco, Jr., mission specialist; Andrew S. W. Thomas, mission specialist; and Marc Garneau, mission specialist representing the Canadian Space Agency (CSA). The Space Shuttle Endeavour is undergoing preparations at Pad 39B for liftoff on the fourth Shuttle flight of 1996 around May 16, 1996.

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. -- STS-120 Pamela Melroy (front) is ready for training on the M-113 armored personnel carrier, part of emergency egress training. The training is part of terminal countdown demonstration test, or TCDT, activities the crew is undertaking at NASA's Kennedy Space Center. The TCDT also includes equipment familiarization and a simulated launch countdown. Mission STS-120, which will carry the Italian-built U.S. Node 2 to the International Space Station, is targeted for launch on Oct. 23. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. -- STS-120 Mission Specialist Doug Wheelock tries on his launch and entry suit to prepare for launch. The fitting is part of terminal countdown demonstration test, or TCDT, activities the crew is undertaking at NASA's Kennedy Space Center. The TCDT also includes emergency egress procedures, equipment familiarization and a simulated launch countdown. Mission STS-120, which will carry the Italian-built U.S. Node 2 to the International Space Station, is targeted for launch on Oct. 23. Photo credit: NASA/Kim Shiflett

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. -- STS-120 Mission Specialist Stephanie Wilson tries on her launch and entry suit, preparing for launch. The fitting is part of terminal countdown demonstration test, or TCDT, activities the crew is undertaking at NASA's Kennedy Space Center. The TCDT also includes emergency egress procedures, equipment familiarization and a simulated launch countdown. Mission STS-120, which will carry the Italian-built U.S. Node 2 to the International Space Station, is targeted for launch on Oct. 23. 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. - Inside Atlantis' cockpit, STS-115 Mission Specialists Daniel Burbank (front) and Steven MacLean, are taking part in a simulated launch countdown, the culmination of Terminal Countdown Demonstration Test activities. 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.

KENNEDY SPACE CENTER, FLA. - Inside Atlantis' cockpit, STS-115 Mission Specialists Heidemarie Stefanyshyn-Piper and Joseph Tanner are taking part in a simulated launch countdown, the culmination of Terminal Countdown Demonstration Test activities. 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.

KENNEDY SPACE CENTER, FLA. - Inside Atlantis' cockpit, STS-115 Pilot Christopher Ferguson is taking part in a simulated launch countdown, the culmination of Terminal Countdown Demonstration Test activities. 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.

KENNEDY SPACE CENTER, FLA. - Inside Atlantis' cockpit, STS-115 Commander Brent Jett is taking part in a simulated launch countdown, the culmination of Terminal Countdown Demonstration Test activities. 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.

S90-40670 (13 June 1990) --- STS-35 crewmembers take a ride in the M113 tracked vehicle during emergency training conducted during the Terminal Countdown Demonstration Test (TCDT) at the Kennedy Space Center (KSC). From left, wearing launch and entry suits (LES), are pilot Guy S. Gardner, payload specialist Ronald A. Parise, commander Vance D. Brand, mission specialists Robert A. R. Parker, Jeffrey A. Hoffman and John M. Lounge. The two-day TCDT, which began 04-27-90, is a dress rehearsal for launch. STS-35 is set to lift off in May. View provided by KSC with alternate number KSC-90PC-838.

CAPE CANAVERAL, Fla. -- After their arrival at the NASA Kennedy Space Center Shuttle Landing Facility, STS-124 Pilot Ken Ham (center) and Commander Mark Kelly (right) head for the runway to practice space shuttle landings using NASA's Shuttle Training Aircraft, or STA. The STA is a Grumman American Aviation-built Gulf Stream II jet that was modified to simulate an orbiter's cockpit, motion and visual cues, and handling qualities. In flight, the STA duplicates the orbiter's atmospheric descent trajectory from approximately 35,000 feet altitude to landing on a runway. Because the orbiter is unpowered during re-entry and landing, its high-speed glide must be perfectly executed the first time. The crew for space shuttle Discovery's STS-124 mission is at Kennedy for a full launch dress rehearsal, known as the terminal countdown demonstration test, or TCDT. Providing astronauts and ground crews with an opportunity to participate in various simulated countdown activities, TCDT includes equipment familiarization and emergency training. Discovery's launch is targeted for May 31. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-124 Commander Mark Kelly sits in the cockpit of NASA's Shuttle Training Aircraft, or STA, preparing to practice space shuttle landings. The STA is a Grumman American Aviation-built Gulf Stream II jet that was modified to simulate an orbiter's cockpit, motion and visual cues, and handling qualities. In flight, the STA duplicates the orbiter's atmospheric descent trajectory from approximately 35,000 feet altitude to landing on a runway. Because the orbiter is unpowered during re-entry and landing, its high-speed glide must be perfectly executed the first time. The crew for space shuttle Discovery's STS-124 mission is at Kennedy for a full launch dress rehearsal, known as the terminal countdown demonstration test, or TCDT. Providing astronauts and ground crews with an opportunity to participate in various simulated countdown activities, TCDT includes equipment familiarization and emergency training. Discovery's launch is targeted for May 31. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. -- STS-120 Mission Specialist Doug Wheelock has his helmet fitted on his launch and entry suit, preparing for launch. The fitting is part of terminal countdown demonstration test, or TCDT, activities the crew is undertaking at NASA's Kennedy Space Center. The TCDT also includes emergency egress procedures, equipment familiarization and a simulated launch countdown. Mission STS-120, which will carry the Italian-built U.S. Node 2 to the International Space Station, is targeted for launch on Oct. 23. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. - Following the mock countdown and emergency egress practice from the Fixed Service Structure on Launch Pad 39B, STS-114 crew members stop at the 225-foot level for a unique view. Seen here is Pilot James Kelly. This culminates the pre-launch training known as Terminal Countdown Demonstration Test (TCDT) activities. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

KENNEDY SPACE CENTER, FLA. - Following the mock countdown on Launch Pad 39B, STS-114 Commander Eileen Collins (center) adjusts her glove before climbing into a slidewire basket used for emergency egress from the Fixed Service Structure at the pad. This is part of the pre-launch training included in Terminal Countdown Demonstration Test (TCDT) activities. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

KENNEDY SPACE CENTER, FLA. - Following the mock countdown on Launch Pad 39B, STS-114 Mission Specialists Soichi Noguchi (left) and Stephen Robinson climb into a slidewire basket used for emergency egress from the Fixed Service Structure at the pad. This is part of the pre-launch training included in Terminal Countdown Demonstration Test (TCDT) activities. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

KENNEDY SPACE CENTER, Fla. -- In the slidewire basket bunker area of Launch Pad 39A, STS-118 Mission Specialist Dave Williams is introduced to the press during a media interview before the crew's morning training activities in the terminal countdown demonstration test, or TCDT. Williams represents the Canadian Space Agency. TCDT activities include M-113 training, payload familiarization, the emergency egress training at the pad and a simulated launch countdown. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. Photo credit: NASA/Ken Thornsley

KENNEDY SPACE CENTER, FLA. -- STS-120 Mission Specialist Doug Wheelock gets ready in the driver's seat for driving practice in the M-113 armored personnel carrier. The M-113 is part of emergency exit procedures from Launch Pad 39A. Behind him, at right, is Pilot George Zamka. The training is part of terminal countdown demonstration test, or TCDT, activities the crew is undertaking at NASA's Kennedy Space Center. The TCDT also includes equipment familiarization and a simulated launch countdown. Mission STS-120, which will carry the Italian-built U.S. Node 2 to the International Space Station, is targeted for launch on Oct. 23. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, Fla. -- On the slidewire basket bunker area of Launch Pad 39A, STS-118 Commander Scott Kelly talks to the media before the crew's morning training activities in the terminal countdown demonstration test, or TCDT. TCDT activities include M-113 training, payload familiarization, the emergency egress training at the pad and a simulated launch countdown. The mission is the 22nd flight to the International Space Station and Space Shuttle Endeavour will carry a payload including the S5 truss, a SPACEHAB module and external stowage platform 3. STS-118 is targeted for launch on Aug. 7. NASA/George Shelton

KENNEDY SPACE CENTER, FLA. - Following the mock countdown on Launch Pad 39B, STS-114 Pilot James Kelly adjusts his glove before climbing into a slidewire basket used for emergency egress from the Fixed Service Structure at the pad. This is part of the pre-launch training included in Terminal Countdown Demonstration Test (TCDT) activities. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

KENNEDY SPACE CENTER, FLA. - STS-114 crew members take part in a mock countdown as pre-launch training included in Terminal Countdown Demonstration Test (TCDT) activities. Seen here in their seats in the mid-deck of Space Shuttle Discovery are (left to right), Mission Specialists Charles Camarda, Wendy Lawrence and Andrew Thomas. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

KENNEDY SPACE CENTER, FLA. - Following the mock countdown and emergency egress practice from the Fixed Service Structure on Launch Pad 39B, STS-114 crew members stop at the 225-foot level for a unique view. Seen here is Mission Specialist Wendy Lawrence. This culminates the pre-launch training known as Terminal Countdown Demonstration Test (TCDT) activities. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

KENNEDY SPACE CENTER, FLA. - Following the mock countdown on Launch Pad 39B, STS-114 Mission Specialist Charles Camarda reaches for the release of the slidewire basket, used for emergency egress from the Fixed Service Structure. Behind him are Mission Specialists Andrew Thomas and Wendy Lawrence. This is part of the pre-launch training included in Terminal Countdown Demonstration Test (TCDT) activities. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

KENNEDY SPACE CENTER, FLA. -- STS-120 Pamela Melroy is ready for training on the M-113 armored personnel carrier, part of emergency egress training. Behind her Mission Specialist Paolo Nespoli looks on. Nespoli is with the European Space Agency. The training is part of terminal countdown demonstration test, or TCDT, activities the crew is undertaking at NASA's Kennedy Space Center. The TCDT also includes equipment familiarization and a simulated launch countdown. Mission STS-120, which will carry the Italian-built U.S. Node 2 to the International Space Station, is targeted for launch on Oct. 23. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, Fla. -- STS-118 Commander Scott Kelly stands inside an M-113 armored personnel carrier before his driving session as part of emergency exit training. He and other crew members are at Kennedy for the Terminal Countdown Demonstration Test (TCDT), a dress rehearsal for launch. TCDT activities include the M-113 training, payload familiarization, emergency egress training at the pad and a simulated launch countdown. The STS-118 payload aboard Space Shuttle Endeavour includes the S5 truss, a SPACEHAB module and external stowage platform 3. The mission is the 22nd flight to the International Space Station and is targeted for launch on Aug.7. NASA/George Shelton

KENNEDY SPACE CENTER, FLA. - Following the mock countdown on Launch Pad 39B, STS-114 Commander Eileen Collins talks to Pilot James Kelly at the slidewire basket area used for emergency egress from the Fixed Service Structure at the pad. This is part of the pre-launch training included in Terminal Countdown Demonstration Test (TCDT) activities. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

KENNEDY SPACE CENTER, FLA. - Following the mock countdown on Launch Pad 39B, STS-114 Mission Specialist Stephen Robinson (left) and Soichi Noguchi talk at the slidewire basket area used for emergency egress from the Fixed Service Structure at the pad. This is part of the pre-launch training included in Terminal Countdown Demonstration Test (TCDT) activities. TCDT provides the crew of each mission an opportunity to participate in various simulated countdown activities, including equipment familiarization and emergency egress training. STS-114 is the first Return to Flight mission to the International Space Station. The launch window extends July 13 through July 31.

KENNEDY SPACE CENTER, FLA. -- STS-120 Commander Pamela Melroy is ready for her turn at driving practice in the M-113 armored personnel carrier. The M-113 is part of emergency exit procedures from Launch Pad 39A. The training is part of terminal countdown demonstration test, or TCDT, activities the crew is undertaking at NASA's Kennedy Space Center. The TCDT also includes equipment familiarization and a simulated launch countdown. Mission STS-120, which will carry the Italian-built U.S. Node 2 to the International Space Station, is targeted for launch on Oct. 23. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, FLA. -- STS-120 Mission Specialist Paolo Nespoli has his helmet fitted on his launch and entry suit, preparing for launch. The fitting is part of terminal countdown demonstration test, or TCDT, activities the crew is undertaking at NASA's Kennedy Space Center. The TCDT also includes emergency egress procedures, equipment familiarization and a simulated launch countdown. Mission STS-120, which will carry the Italian-built U.S. Node 2 to the International Space Station, is targeted for launch on Oct. 23. Photo credit: NASA/Kim Shiflett

KENNEDY SPACE CENTER, Fla. -- STS-118 Commander Scott Kelly practices driving an M-113 armored personnel carrier with fellow crew members Tracy Caldwell, Alvin Drew and Dave Williams, all mission specialists, as passengers. They are at Kennedy for the Terminal Countdown Demonstration Test (TCDT), a dress rehearsal for launch. TCDT activities include the M-113 training, payload familiarization, emergency egress training at the pad and a simulated launch countdown. The STS-118 payload aboard Space Shuttle Endeavour includes the S5 truss, a SPACEHAB module and external stowage platform 3. The mission is the 22nd flight to the International Space Station and is targeted for launch on Aug.7. NASA/George Shelton

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