The Space Shuttle fleet is due to be retired by the end of this year, but the youngest shuttle still has two more missions to complete. Both of these will be assembly missions to the International Space Station. Endeavour was constructed as a replacement vehicle after the Challenger disaster in 1986.

The STS-130 mission launched successfully this morning carrying two primary payloads weighing more than 16.5 tons. The Tranquility module was built by Thales Alenia and funded by the European Space Agency. It houses some of the most advanced life support systems in space, in particular waste water recyclers (up to 93% efficient), oxygen generators, and CO2 scrubbers.

Tranquility is an evolutionary design building upon the experience of constructing Node 1 (Unity) and Node 2 (Harmony). It contains an extensive piping network for the distribution of water (for fuel cells, drinking, waste and processes) between itself and Node 1. There is a special line for the transfer of pretreated urine from a new Waste and Hygiene Compartment (otherwise known as a toilet) to Water Recovery System racks inside Node 3. Special lines and sectioning devices are also adapted to distribute oxygen and nitrogen.

Originally designated as Node 3, Tranquility was named after NASA held a controversial online poll. NASA wanted the public to give their input on the suggested names: Earthrise, Legacy,Serenity, and Venture. However, they allowed the public to suggest their own write-in names. Stephen Colbert suggested naming it after himself on his TV show, and a race developed with the fans of the Serenity movie, named after the spacecraft from the Firefly TV series.

Almost 1.2 million votes were cast, but Colbert won by 40,000 votes. However, NASA had reserved the right to pick the final name, and choose Tranquility in honor of the 40th anniversary of the Apollo 11 lunar landing on the Sea of Tranquility. The COLBERT (Combined Operational Load Bearing External Resistance Treadmill) was named instead for Colbert. It was launched in September of last year and temporarily installed in Node 2, but will be moved to its permanent location in Tranquility after it is attached to the ISS.

The Cupola is a pressurized observation and work area that will accommodate command and control workstations and other hardware. It will primarily be used to control station robotics such as the Canadarm2, Dextre, and the European Robotic Arm. However, it will also be uses as a 360 degree observation station by ISS astronauts. There aren't a lot of viewing stations on the ISS, which has mostly small portholes. The best view is currently afforded by a 20 inch (50 cm) window on the Destiny module. The cupola includes window shutters that provide orbital debris protection when closed.

There are also multiple experiments being carried onboard Endeavour. NLP-Vaccine-7 is a commercial payload serving as a pathfinder for the use of the ISS as a National Laboratory after station assembly is complete. It will use several different pathogenic organisms to further assess the use of space flight to develop potential vaccines for infections caused by these pathogens on Earth and in microgravity.

Several experiments will focus on the growth of plants in microgravity, including NLP-Cells-3. That experiment will verify the potential effects of microgravity on improving characteristics such as cell structure, growth, and development of the Jatropha curcas plant, which has the potential to be used as an alternative biofuel crop.

The ISS will be about 90 percent complete after the Tranquility module and the Cupola are installed. The next shuttle flight will be in March by Discovery to deliver more supplies and experiments. Endeavour's last flight will be in July, after which it will be decommissioned and likely sent to a museum.