The International Space Station orbiting the Earth has been under construction since 1998. Contributions from the US, Russia, Japan and Europe will continue to be added before its completion sometime after 2010.
The source of the station's power is the Sun - through its solar panels.
The first panels were taken into space in 2000 and were installed on the early external truss framework to provide power for the US-built Unity habitation module.
The station will eventually have four large sets. Each of their wing segments is 34m (112ft) long by 12m (39ft) wide; and capable of generating nearly 32.8 kW of direct current power.
Each solar array set has a wingspan of 73m (240ft) in total - longer than that of a Boeing 777 aeroplane (65m).
MOBILE SERVICING SYSTEM
The Mobile Servicing System plays a key role in assembly and maintenance of the space station. Its components can move equipment and supplies, support astronauts working in space and servicing instruments and other payloads attached to the space station.
It includes the robotic Canadarm2 which is used to carry out assembly operations. Astronauts can also be anchored to the 17.6m-long (57.7ft) arm to perform external work.
The arm was taken to the ISS onboard Space Shuttle Endeavour in 2001.
A work platform, or Mobile Base System, moves along rails across the space station, providing lateral mobility for the Canadarm2.
Future additions to the servicing system include a smaller two-armed robot called the Special Purpose Dexterous Manipulator - or Dextre. It is designed to carry out delicate assembly tasks currently performed by astronauts on spacewalks. Dextre is scheduled to launch on assembly flight 1J/A in 2007.
The module Zarya, which means Sunrise in Russian, was the first component launched for the International Space Station. The module, or Functional Cargo Block, was designed to provide the station's initial propulsion and power.
It was funded by the US but built and then launched by the Russians on a Proton rocket in November 1998. Space Shuttle Endeavour linked with the module and attached the US-built connecting module Unity.
Zarya provided orientation control, communications and electrical power before the launch of the Zvezda Service Module in 2000.
Zarya is now used mainly for its storage capacity and external fuel tanks.
The 19,300kg (42,550lb) pressurised module is 12.6m (41ft) by 4.1m (13ft) and has an operational lifetime of at least 15 years.
The Cupola will give astronauts fantastic views of Earth
Its solar arrays and six nickel-cadmium batteries can provide an average of 3 kW of electrical power.
Side docking ports enable the Russian Soyuz piloted spacecraft and unpiloted Progress resupply spacecraft to attach to the space station.
The Russian Zvezda module provides living quarters, life support, electrical power distribution, data processing, flight control and propulsion.
Zvezda, the Russian word for Star, also has a communications system that gives remote command capabilities to flight controllers on Earth. Many of the systems are being supplemented or replaced by US station components.
The module is similar in layout to the core module of Russia's old Mir Space
Living facilities on Zvezda include sleeping quarters for the crew; a toilet and hygiene facilities; a kitchen with a fridge-freezer; and a table for securing meals while eating. There is also exercise equipment including a treadmill and a stationary bicycle.
Zvezda has the primary docking port for the Progress supply craft.
The Progress resupply craft is an automated, unpiloted version of the Soyuz spacecraft used to take fuel and supplies to the space station. It can carry up to 1,700kg (3750lbs) of supplies and tanks that can hold up to 1,740kg (3840lbs) of fuel.
Progress normally takes two days to reach the space station and the rendezvous and docking are both automated.
It usually docks with the Zvezda module, but can dock elsewhere. Once docked, the space station crew enter the cargo module through the docking hatch.
The cargo is removed before the crew fill the craft with rubbish, unneeded equipment and waste water, which will all burn up with Progress when it re-enters the Earth's atmosphere over the Pacific Ocean.
Progress has the ability to alter the station's altitude and orientation using its thrusters.
The Russian Soyuz space capsule took the first crew to the International Space Station in November 2000. Since then, at least one Soyuz has always been at the space station to be used as an emergency "lifeboat" should the crew have to return to Earth unexpectedly.
After the Space Shuttle Columbia accident in 2003, the Soyuz became the only means of transportation for crew members going to or returning from the space station.
A new Soyuz capsule is normally delivered to the station by a Soyuz "taxi crew" every six months - the taxi crew then returns to Earth in the older Soyuz capsule.
The capsules are launched from the Baikonur Cosmodrome in Kazakhstan aboard a Soyuz rocket. After reaching orbit, it spends two days chasing the station before automatically docking. There is also the option for manual control by the crew.
Up to three crew members can launch and return to Earth in a Soyuz capsule.
The return journey takes less than 3.5 hours. The capsule lands in Kazakhstan.
Safety measures on Soyuz include custom-fitted liners for each crew member's seat. The moulded liners ensure a tight, comfortable fit when the module lands on the Earth. Crew take their seat liners with them to the space station.
The latest Soyuz TMA has less height restrictions than earlier versions. The maximum height is 1.9m tall (6ft 3in) and 94.8kg (209lb); the minimum crew member size is 1.5m (4ft 11in) and 50kg (110lb).
The US research laboratory Destiny was delivered to the space station by Space Shuttle Atlantis in 2001.
Crew members use it to carry out a wide range of experiments and studies, especially testing the physical effects of the absence of gravity. The laboratory includes experiment facilities such as the Microgravity Science Glovebox and the Human Research Facility. Eventually, Destiny will hold up to 13 telephone booth-sized racks with experiments in human life science, materials research, Earth observations and commercial applications.
Destiny's window takes up the space of one rack but enables the crew to take high quality photos and video. The images have been used by international scientists to study the Earth's features - such as glaciers, coral reefs, urban growth and wild fires.
Destiny, which is covered by a debris shield blanket made of a material similar to that used in bullet-proof vests, also contains the control centre for the Canadarm2 robotic arm operations.
Destiny will be joined by laboratory modules sponsored by the Japanese Aerospace Exploration Agency (Jaxa), European Space Agency (Esa) and the Russian Space Agency, Roskosmos.
The space shuttle was the world's first reusable spacecraft. It launches like a rocket, manoeuvres in orbit like a spacecraft and lands like an airplane. It is the only vehicle capable of delivering and returning large payloads and scientific experiments to and from space.
The first shuttle, Columbia, launched in April 1981.
Nasa's workhorse, the shuttle plays a vital role in building the International Space Station. It has deployed and visited the Hubble Space Telescope and deployed planetary spacecraft to study Jupiter, Venus and the Sun.
Hundreds of experiments have been carried out in the craft's onboard laboratories, helping scientists study the effects of microgravity.
The flight deck seats four. Each seat has manual flight controls and allows for a one-man emergency return. Displays and controls on the left operate the shuttle, and those on the right are for operating payloads. More than 2,020 separate displays and controls are located on the flight deck.
Each of the three space shuttle orbiters now in operation - Discovery, Atlantis and Endeavour - is designed to fly at least 100 missions.
Two shuttles have been lost - Challenger which was destroyed in an explosion shortly after lift-off in January 1986, and Columbia which was destroyed during re-entry in February 2003.
Crews have ranged from two members to eight - but most flights have between five and seven members on board.
JAPANESE EXPERIMENT MODULE (JEM)
The Japanese Experiment Module (JEM) is also known Kibo - which means "Hope" in Japanese.
It is Japan's first human space facility and will be the largest single module on the ISS. The module will enable up to four astronauts to carry out experiments in a pressurised laboratory.
Experiments in Kibo will focus on space medicine, biology, Earth observations, material production, biotechnology and communications research.
The pressurised part is 11.2m (36.7ft) long and 4.4m (14.4ft) in diameter.
Kibo experiments and systems are operated from the Mission Control Room at the Space Station Operations Facility at Tsukuba Space Centre, just north of Tokyo in Japan.
Kibo is made up of six components: two research facilities - the Pressurised Module and Exposed Facility; a logistics module attached to each of them; a remote manipulator system; and an inter-orbit communication system unit.
Kibo also has a scientific airlock through which experiments are transferred and exposed to the external environment of space. The Japan Aerospace Exploration Agency (Jaxa) plans to launch Kibo in 2008.
JEM EXPOSED FACILITY
The Exposed Facility of JEM, or Kibo, is located outside the pressurised module and is continuously exposed to the space environment.
Items positioned on the exterior platform focus on Earth observation as well as communication, scientific, engineering and materials science experiments.
The platform can hold up to 10 experiment payloads at a time and measures 5.6m (18.4ft) wide, 5m (16.4ft) high and 4m (13.1ft) long.
The radiators are part of the Active Thermal Control System (ATCS) which takes the heat out of the space station.
The cooling system in the radiators works like a car radiator except that it uses 99.9% pure ammonia instead of water, which would freeze in pipes outside the space station.
The ammonia collects heat from the space station's electronic equipment and module cooling components and transfers it to the large wing-like radiator panels to be dissipated into space as infrared radiation.
The radiator panels, each about 1.8m by 3.6m (6ft by 12 ft) in size, are designed to deploy from a stowed position about 0.6m (2ft) high to an extended position about 15m (49ft) in length. They are folded like an accordion to fit into the shuttle payload bay for transfer to the space station.
The radiators are shaded from sunlight and aligned towards the cold void of deep space.
The Cupola is the ultimate observation platform.
The Cupola will give astronauts fantastic views of Earth
The Italian-built segment will have six windows around the sides and one on top. These are not just for star-gazing. Nasa says the Cupola will give the crew an improved view of critical activities outside the station - including spacewalks, docking operations and exterior equipment.
The Cupola will be used specifically to monitor the approach and berthing of supply craft and other visiting vehicles.
It will also be the main location for controlling the robotic arm, Canadarm2.
The Cupola is scheduled to launch on station assembly mission 14A in early 2009. It will be added on to the forward port of Node 3, a connecting module to be installed in 2008.
Node 2 was named Harmony after a schools competition in the US
Harmony - or Node 2 - has been dubbed the gateway to the international partners involved in the Space Station.
Built in Italy for the United States, Harmony is a hi-tech hallway that will connect the existing US Destiny Laboratory to the European Columbus Laboratory and the Kibo Japanese Experiment Module, both to be installed later.
It will also provide connecting ports for Multi-Purpose Logistics Modules, the Japanese H II Transfer Vehicle and the Pressurized Mating Adapter 2 used for docking space shuttles. The space station robotic arm, Canadarm2, can operate from a powered grapple fixture on the outside of Harmony.
The node is similar to the six-sided Unity module that links the US and Russian sections of the station.
It is 7.2m (23.6ft) long and 4.4m (14.5ft) in diameter and increases the living and working space inside the station to approximately 500 cubic metres (18,000 cu ft).
The name Harmony was chosen after a competition among school children in the US.
In the future, permanent crew quarters will be added to Harmony, enabling the size of the ISS crew to increase to six. Crew quarters are rack-sized containers which will contain lighting, laptop connectiions, power, fans, and ventilation.
The Columbus laboratory is the European Space Agency's largest single contribution to the space station. The laboratory module, which can hold about 10 racks of experiments, will expand the research facilities of the space station.
Communication links to controllers and researchers on Earth will enable scientists to participate in their own experiments in space from several user centres.
Experiments are expected to relate to life sciences, materials sciences, fluid physics and other research in a weightless environment.
The control centre is based in Oberpfaffenhofen, Germany, where ground controllers will be able to communicate with the module as well as with researchers across Europe and their partners in the United States and Russia.
It is scheduled to be carried to the station on board Shuttle Atlantis in December 2007.
PLANNED ISS CONFIGURATION
The International Space Station is seen as key to future space exploration, aiding missions travelling to the Moon, Mars and beyond. On completion, it will be about four times larger than the old Russian space station Mir and will measure 110m (361 ft) end to end.