(Third Space Flight)

(First Space Flight) Mission Specialist 1:

(Second Space Flight) Mission Specialist 2:

(Fifth Space Flight) Mission Specialist 3:

(First Space Flight) Mission Specialist 4:

Paolo A. Nespoli, ESA

(Second Space Flight) ISS Flight Engineer -
Exp. 16 -MS-5

(First Space Flight) ISS Flight Engineer - Exp. 16 -MS- 5

Mission Specialist 4: Salizhan Sharipov, RKA (First Space Flight)

(First Space Flight)

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Pages within this section: USA Shuttle Mission Flights

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The Space Shuttle Missions

Crew Prior to Columbia
PositionAstronaut
CommanderJames D. Halsell
Sixth spaceflight
PilotAlan G. Poindexter
First spaceflight
Mission Specialist 1Wendy Lawrence
Fourth spaceflight
Mission Specialist 2Stephanie Wilson
First spaceflight
Mission Specialist 3Piers Sellers
Second spaceflight
Mission Specialist 4Michael Foreman
First spaceflight

In light of the small gouge to the underside of Endeavour that occurred on STS-118, in August 2007, NASA managers announced that they expected to add a fifth spacewalk to the STS-120 mission, designed to test a heat-shield repair tool. The repair technique was originally scheduled for a flight in 2008, but following STS-118, it was decided to move up the testing. The repair tool, called a TPS (thermal protection system) repair ablator dispenser (T-RAD), has never been tested in space, so the spacewalk would have allowed managers to evaluate its effectiveness in low gravity environments.During the course of the mission, issues with the S4 starboard Solar Alpha Rotary Joint (SARJ), and P6 Solar Array, deferred this test objective to a future mission.

Following STS-118 in August 2007, NASA managers decided to make modifications to the external tank to be used on STS-120, and modify the liquid oxygen feed-line brackets. The change involved a new low-density foam application, and thinner gaskets. Shuttle Program Managers decided to do this to reduce the foam loss from the area that had been noted since STS-114's "Return to Flight" mission in 2005. STS-118 had a small gouge on the belly of the orbiter due to a chunk of foam that impacted during launch in August 2007. The week of 17 September 2007, NASA managers decided to delay Discovery's rollover to the Vehicle Assembly Building (VAB), due to a hydraulic fluid leak from the right main landing gear strut. The strut repair was successfully completed on 19 September 2007. Discovery then moved to the VAB, and was mated to the External Tank and Solid Rocket Boosters. Perched atop the mobile launcher platform, Discovery arrived at Launch complex 39A on 30 September 2007.

The crew of STS-120 arrived at Kennedy Space Centre on 7 October 2007 and began final preparations, including the terminal countdown demonstration test, or "Dress Rehearsal", scheduled for 7 October 2007 through 10 October 2007.

On 9 October 2007, NASA's Engineering and Safety Center, an independent review group set up after the 2003 Columbia disaster, advised replacement of three of Discovery's reinforced carbon-carbon (RCC) panels on the leading wing edge, due to a loss of small amounts of the protective silicon-carbide coating. NASA reviewed the issue of oxidation of the panels for several months, using a variety of specialized testing methods, including thermography.These tests showed that the panels had not worsened over the course of the past two flights of Discovery, and the orbiter project engineers concluded in August that Discovery was safe to launch as is.Had a decision been made to repair the panels, the orbiter would have been rolled back to the VAB, delaying the launch.

On 16 October 2007, NASA Managers completed the Flight Readiness Review, and held a press conference to announce the mission plan.[32] The issue of the RCC panels raised by NESC was found to be of little immediate concern, because the NESC took pre-flight thermography data from Endeavour and compared it with Discovery, but there was no commonality in flight history between the two vehicles. The research showed no significant difference between the panels prior to STS-114, and the panels today, which indicates the coating has not worsened during the previous flights, adding confidence that Discovery's RCC panels have had no deterioration in the flights since. NASA announced on the main shuttle page that "The Space Shuttle Program has determined that Discovery's astronauts can safely carry out their mission without having to replace the panels.

At the time of the Columbia disaster, STS-120 was scheduled for early 2004. It was delayed repeatedly until 23 October 2007.

NASA originally scheduled the launch for 20 October 2007, but due to the International Space Station program requirement, launch was delayed to 23 October 2007.