Launch from Cape Canaveral (KSC); landing at Cape Canaveral (KSC); ISS-2J/A JEM EF, JEM ELM-ES.

Originally the launch was planned for June 13, 2009. NASA cancelled the launch attempt of the Endeavour because of a leak in the gaseous hydrogen vent system. The same problem forced to scrub a second launch attempt on June 17, 2009. Running a month late because of hydrogen leaks and stormy weather, the shuttle Endeavour finally blasted off on its sixth try.

Following a two day solo flight Endeavour docked to the ISS on July 17, 2009. Joint operations with the ISS expedition 20 followed. Timothy Kopra was transferred to the ISS and Koichi Wakata to the STS-127 crew for returning to the Earth. The main goal of this mission was to deliver and install the third and the last piece the Japanese Exposed Facility (JEM EF) to Kibo and the Kibo Japanese Experiment Logistics Module - Exposed Section (JEM ELM-ES). The exposed facility (a kind of "porch") is a part of Kibo that will allow astronauts to perform science experiments that are exposed to the vacuum of space. The exposed section is similar to the logistics module on the Kibo laboratory, but is not pressurized. Once its payloads are transferred to the JEM EF, the JEM ELM-ES will be returned to the payload bay.

Two satellites were also carried by the orbiter, for deployment when the mission ended. The Dual Autonomous Global Positioning System On-Orbit Navigator Satellite, called DRAGONSAT, gathered data on autonomous spacecraft rendezvous and docking capabilities, and consists of two picosatellites, the AggieSat2, and PARADIGM (BEVO-1), which acquire GPS data from a device at NASA and send it to ground stations at Texas A&M University and the University of Texas at Austin.After release, the two picosatellites remained attached for two orbits to collect GPS data, and separate during the third orbit.

A second satellite, the Atmospheric Neutral Density Experiment (ANDE-2), is part of a United States Department of Defense project flown by the Naval Research Laboratory to provide high-quality satellites, and will measure the density and composition of the low Earth orbit atmosphere while being tracked from the ground, to better predict the movement and decay of objects in orbit. ANDE-2 consists of two spherical microsatellites, ANDE Active spacecraft (Castor) and the ANDE Passive spacecraft (Pollux), and will be tracked by the International Laser Ranging Service (ILRS) network as well as the Space Surveillance Network (SSN).One of the satellites, Pollux, is running Arduino libraries, with its payload programmed and built by students.

A set of experiments to be deployed on the ISS were carried by STS-127, namely Dosimetry for Biological Experiments in Space (ESA), Validation of Procedures for Monitoring Crew Member Immune Function, the student-made Image Reversal in Space (CSA/ISU), Nutritional Status Assessment (NASA), NASA Biological Specimen Repository and Tomatosphere-II (CSA).

The first EVA by David Wolf and Timothy Kopra occured on July 18, 2009 (5h 32m) to prepare connecting mechanisms for Kibo and the exposed facility, which the station's robotic arm installed later in the day. They also released bolts on an ammonia tank assembly as get-ahead work for the next shuttle mission, STS-128. Then, both worked to deploy the unpressurized cargo carrier attachment system (UCCAS) on the Port 3 truss that was jammed and couldn't be done on STS-119. The UCCAS will be used in the future to store equipment and supplies on the outside of the station.

The second EVA was performed by David Wolf and Thomas Marshburn on July 20, 2009 (6h 53m) to transport of spare parts from a cargo carrier to a stowage platform on the station's truss. These parts include: an antenna, a pump module and a rail mechanism that allows a transporter to move up and down the truss. They also relocated a grapple bar onto an ammonia tank assembly as a get-ahead for the STS-129 mission, targeted for November 2009. A planned installation of a camera on the Japanese Experiment Facility was postponed to a future EVA for want of time.

The third EVA by David Wolf and Christopher Cassidy was conducted on July 22, 2009 (5h 59m) to prepare the exposed facility for experiment transfers and replace two out of the six batteries (four were planned) on the port side truss where they are housed to provide power for the truss. This EVA was shortened by NASA managers when astronaut Christopher Cassidys carbon dioxide levels showed an upward trend due to a problem with his spacesuit's CO2 removal system. The calling off the spacewalk was simply a precaution.

The fourth EVA was performed by Thomas Marshburn and Christopher Cassidy on July 24, 2009 (7h 12m) to replace the final four batteries on the port truss.

The fifth and final EVA by Thomas Marshburn and Christopher Cassidy occured on July 27, 2009 (4h 54m) to remove covers from the Dextre robotic arm, reconfigure cables on a panel for some circuit breakers and deploy two additional payload attachment systems. They also installed a second camera that will provide video of experiments on the aft end of the exposed facility, a work, which was originally scheduled for EVA 4. Finally, they replaced an aging camera system on the starboard truss. Instead some get ahead tasks were completed which included installation of handrails and a portable foot restraint.

Timothy Kopra landed on September 12, 2009 at 00:53 UTC with STS-128.