[4] Together they represented all ISS program partners[5] and tied the general record of thirteen people in space with the first such occurrence of 1995.

[7][8] The Ground Umbilical Carrier Plate (GUCP) on the external fuel tank experienced a potentially hazardous hydrogen gas leak similar to the fault that delayed the Space Shuttle Discovery mission STS-119 in March 2009.

[NASA 2][12] A successful tanking test for leak checks was performed on July 1, 2009, with modified GUCP seals allowing launch preparations to proceed as scheduled.

[16] Endeavour carried a wide variety of equipment and cargo in the payload bay, with the largest item being the Kibō Japanese Experiment Module Exposed Facility (JEM EF), and the Kibō Japanese Experiment Logistics Module – Exposed Section (ELM-ES).

Also inside the payload bay was an Integrated Cargo Carrier-Vertical Light Deployable (ICC-VLD), containing a variety of equipment and spare components for the station.

A set of experiments to be deployed on the ISS were carried by STS-127, including 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).

[19] The docking module was also mounted with the DragonEye 3D Flash LIDAR ranging system manufactured by Advanced Scientific Concepts, Inc.

The module was launched to test the docking system which will be used by the commercial SpaceX Dragon re-usable cargo carrier to send supplies to the ISS during the post-shuttle era.

[22][NASA 7] The crew of STS-127 arrived at Kennedy Space Center on June 2, 2009, for the Terminal Countdown Demonstration Test (TCDT) that concluded with a full launch dress rehearsal.

[11] Following the launch scrub, Chairman of NASA's Mission Management Team LeRoy Cain noted that engineers would work to understand the hydrogen leak issue and come up with a solution to the problem.

[25] On July 1, 2009, the shuttle managers conducted a new series of tanking tests to confirm a hypothesis that a misaligned vent port housing was the root cause of the leaks.

The existing rigid seal was replaced with a flexible one in the hope that it would maintain a tight fix even under the cryogenic conditions that seem to cause the leak.

During the final Go/No-Go polls, Mission Control in Houston declared a "No-Go" due to unacceptable weather forecast for a possible Return-To-Launch-Site (RTLS) abort, and planned for emergency scenarios when one or more engines shut down early leaving insufficient energy to reach the Transatlantic Abort Landing (TAL) sites.

[34] Upon reviewing the launch video footage, imagery analysts noted eight or nine instances of foam shedding from the External Tank.

[36] The chairman of the Mission Management Team was not concerned and felt that the Space Shuttle would be cleared for re-entry on its return voyage—which it was a few days later.

[37][38][NASA 11] The payload doors were opened after reaching orbit followed by deployment of the Ku band antenna and activation of the shuttle's mechanical arm.

The extravehicular mobility units were checked in addition to the rendezvous system tests and centerline camera installation.

[39][NASA 12] The shuttle successfully docked with the station 220 miles (350 km) above the Earth, following rendezvous pitch maneuver (RPM) photography of Endeavour's thermal protection system by the Expedition 20 Crew.

The docking happened on the ISS's PMA-2 (Pressurized Mating Adapter) on the Harmony module and the hatch was opened after leak checks.

[15] EVA 1 started with astronauts Dave Wolf and Tim Kopra switching their spacesuit power to internal battery at 16:19 UTC.

A malfunction in a new toilet in the Destiny laboratory caused the crew to use the one in the Russian segment while attempts were made to identify the fault.

The spares were handled by Wolf riding the station's robotic arm to the P3 truss stowage platform where he and Marshburn attached them for long-term storage.

The spares unloaded include a Ku-Band Space-to-Ground antenna, a pump module for the coolant system and a drive unit for the station's robotic arm's mobile transporter.

After the experiments, containing an X-ray astronomy payload, a space environment monitor and a communications system, are installed the pallet will be returned to Earth by the shuttle.

Meanwhile, Wolf removed obstructions, consisting of a steel handrail and an equipment installation socket, from the Harmony node to clear the way for an upcoming Japanese automated resupply ship.

The three experiments, transferred from the Japanese cargo pallet, consisted of Monitor of All-sky X-ray Image, Inter-orbit Communication System and Space Environment Data Acquisition Equipment-Attached Payload.

After berthing the old batteries in the ICC-VLD, the cargo pallet was returned to the Endeavour's payload bay by the shuttle's robotic arm.

[NASA 23][61][62] Cassidy and Marshburn started EVA 5 at 11:33 UTC when they switched their suit power to internal battery.

For this spacewalk, the CO2 absorbent system in the suits were changed from Lithium Hydroxide to METOX due to problems with Cassidy's usage.

[NASA 25][67][68] The OBSS was grappled by the shuttle's robotic arm and used to inspect Endeavour's thermal protection system for damage from orbital debris.