
KENNEDY SPACE CENTER, FLA. -- Technicians at Pad 39-B carry a new Auxiliary Power Unit (APU) to be installed in the orbiter Discovery. It will replace APU #1 that failed during the STS-31 launch attempt on April 10.

KENNEDY SPACE CENTER, FLA. -- Technicians install a new Auxiliary Power Unit (APU) in the aft compartment of the orbiter Discovery at Pad 39-B. The unit replaces APU #1 that failed during the STS-31 countdown on April 10.

A mechanical arm positions the axial scientific instrument (SI) module (orbital replacement unit (ORU)) just outside the open doors of the Hubble Space Telescope (HST) Support System Module (SSM) as clean-suited technicians oversee the process. HST assembly is being completed at the Lockheed Facility in Sunnyvale, California.

KENNEDY SPACE CENTER, FLA. -- A new Enhanced Main Events Controller (E-MEC) for Shuttle Endeavour sits on a table in a Quality trailer in the Launch Pad 39B area. The original E-MEC in Endeavour became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. The E-MECs are located in the orbiter's aft compartment and both are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. Before workers can begin E-MEC replacement efforts at the launch pad, cryogenic reactants must be offloaded from the orbiter and Space Shuttle ordnance disconnected. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- Workers in a Quality trailer in the Launch Pad 39B Area unwrap a new Enhanced Main Events Controller (E-MEC) to be installed in Shuttle Endeavour. The original E-MEC in Endeavour became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. The E-MECs are located in the orbiter's aft compartment and both are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. Before workers can begin E-MEC replacement efforts at the launch pad, cryogenic reactants must be offloaded from the orbiter and Space Shuttle ordnance disconnected. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- Workers in a Quality trailer in the Launch Pad 39B Area unwrap a new Enhanced Main Events Controller (E-MEC) to be installed in Shuttle Endeavour. The original E-MEC in Endeavour became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. The E-MECs are located in the orbiter's aft compartment and both are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. Before workers can begin E-MEC replacement efforts at the launch pad, cryogenic reactants must be offloaded from the orbiter and Space Shuttle ordnance disconnected. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- A new Enhanced Main Events Controller (E-MEC) for Shuttle Endeavour sits on a table in a Quality trailer in the Launch Pad 39B area. The original E-MEC in Endeavour became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. The E-MECs are located in the orbiter's aft compartment and both are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. Before workers can begin E-MEC replacement efforts at the launch pad, cryogenic reactants must be offloaded from the orbiter and Space Shuttle ordnance disconnected. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- Technicians work in the aft compartment of Shuttle Endeavour's payload bay, where a new Enhanced Main Events Controller (E-MEC) will be installed. The original E-MEC in Endeavour became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. Both E-MECs are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. Before workers can begin E-MEC replacement efforts at the launch pad, cryogenic reactants had to be offloaded from the orbiter and Space Shuttle ordnance disconnected. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- Technicians work in the aft compartment of Shuttle Endeavour's payload bay, where a new Enhanced Main Events Controller (E-MEC) will be installed. The original E-MEC in Endeavour became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. Both E-MECs are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. Before workers can begin E-MEC replacement efforts at the launch pad, cryogenic reactants had to be offloaded from the orbiter and Space Shuttle ordnance disconnected. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 39A, workers move the replacement Enhanced Main Events Controller (E-MEC) into Shuttle Endeavour's aft compartment in the payload bay. The original E-MEC became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. Both E-MECs are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- Workers carry the replacement Enhanced Main Events Controller (E-MEC) to Shuttle Endeavour at Launch Pad 39A for installation in the aft compartment of the payload bay. The original E-MEC became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. Both E-MECs are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- Workers carry the replacement Enhanced Main Events Controller (E-MEC) to Shuttle Endeavour at Launch Pad 39A for installation in the aft compartment of the payload bay. The original E-MEC became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. Both E-MECs are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 39A, workers move the replacement Enhanced Main Events Controller (E-MEC) into Shuttle Endeavour's aft compartment in the payload bay. The original E-MEC became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. Both E-MECs are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- Technicians remove a faulty Enhanced Main Events Controller (E-MEC) from Shuttle Endeavour at Launch Pad 39A. The E-MEC became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. Both E-MECs are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- Workers carry away the faulty Enhanced Main Events Controller (E-MEC) from Shuttle Endeavour at Launch Pad 39A. The E-MEC became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. Both E-MECs are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- Technicians remove a faulty Enhanced Main Events Controller (E-MEC) from Shuttle Endeavour at Launch Pad 39A. The E-MEC became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. Both E-MECs are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST

KENNEDY SPACE CENTER, FLA. -- Workers carry away the faulty Enhanced Main Events Controller (E-MEC) from Shuttle Endeavour at Launch Pad 39A. The E-MEC became suspect during the Jan. 31 launch countdown and mission STS-99 was delayed when NASA managers decided to replace it. Each Shuttle carries two enhanced master events controllers (E-MECs), which provide relays for onboard flight computers to send signals to arm and fire pyrotechnics that separate the solid rockets and external tank during assent. Both E-MECs are needed for the Shuttle to be cleared for flight. Currently Endeavour and Columbia are the only two orbiters with the E-MECs. Built by Rockwell's Satellite Space Electronics Division, Anaheim, Calif., each unit weighs 65 pounds and is approximately 20 inches long, 13 inches wide and 8 inches tall. Previously, three Shuttle flights have been scrubbed or delayed due to faulty MECs: STS-73, STS-49 and STS-41-D. The next scheduled date for launch of STS-99 is Feb. 11 at 12:30 p.m. EST