Launch from Cape Canaveral (KSC); landing on the Edwards AFB; ISS-17A MPLM Leonardo, LMC.

Due to bad weather in Florida (August 25, 2009) and technical problems (August 26, 2009) the launch was delayed three times.

The mission of Christer Fuglesang is named Alissé by the European Space Agency. The name was proposed by Jürgen Modlich from Baierbrunn, Germany. The name refers to the 15th-century explorers who used the trade winds to follow Christopher Columbus across the oceans to the New World.

Following a two day solo flight Discovery docked to the ISS on August 31, 2009. Shuttle commander Frederick "C.J." Sturckow, forced by a leaky steering jet to use Discovery's big maneuvering thrusters instead of preferred fine-control vernier engines.

Joint operations with the ISS expedition 20 were performed. Nicole Stott was transferred to the ISS and Timothy Kopra to the STS-128 crew for returning to the Earth. The primary payload is the Multi-Purpose Logistics Module Leonardo, containing a collection of experiments for studying the physics and chemistry of microgravity. Three spacewalks are planned during the mission, which will remove and replace a materials processing experiment outside ESAs Columbus module, and to return an empty ammonia tank assembly.

Nicole Stott was originally scheduled to return aboard Soyuz TMA-15, but a change in the flight plan was made due to the possible flight delays in future shuttle missions, which may extend Canadian astronaut Robert Thirsks mission beyond the six-month duration preferred for station crew members.

The first EVA by John Olivas and Nicole Stott occured on September 01, 2009 (6h 35m) to prepare for the replacement of an empty ammonia tank on the station's port truss, or backbone, by releasing its bolts. They also retrieved a materials processing experiment (MISSE) and a European science experiment (EuTEF) mounted outside the Columbus laboratory and stowed them in Discovery's cargo bay for their return to Earth.

In between research facilities were tranferred from Leonardo to Destiny.

The second EVA was performed by John Olivas and Christer Fuglesang on September 03, 2009 (6h 39m) to remove the new ammonia tank from the shuttle's payload bay and replacing it with the used tank on the station. The new tank, weighing about 1,800 pounds, was the most mass ever moved around by spacewalking astronauts. After the new tank was installed, the old one was stowed in the shuttle for its return to Earth. On Earth the tank will be refueled and delivered again to the ISS during the mission of STS-131.

The third and final EVA by John Olivas and Christer Fuglesang was conducted on September 05, 2009 (7h 01m) to prepare for the arrival of the Tranquility node by attaching two 18m long cables between the starboard truss and the Unity node, the area where Tranquility will be installed. Tranquility is targeted to arrive to the station on STS-130 in February 2010. The spacewalkers also replaced a communications sensor device, installed two new GPS antennas and a new circuit breaker.

The STS-128 mission (as did STS-125 and STS-127) took part in crew seat vibration tests that will help engineers on the ground understand how astronauts experience launch. They will then use the information to help design the crew seats that will be used in future NASA spacecraft.

STS-128 repeated the Boundary Layer Transition (BLT) Detailed Test Objective (DTO) experiment that was done by the same shuttle during STS-119. In this experiment, one of the thermal protection systems was raised to create a boundary layer transition in which the air flow becomes turbulent beyond a certain speed. During STS-119 the tile was raised 0.25 inches (6.4 mm) above the others, tripping the flow at Mach 15, 2009 during reentry. In the modification being done, the tile has been raised 0.35 inches (8.9 mm) to trip at Mach 18 producing more heat.

Discovery undertook the testing of a catalytic coating which was meant to be used by the Orion (spacecraft). Two TPS tiles located in the protuberance downstream from the BLT tile had been fully coated with the catalytic material in order to understand the entry heating performance. The tiles were instrumented to collect a wide variety of data

The first two landing opportunities were postponed for one day due to weather conditions. After weather didn't get better in Florida, Discovery had to land on Edwards AFB.

Nicole Stott landed on November 27, 2009 at 14:44 UTC with STS-129.