1. Contents
1 Purpose
o 1.1 Scientific research
o 1.2 Exploration
o 1.3 Education and cultural outreach
2 Origins
o 2.1 Mir-2
o 2.2 Freedom with Kibō
o 2.3 Columbus
3 Station structure
o 3.1 Assembly
o 3.2 Pressurised modules
o 3.3 Unpressurized elements
4 Station systems
o 4.1 Life support
o 4.2 Power and thermal control
o 4.3 Communications and computers
5 Station operations
o 5.1 Expeditions and private flights
o 5.2 Crew activities
o 5.3 Orbit and mission control
o 5.4 Repairs
6 Fleet operations
o 6.1 Currently docked/berthed
o 6.2 Scheduled launches and dockings/berthings
o 6.3 Docking
o 6.4 Launch and docking windows
7 Sightings
o 7.1 Naked eye
o 7.2 Astrophotography
8 Crew health and safety
o 8.1 Radiation
o 8.2 Stress

2. o 8.3 Medical
o 8.4 Orbital debris
9 Politics
o 9.1 International co-operation
o 9.2 China
o 9.3 End of mission
o 9.4 Program cost in United States dollars
10 Notes
11 References
12 External links
o 12.1 Children's websites
o 12.2 Live viewing
o 12.3 Contact the crew
o 12.4 Video
o 12.5 Image galleries
o 12.6 Research
o 12.7 Travel agency website

3. International Space Station
The International Space Station, as seen from Space ShuttleEndeavour in
May 2011.
ISS insignia
Station statistics
COSPAR ID 1998-067A
Call sign Alpha
Fully crewed 6
Crew Currently onboard 6
(Expedition 34)
Launch 1998–2020
Baikonur LC-81/23, LC-1/5
Launch pad
KSC LC-39,
Mass approximately 450,000 kg (990,000 lb)
Length 72.8 m
Width 108.5 m
c. 20 m (c. 66 ft)
Height nadir–zenith, arrays forward–aft
(27 November 2009)[dated info]
837 m3 (29,600 cu ft)
Pressurised volume
(21 March 2011)
Atmospheric pressure 101.3 kPa (29.91 inHg, 1 atm)

4. 402 km (250 mi) AMSL[1]
Perigee
(02 November 2012 04:38:51 epoch)
424 km (263 mi) AMSL[1]
Apogee
(02 November 2012 04:38:51 epoch)
Orbital inclination 51.6 degrees
7,706.6 m/s
Average speed
(27,743.8 km/h, 17,239.2 mph)
92 minutes 50 seconds[1]
Orbital period
(02 November 2012 04:38:51 epoch)
5140
Days in orbit
(16 December)
4427
Days occupied
(16 December)
80680
Number of orbits
(16 December)
Orbital decay 2 km/month
Statistics as of 9 March 2011
(unless noted otherwise)
References: [2][3][4][5][6][7]
Configuration
Station elements as of December 2011, but missing Pirs
(exploded view)
The International Space Station (ISS) is a habitable artificial satellite in low Earth orbit. It follows
the Salyut, Almaz, Skylab and Mir stations as the ninth space station to be inhabited. The ISS is a
modular structure whose first component was launched in 1998. Like many artificial satellites, the station

5. [8][9]
can be seen with the naked eye from Earth without any special equipment. The ISS consists of
pressurised modules, external trusses, solar arrays and other components. ISS components have been
[10]
launched by American Space Shuttles as well as Russian Proton and Soyuz rockets. Budget
constraints led to the merger of three space station projects with the Japanese Kibō module
and Canadian robotics. In 1993 the partially built Soviet/Russian Mir-2, the proposed American Freedom,
[10]
and the proposed European Columbus merged into a single multinational programme. The Russian
Federal Space Agency (RSA/RKA) is using the ISS as a work site to assemble their next space station,
called OPSEK. Modules and components for the new station began arriving on orbit in 2010, and the
RSA plans to commission the new station before the remainder of the ISS is de-orbited.
The ISS serves as a microgravity and space environment research laboratory in which crew members
conduct experiments in biology, human biology, physics, astronomy, meteorology and other
[11][12][13]
fields. The station is suited for the testing of spacecraft systems and equipment required for
[14]
missions to the Moon and Mars.
The station has been continuously occupied for 12 years and 44 days, having exceeded the previous
record of almost 10 years (or 3,634 days) held by Mir, in 2010. The station is serviced by
[15]
Soyuz spacecraft, Progress spacecraft, the Automated Transfer Vehicle, the H-II Transfer Vehicle, and
formerly the Space Shuttle. It has been visited by astronauts and cosmonauts from 15 different
[16]
nations. On 25 May 2012, Space Exploration Technologies Corporation (or SpaceX) became the
world's first privately held company to send a cargo load, via the Dragon spacecraft, to the International
[17]
Space Station.
The ISS programme is a joint project between five participating space agencies: NASA, the Russian
[15][18]
Federal Space Agency, JAXA, ESA, and CSA. The ownership and use of the space station is
[19]
established by intergovernmental treaties and agreements. The station is divided into two sections,
the Russian orbital segment (ROS) and the United States orbital segment (USOS), which is shared by
many nations. The ISS is maintained at an orbital altitude of between 330 km (205 mi) and 410 km
[20]
(255 mi). It completes 15.7 orbits per day. The ISS is funded until 2020, and may operate until
[21][22][23]
2028.

6. Purpose
According to the original Memorandum of Understanding between NASA and RSA, the International
Space Station was intended to be a laboratory, observatory and factory in space. It was also planned to
provide transportation, maintenance, and act as a staging base for possible future missions to the Moon,
[24]
Mars and asteroids. In the 2010 United States National Space Policy, the ISS was given additional
[25] [26]
roles of serving commercial, diplomatic and educational purposes.
[edit]Scientific research
Main article: Scientific research on the ISS
The ISS provides a platform to conduct scientific research that cannot be performed in any other way.
While small unmanned spacecraft can provide platforms for zero gravity and exposure to space, space
stations offer a long term environment where studies can be performed potentially for decades, combined
with ready access by human researchers over periods that exceed the capabilities of manned
[16][27]
spacecraft.
The Station simplifies individual experiments by eliminating the need for separate rocket launches and
research staff. The primary fields of research include Astrobiology, astronomy, human
research including space medicine and life sciences, physical sciences, materials science, Space
[11][12][13][28][29]
weather and weather on Earth (meteorology). Scientists on Earth have access to the crew's
data and can modify experiments or launch new ones, benefits generally unavailable on unmanned
[27]
spacecraft. Crews fly expeditions of several months duration, providing approximately 160 man-hours a
[11][30]
week of labour with a crew of 6.
Kibō is intended to accelerate Japan's progress in science and technology, gain new knowledge and
[31]
apply it to such fields as industry and medicine.
In order to detect dark matter and answer other fundamental questions about our universe, engineers and
scientists from all over the world built the Alpha Magnetic Spectrometer (AMS), which NASA compares to
the Hubble telescope, and says could not be accommodated on a free flying satellite platform due in part
[32][33]
to its power requirements and data bandwidth needs.

7. The space environment is hostile to life. Unprotected presence in space is characterised by an intense
radiation field (consisting primarily of protons and other subatomic charged particles from the solar wind,
[34]
in addition to cosmic rays), high vacuum, extreme temperatures, and microgravity. Some simple forms
[35] [36]
of life called extremophiles, including small invertebrates called tardigrades can survive in this
environment in an extremely dry state called desiccation.
Medical research improves knowledge about the effects of long-term space exposure on the human body,
including muscle atrophy, bone loss, and fluid shift. This data will be used to determine whether
lengthy human spaceflight and space colonisation are feasible. As of 2006, data on bone loss and
muscular atrophy suggest that there would be a significant risk of fractures and movement problems if
astronauts landed on a planet after a lengthy interplanetary cruise, such as the six-month interval
[37][38]
required to travel to Mars. Medical studies are conducted aboard the ISS on behalf of the National
Space Biomedical Research Institute (NSBRI). Prominent among these is the Advanced Diagnostic
Ultrasound in Microgravity study in which astronauts perform ultrasound scans under the guidance of
remote experts. The study considers the diagnosis and treatment of medical conditions in space. Usually,
there is no physician on board the ISS and diagnosis of medical conditions is a challenge. It is anticipated
that remotely guided ultrasound scans will have application on Earth in emergency and rural care
[39][40][41]
situations where access to a trained physician is difficult.
[edit]Microgravity
A comparison between the combustion of a candle on Earth (left) and in a microgravity environment, such as that found on
the ISS (right)
Contrary to popular belief, the earth's gravity is only slightly less at the altitude of the ISS as at the
surface. According to the equivalence principle, gravity only seems absent because, like any orbiting
object, it is in continuous freefall. This state of perceived weightlessness is not perfect however, being
[42]
disturbed by five separate effects:
Drag from the residual atmosphere; when the ISS enters the Earth's shadow, the main solar panels
are rotated to minimise this aerodynamic drag, helping reduce orbital decay.

8. Vibration from movements of mechanical systems and the crew.
Actuation of the on-board altitude control moment gyroscopes.
Thruster firings for altitude or orbital changes.
Gravity-gradient effects, also known as tidal effects. Items not at the exact ISS center of mass would,
if not attached to the station, follow slightly different orbits than that of the ISS as a whole. Those
closer to the earth would tend to follow faster, shorter orbits and move forward along the velocity
vector. Those farther away would have slower, longer orbits and move rearward against the velocity
vector. Those to the left or right of the ISS center of mass would be in different orbital planes. Being
attached to the rigid ISS, however, these items experience small forces that keep them moving along
with the ISS center of mass.
Researchers are investigating the effect of the station's near-weightless environment on the evolution,
development, growth and internal processes of plants and animals. In response to some of this data,
NASA wants to investigate microgravity's effects on the growth of three-dimensional, human-like tissues,
[12]
and the unusual protein crystals that can be formed in space.
The investigation of the physics of fluids in microgravity will allow researchers to model the behaviour of
fluids better. Because fluids can be almost completely combined in microgravity, physicists investigate
fluids that do not mix well on Earth. In addition, an examination of reactions that are slowed by low gravity
[12]
and temperatures will give scientists a deeper understanding ofsuperconductivity.
The study of materials science is an important ISS research activity, with the objective of reaping
[43]
economic benefits through the improvement of techniques used on the ground. Other areas of interest
include the effect of the low gravity environment on combustion, through the study of the efficiency of
burning and control of emissions and pollutants. These findings may improve current knowledge about
energy production, and lead to economic and environmental benefits. Future plans are for the
researchers aboard the ISS to examine aerosols, ozone, water vapour, and oxidesin Earth's atmosphere,
[12]
as well as cosmic rays, cosmic dust, antimatter, and dark matter in the universe.
[edit]Exploration
A 3D plan of the MARS-500 complex, used for ground-based experiments which complement ISS-based preparations for
amanned mission to Mars
The ISS provides a location in the relative safety of Low Earth Orbit to test spacecraft systems that will be
required for long-duration missions to the Moon and Mars. This provides experience in operations,
maintenance as well as repair and replacement activities on-orbit, which will be essential skills in

9. operating spacecraft farther from Earth, mission risks can be reduced and the capabilities of
[14]
interplanetary spacecraft advanced. Referring to theMARS-500 experiment, ESA states that "Whereas
the ISS is essential for answering questions concerning the possible impact of weightlessness, radiation
and other space-specific factors, aspects such as the effect of long-term isolation and confinement can be
[44]
more appropriately addressed via ground-based simulations". Sergey Krasnov, the head of human
space flight programmes for Russia's space agency, Roscosmos, in 2011 suggested a "shorter version"
[45]
of MARS-500 may be carried out on the ISS.
In 2009, noting the value of the partnership framework itself, Sergey Krasnov wrote, "When compared
with partners acting separately, partners developing complementary abilities and resources could give us
much more assurance of the success and safety of space exploration. The ISS is helping further advance
near-Earth space exploration and realisation of prospective programmes of research and exploration of
[46]
the Solar system, including the Moon and Mars." A manned mission to Mars, however, may be a
multinational effort involving space agencies and countries outside of the current ISS partnership. In 2010
ESA Director-General Jean-Jacques Dordain stated his agency was ready to propose to the other 4
[47]
partners that China, India and South Korea be invited to join the ISS partnership. NASA chief Charlie
[48]
Bolden stated in Feb 2011 "Any mission to Mars is likely to be a global effort". Currently, American
[49]
legislation prevents NASA co-operation with China on space projects.
[edit]Education and cultural outreach
The ISS crew provide opportunities for students on Earth by running student-developed experiments,
making educational demonstrations, allowing for student participation in classroom versions of ISS
[15][50]
experiments, and directly engaging students using radio, videolink and email. ESA offers a wide
[51]
range of free teaching materials that can be downloaded for use in classrooms. In one lesson, students
can navigate a 3-D model of the interior and exterior of the ISS, and face spontaneous challenges to
[52]
solve in real time.
JAXA aims both to "Stimulate the curiosity of children, cultivating their spirits, and encouraging their
passion to pursue craftsmanship", and to "Heighten the child's awareness of the importance of life and
[53]
their responsibilities in society." Through a series of education guides, a deeper understanding of the
[54][55]
past and near-term future of manned space flight, as well as that of Earth and life, will be learned. In
the JAXA Seeds in Space experiments, the mutation effects of spaceflight on plant seeds aboard the ISS
is explored. Students grow sunflower seeds which flew on the ISS for about nine months as a start to
‗touch the Universe‘. In the first phase of Kibō utilisation from 2008 to mid-2010, researchers from more
[56]
than a dozen Japanese universities conducted experiments in diverse fields.
Susan J. Helms, Expedition Two flight engineer, A student speaks to crew

10. talks to amateur radio operators on Earth from using Amateur Radio,
the Amateur radio workstation in the Zarya. provided free by ARISS.
Cultural activities are another major objective. Tetsuo Tanaka, director of JAXA's Space Environment and
Utilization Center, says "There is something about space that touches even people who are not interested
[31]
in science."
Amateur Radio on the ISS (ARISS) is a volunteer programme which encourages students worldwide to
pursue careers in science, technology, engineering and mathematics through amateur
radio communications opportunities with the ISS crew. ARISS is an international working group,
consisting of delegations from 9 countries including several countries in Europe as well as Japan, Russia,
Canada, and the United States. In areas where radio equipment cannot be used, speakerphones connect
[57]
students to ground stations which then connect the calls to the station.
First Orbit is a feature-length documentary film about Vostok 1, the first manned space flight around the
Earth. By matching the orbit of the International Space Station to that of Vostok 1 as closely as possible,
in terms of ground path and time of day, documentary filmmaker Christopher Riley and ESA
astronaut Paolo Nespoli were able to film the view that Yuri Gagarin saw on his pioneering orbital space
flight. This new footage was cut together with the original Vostok 1 mission audio recordings sourced from
the Russian State Archive. Nespoli, during Expedition 26/27, filmed the majority of the footage for this
[58]
documentary film, and as a result is credited as its director of photography. The film was streamed
[59]
through the website www.firstorbit.org in a global YouTube premiere in 2011, under a free license.
[edit]Origins
The International Space Station programme represents a combination of three national space station
projects: the Russian/Soviet Mir-2, NASA's Freedom including the Japanese Kibō laboratory, and the
European Columbus space stations. Canadian robotics supplement these projects.
Mir-2 was originally authorised in the February 1976 resolution setting forth plans for development of third
generation Soviet space systems; the first module, which would have served the same function as Zarya,
was destroyed in a launch mishap.
In the early 1980s, NASA planned to launch a modular space station called Freedom as a counterpart to
the Soviet Salyut and Mir space stations. Freedom was never constructed and the remnants of the project
became part of the ISS. The Japanese Experiment Module (JEM), or Kibō, was announced in 1985, as
part of the Freedom space station in response to a NASA request in 1982.
In Rome in early 1985, science ministers from the European Space Agency (ESA) countries approved
the Columbus program, the most ambitious effort in space undertaken by that organisation at the time.
The plan spearheaded by Germany and Italy included a module which would be attached to Freedom,
and with the capability to evolve into a full-fledged European orbital outpost before the end of the century.
The space station was also going to tie the emerging European and Japanese national space
programmes closer to the U.S.-led project, thereby preventing those nations from becoming major,
[60]
independent competitors too.
In September 1993, American Vice-President Al Gore and Russian Prime Minister Viktor
Chernomyrdin announced plans for a new space station, which eventually became the International

11. [61]
Space Station. They also agreed, in preparation for this new project, that the United States would be
[62]
involved in the Mir programme, including American Shuttles docking, in the Shuttle-Mir Program.
[edit]Mir-2
Main articles: Mir, Mir-2, Polyus (spacecraft), Buran program, and Energia
The Soviet Buran shuttle would have carried modules up to 30 tons to MIR-2. 80–100 ton modules could have used its
launcher without the shuttle (seen here withAn-225, the heaviest aeroplane).
The Russian Orbital Segment (ROS or RS) is the eleventh Soviet-Russian space station. Mir ("Peace")
and the ISS are successors to the Salyut("Fireworks") and Almaz ("Diamond") stations. The first MIR-2
module was launched in 1986 by an Energia heavy-lift expendable launch system. The launcher worked
properly, however the Polyus payload fired its engines to insert itself into orbit whilst in the wrong position
due to a programming error, and re-entered the atmosphere. The planned station changed several times,
but Zvezda was always the service module, containing the station's critical systems such as life support.
The station would have used the Buran spaceplane and Proton rockets to lift new modules into orbit. The
spaceframe of Zvezda, also called DOS-8 serial number 128, was completed in February 1985 and major
[63]
internal equipment was installed by October 1986.
The Polyus module or spacecraft would have served as the FGB, a foundation which provides propulsion
and guidance, but it lacks life support. Polyus was a satellite interceptor/destroyer, carrying a 1 megawatt
carbon dioxide laser. The module had a length of almost 37 m and a diameter of 4.1 m, weighed nearly
80 t, and included 2 principal sections, the smallest, the functional service block (FGB), and the largest,
[64]
the aim module.
In 1983, the design was changed and the station would consist of Zvezda, followed by several 90 metric
ton modules and a truss structure similar to the current station. The draft was approved by NPO Energia
Chief Semenov on 14 December 1987 and announced to the press as 'Mir-2' in January 1988. This
station would be visited by the Soviet Buran, but mainly resupplied by Progress-M2 spacecraft. Orbital
[63]
assembly of the station was expected to begin in 1993. In 1993 with the collapse of the Soviet Union, a
redesigned smaller Mir-2 was to be built whilst attached to Mir, just as OPSEK is being assembled whilst
attached to the ISS.
[edit]Freedom with Kibō
Main articles: Space Station Freedom, Kibō, and H-II Transfer Vehicle

12. Artist's conception of the proposed "Power Tower" space station with the Japanese Experiment Module attached
Approved by then-president Ronald Reagan and announced in the 1984 State of the Union Address, "We
can follow our dreams to distant stars, living and working in space for peaceful economic and scientific
gain", the proposed Freedom changed considerably.
NASA's first cost assessment in 1987 revealed the "Dual Keel" Station would cost $14.5 billion. This
caused a political uproar in Congress, and NASA and Reagan Administration officials reached a
compromise in March 1987 which allowed the agency to proceed with a cheaper $12.2-billion Phase One
Station that could be completed after 10 or 11 Shuttle assembly flights. This design initially omitted the
$3.4-billion 'Dual Keel' structure and half of the power generators. The new Space Station configuration
was named Freedom by Reagan in June 1988. Originally, Freedom would have carried two 37.5 kW solar
arrays. However, Congress quickly insisted on adding two more arrays for scientific users. The Space
Station programme was plagued by conflicts during the entire 1984–87 definition phase. In 1987, the
Department of Defense (DoD) briefly demanded to have full access to the Station for military research,
despite strong objections from NASA and the international partners. Besides the expected furore from the
international partners, the DoD position sparked a shouting match between Defense Secretary Caspar
Weinberger and powerful members of Congress that extended right up to the final Fiscal 1988 budget
[65]
authorisation in July 1987. Reagan wanted to invite other NATO countries to participate in the U.S-led
project, since the Soviet Union had been launching international crews to their Salyut space stations
since 1971. At one point, then-anonymous disgruntled NASA employees calling themselves "Center for
Strategic Space Studies" suggested that instead of building Freedom, NASA should take the back-up
[66]
Skylab from display in the National Air and Space Museum in Washington and launch that.
An agreement signed in September 1988 allocated 97% of the US lab resources to NASA while the
Canadian CSA would receive 3% in return for its contribution to the programme. Europe and Japan would
retain 51% of their own laboratory modules. Six Americans and two international astronauts would be
permanently based on Space Station Freedom. Several NASA Space Shuttle missions in the 1980s and
early 1990s included spacewalks to demonstrate and test space station construction techniques.

13. The Japanese Experiment Module (JEM), christened Kibō ("hope") in 1999, is Japan's first manned
spacecraft. Kibō consists of a pressurised laboratory dedicated to advanced technology experiments,
education and art, a cargo bay, an unpressurised pallet for vacuum experiments in space, a robotic arm,
and interorbital communication system. While the proposed space station was redesigned many times
around Kibō, the only significant change has been the placement of its ballistic shielding. Its final position
at the front of the station increases the risk of damage from debris. The ESA and NASA, by contrast, both
reduced the size of their laboratories over the course of the program. The Japanese National Space
Development Agency (NASDA) formally submitted the JEM proposal to NASA in March 1986, and by
[60][67][68]
1990 design work began. Constructed in the Tobishima Plant of Nagoya Aerospace Systems
Works, by Mitsubishi Heavy Industries, Ltd., Kibō made its way to the Tsukuba Space Center and in 2003
Kibō was shipped, first by river barge and then by ship, to America. In 2010, Kibō won the Good Design
Award, a 55 year old consumer and industry award which identifies the best of Japanese
[69][70]
craftsmanship.
A decade before Zarya was launched into orbit, Japan was working on the development of its own space
shuttle, intended to use the H-II launcher. Depending on the configuration of the launcher, it would weigh
between 10 and 20 metric tons and mix crew and cargo together. It would take off vertically on its booster
and at the end of its mission re-enter and land just as the NASA and Soviet shuttles did. The program
[71][72]
was terminated by JAXA in 2003 after scale mockup testing.

14. Columbus
Main articles: Columbus ISS module, Man-Tended Free Flyer, and Hermes spaceplane
The first elements of the Columbus program were expected to fly as early as 1992, to coincide with the
500th anniversary of Columbus' voyage to America. ESA and NASA clashed over the very concept of the
Columbus program in 1986. America objected to ESA's using Columbus as building block of a future
European space station, and were concerned that they would facilitate the creation of a potential
competitor if the manned space outpost fulfilled its promise as supplier of commercially viable products,
such as new materials and pharmaceuticals. Plans were scaled down as a result, and by 1988, Europe
proposed to participate with three elements, the Columbus module, the Man-Tended Free Flyer (MTFF),
[73] [74]
and the Polar Platform (PPF), supported by theAriane-5 launcher and the Hermes spaceplane.
The Columbus Man-Tended Free Flyer (MTFF) was an ESA programme to develop a space station that
could be used for a variety of microgravity experiments while serving ESA's needs for an autonomous
[75]
manned space platform. The MTFF would be a space station without long term life support, visited by
short term crews to replenish and maintain experiments in a Zero-G environment free of vibrations
caused by a permanent crew. The project was canceled after budget constraints caused by German
reunification. The Hermes spaceplane is comparable in function to the American and Soviet space
shuttles, with a smaller crew of up to 6 (reduced to 3 with ejection seats after the Columbia disaster) and
substantially smaller cargo capacity, 4,550 kg, comparable to ISS unmanned cargo ships.
By 1991 the Columbus and Hermes pre-development activities were good enough to progress into full
development, however profound geopolitical changes prompted examining broader international
cooperation, in particular with the Russian Federation. ESA Member States approved the complete
development of the Attached Pressurised Module (APM) and the Polar Platform (PPF) for Columbus, but
the Man-Tended Free-Flyer (MTFF) was abandoned. The Hermes programme was reoriented into the
Manned Space Transportation Programme (MSTP), and a three-year period extending from 1993 to 1995
was agreed on in order to define a future manned space transportation system in cooperation with
[76][77]
Russia, including joint development and use of Mir-2.
The ESA ATV robot spacecraft is a powerful 'space tug' that can be adapted to shuttle supplies into Mars
[78]
orbit. Its propulsion is arranged with a central hollow section, to allow the possibility of a docking port at
both ends. It could then form larger assemblies, strung together as a space station or allowing piggyback
[citation needed]
docking to Zvezda.
[edit]Station structure

15. Expedition 18 commander Michael Fincke's Station layout, photographed from Soyuz TMA-20,
video tour of the habitable part of the ISS with NASA's Endeavour docked
from January 2009
The ISS follows Salyut and Almaz series, Cosmos 557, Skylab, and Mir as the 11th space station
launched, as the Genesis prototypes were never intended to be manned. The ISS is a third
[79] [80]
generation modular space station.
Other examples of modular station projects include the Soviet/Russian Mir, Russian OPSEK,
and Chinese space station. The first space station, Salyut 1, and other one-piece or 'monolithic' first
generation space stations, such as Salyut 2,3,4,5, DOS 2, Kosmos 557, Almaz and
[81]
NASA's Skylab stations were not designed for re-supply. Generally, each crew had to depart the station
to free the only docking port for the next crew to arrive, Skylab had more than one docking port but was
not designed for resupply. Salyut 6 and 7 had more than one docking port and were designed to be
[82]
resupplied routinely during crewed operation. Modular stations can allow the mission to be changed
over time and new modules can be added or removed from the existing structure, allowing greater
flexibility.
Below is a diagram of major station components. The blue areas are pressurised sections accessible by
the crew without using spacesuits. The station's unpressurised superstructure is indicated in red. Other
unpressurised components are yellow. Note that the Unity node joins directly to the Destiny laboratory.
For clarity, they are shown apart.
Russian
docking port
Solar Zvezda DOS-8 Solar
array Service Module array
Russian Poisk(MRM-2) Pirs Russian
docking port Airlock Airlock docking port

16. Nauka lab to European
Replace Pirs Robotic Arm
Solar Zarya FGB Solar
array (first module) array
Leonardo Rassvet Russian
cargo bay (MRM-1) docking port
PMA 1
Quest Unity Tranquility PMA 3
Airlock Node 1 Node 3 docking port
ESP-2 Cupola
Solar Heat Heat
Solar array Solar array Solar array
array Radiator Radiator
ELC 2, AMS Z1 truss ELC 3
S5/6 Truss S3/S4 Truss S1 Truss S0 Truss P1 Truss P3/P4 Truss P5/6 Truss
ELC 4, ESP
ELC 1
3
Dextre Canadarm2
Solar
Solar array Solar array Solar array
array
External Destiny
stowage Laboratory
Kibō logistics
Cargo Bay
HTV/Dragon berth HTV/Dragon berth
(docking port) (docking port)

17. Robotic Arm
External Columbus Harmony Kibō Kibō
Payloads Laboratory (Node 2) Laboratory External Platform
PMA 2
docking port
[edit]Assembly
Main article: Assembly of the International Space Station
See also: List of ISS spacewalks
Ron Garan during STS-124 uses a computer controlled screwdriver for speed, torque and number of turns.
The assembly of the International Space Station, a major endeavour in space architecture, began in
[3]
November 1998. Russian modules launched and docked robotically, with the exception of Rassvet. All
other modules were delivered by the Space Shuttle, which required installation by ISS and shuttle
crewmembers using the SSRMS and EVAs; as of 5 June 2011, they had added 159 components during
more than 1,000 hours of EVA activity. 127 of these spacewalks originated from the station, while the
[2]
remaining 32 were launched from the airlocks of docked Space Shuttles. The beta angle of the station
had to be considered at all times during construction, as the station's beta angle is directly related to the
percentage of its orbit that the station (as well as any docked or docking spacecraft) is exposed to the
[83]
sun; the Space Shuttle would not perform optimally above a limit called the "beta cutoff". Rassvet was
delivered by NASA's Atlantis Space Shuttle in 2010 in exchange for the Russian Proton delivery of the
[84]
United States-funded Russian-built Zarya Module in 1998. Robot arms rather than EVAs were utilised
in its installation (docking).
The first segment of the ISS, Zarya, was launched on 20 November 1998 on an autonomous
Russian Proton rocket. It provided propulsion, orientation control, communications, electrical power, but
lacked long-term life support functions. Two weeks later a passive NASA module Unity was launched
aboard Space Shuttle flight STS-88 and attached to Zarya by astronauts during EVAs. This module has
two Pressurized Mating Adapters (PMAs), one connects permanently to Zarya, the other allows the
Space Shuttle to dock to the space station. At this time, the Russian station Mir was still inhabited. The

18. ISS remained unmanned for two years, during which time Mir was de-orbited. On 12 July
2000 Zvezda was launched into orbit. Preprogrammed commands on board deployed its solar arrays and
communications antenna. It then became the passive vehicle for a rendezvous with the Zarya and Unity.
As a passive "target" vehicle, the Zvezda maintained a stationkeeping orbit as the Zarya-Unity vehicle
performed the rendezvous and docking via ground control and the Russian automated rendezvous and
docking system. Zarya's computer transferred control of the station to Zvezda's computer soon after
docking. Zvezda added sleeping quarters, a toilet, kitchen, CO2 scrubbers, dehumidifier, oxygen
generators, exercise equipment, plus data, voice and television communications with mission control.
[85][86]
This enabled permanent habitation of the station.
The first resident crew, Expedition 1, arrived in November 2000 on Soyuz TM-31, midway between the
flights of STS-92 and STS-97. These two Space Shuttle flights each added segments of the
station's Integrated Truss Structure, which provided the station with Ku-band communication for U.S.
television, additional attitude support needed for the additional weight of the USOS, and substantial solar
[87]
arrays supplementing the station's existing 4 solar arrays.
Partially constructed ISS in December 2002
Over the next two years the station continued to expand. A Soyuz-U rocket delivered the Pirs docking
compartment. The Space Shuttles Discovery,Atlantis, and Endeavour delivered
the Destiny laboratory and Quest airlock, in addition to the station's main robot arm, the Canadarm2, and
several more segments of the Integrated Truss Structure.
The expansion schedule was interrupted by the destruction of the Space Shuttle Columbia on STS-107 in
2003, with the resulting hiatus in the Space Shuttle programme halting station assembly until the launch
[88]
of Discovery on STS-114 in 2005.
The official resumption of assembly was marked by the arrival of Atlantis, flying STS-115, which delivered
the station's second set of solar arrays. Several more truss segments and a third set of arrays were
delivered on STS-116, STS-117, and STS-118. As a result of the major expansion of the station's power-
generating capabilities, more pressurised modules could be accommodated, and the Harmony node
and Columbus European laboratory were added. These were followed shortly after by the first two
components of Kibō. In March 2009, STS-119 completed the Integrated Truss Structure with the
installation of the fourth and final set of solar arrays. The final section of Kibō was delivered in July 2009
on STS-127, followed by the Russian Poisk module. The third node, Tranquility, was delivered in
February 2010 during STS-130 by the Space Shuttle Endeavour, alongside the Cupola, closely followed
in May 2010 by the penultimate Russian module, Rassvet, delivered by Space Shuttle Atlantis on STS-
132. The last pressurised module of the USOS, Leonardo, was brought to the station by Discovery on her

19. final flight, STS-133, followed by the Alpha Magnetic Spectrometer on STS-134, delivered
[citation needed]
by Endeavour.
ISS in orbit docked with the Space Shuttle Endeavour in May 2011
As of June 2011, the station consisted of fifteen pressurised modules and the Integrated Truss Structure.
Still to be launched are the RussianMultipurpose Laboratory Module Nauka and a number of external
components, including the European Robotic Arm. Assembly is expected to be completed by 2012, by
[3][89]
which point the station will have a mass in excess of 400 metric tons (440 short tons).
The gross mass of the station is not possible to calculate with precision. The total launch weight of the
[90]
modules on orbit is 417,289 kg (919,960 lb) (as of 03/09/2011). The mass of experiments, spare parts,
personal effects, crew, foodstuff, clothing, propellants, water supplies, gas supplies, docked spacecraft,
and other items add to the total mass of the station. Gas (Hydrogen) is constantly vented overboard by
the Oxygen generators.
[edit]Pressurised modules
Main article: Assembly sequence
Unity node (top) and Zarya From top to bottom: Unity, Zarya,
(with solar panels deployed) Zvezda modules with Progress M1-
in 1998 3 docked
Zarya (Russian: ; lit. dawn), also known as the Functional Cargo Block or FGB(Russian: ФГБ),
was the first module of the station, launched on 20 November 1998 on a Russian Proton rocket from Site

20. 81 in the first and largest spaceport, Baikonur to a 400 km (250 mi) high orbit. After parking in orbit, the
Zarya Module provided orientation control, communications and electrical power for itself, and for the
passive Node 1 (Unity) attached later, while the station awaited launch of the third component, a Russian-
provided crew living quarters and early station core, the service module Zvezda. The Service Module
enhanced or replaced many functions of Zarya. The FGB is a descendant of the TKS spacecraft designed
for the Russian Salyut programme. 6,100 kg of propellant fuel can be stored and transferred automatically
to and from ships docked to the Russian portion of the station – the Russian Orbital Segment (ROS).
Zarya was originally intended as a module for the Russian Mir space station, but was not flown as of the
end of the Mir-1 programme. Development costs for Zarya were paid for by Russia (and the former Soviet
Union), spread across previous space station programmes, and some construction and preparation costs
were paid for by the United States.
Unity, a passive connecting module was the first U.S.-built component of the Station. It is cylindrical in
shape, with six berthing locations facilitating connections to other modules. Unity was carried into orbit as
the primary cargo of STS-88 in 1998.
Zvezda (Russian: Звезда, meaning "star"), DOS-8, also known as the Service
Module or SM (Russian: СМ). It provides all of the station's critical systems, its addition rendered the
station permanently habitable for the first time, adding life support for up to six crew and living quarters for
[91]
two. Zvezda's DMS-R computer handles guidance, navigation & control for the entire space station. A
second computer which performs the same functions is installed in the Nauka FGB-2. The rocket used for
[92]
Zvezda's launch was one of the first to carry advertising. The space frame was completed in February
1985, major internal equipment was installed by October 1986, and it was launched on 12 July 2000.
Zvezda is at the rear of the station according to its normal direction of travel and orientation, its engines
are used to boost the station's orbit. Alternatively Russian and European spacecraft can dock to Zvezda's
aft (rear) port and use their engines to boost the station.
Destiny is the primary research facility for United States payloads aboard the ISS. In 2011, NASA
solicited proposals for a not-for-profit group to manage all American science on the station which does not
relate to manned exploration. The module houses 24 International Standard Payload Racks, some of
which are used for environmental systems and crew daily living equipment. Destinyalso serves as the
[93]
mounting point for the station's Truss Structure.
Blue EVA hatches in the Pirs airlock frame cosmonaut Thomas Reiter (left), is attired in a liquid cooling and
Maxim Suraev Flight engineer who displays two Orlanventilation garment that complements the EMU style
space suits space suit worn by Jeffrey N. Williams in the Quest

21. Airlock
Quest is the only USOS airlock, Quest hosts spacewalks with both United States EMU and
RussianOrlan spacesuits. Quest consists of two segments; the equipment lock, that stores spacesuits
and equipment, and the crew lock, from which astronauts can exit into space. This module has a
separately controlled atmosphere. Crew sleep in this module, breathing a low nitrogen mixture the night
before scheduled EVAs, to avoid decompression sickness (known as "the bends") in the low pressure
[94]
suits.
Pirs (Russian: Пирс, meaning "pier"), (Russian: Стыковочный отсек), "docking module", SO-1 or DC-1
(docking compartment), and Poisk (Russian: ; lit. Search), also known as the Mini-Research
Module 2 (MRM 2), Малый исследовательский модуль 2, or МИМ 2. Pirs and Poisk are Russian
airlock modules. Each of these modules have 2 identical hatches. An outward opening hatch on the MIR
space station failed after it swung open too fast after unlatching, due to a small amount of air pressure
[95]
remaining in the airlock. A different entry was used, and the hatch repaired. All EVA hatches on the ISS
open inwards and are pressure sealing. Pirs is used to store, service, and refurbish Russian Orlan suits
and provides contingency entry for crew using the slightly bulkier American suits. The outermost docking
ports on both airlocks allow docking of Soyuz and Progress spacecraft, and the automatic transfer of
[96]
propellants to and from storage on the ROS.
Harmony, is the second of the station's node modules and the utility hub of the USOS. The module
contains four racks that provide electrical power, bus electronic data, and acts as a central connecting
point for several other components via its six Common Berthing Mechanisms (CBMs). The European
Columbus and Japanese Kibō laboratories are permanently berthed to two of the radial ports, the other
two can used for the HTV. American Shuttle Orbiters docked with the ISS via PMA-2, attached to the
forward port. Tranquility is the third and last of the station's U.S. nodes, it contains an additional life
support system to recycle waste water for crew use and supplements oxygen generation. Three of the
four berthing locations are not used. One location has the cupola installed, and one has the docking port
adapter installed.
Not large enough for crew using spacesuits, the airlock The Columbus Module in 2008
on Kibō has an internal sliding drawer for experiments.
Columbus, the primary research facility for European payloads aboard the ISS, provides a generic
laboratory as well as facilities specifically designed for biology, biomedical research and fluid physics.
Several mounting locations are affixed to the exterior of the module, which provide power and data to

22. external experiments such as the European Technology Exposure Facility (EuTEF), Solar Monitoring
Observatory, Materials International Space Station Experiment, and Atomic Clock Ensemble in Space. A
[97][98]
number of expansions are planned for the module to study quantum physics andcosmology. ESA‘s
development of technologies on all the main areas of life support has been ongoing for more than 20
years and are/have been used in modules such as Columbus and the ATV. The German Aerospace
Center DLR manages ground control operations for Columbus and the ATV is controlled from the French
CNES Toulouse Space Center.
Kibō (Japanese: きぼう, "hope") is the largest single ISS module. This laboratory is used to carry out
research in space medicine, biology, Earth observations, materials production, biotechnology,
communications research, and has facilities for growing plants and fish. During August 2011, an
observatory mounted on Kibō, which utilises the ISS's orbital motion to image the whole sky in the X-ray
[99][100]
spectrum, detected for the first time the moment a star was swallowed by a black hole. The
laboratory contains a total of 23 racks, including 10 experiment racks and has a dedicated airlock for
experiments. In a 'shirt sleeves' environment, crew attach an experiment to the sliding drawer within the
airlock, close the inner, and then open the outer hatch. By extending the drawer and removing the
experiment using the dedicated robotic arm, payloads are placed on the external platform. The process
can be reversed and repeated quickly, allowing access to maintain external experiments without the
delays caused by EVA's. Only the Russian and Japanese laboratories have this feature. A smaller
pressurised module is attached to the top of Kibō, serving as a cargo bay. The dedicated Interorbital
communications system allows large amounts of data to be beamed from Kibō's ICS, first to the
Japanese KODAMA satellite in geostationary orbit, then to Japanese ground stations. When a direct
communication link is used, contact time between the ISS and a ground station is limited to approximately
10 minutes per visible pass. When KODAMA relays data between a LEO spacecraft and a ground station,
real-time communications are possible in 60% of the flight path of the spacecraft. Ground staff use tele-
present robotics to conduct on-orbit research without crew intervention.
The Cupola's design has been compared toDmitri Kondratyev and Paolo Nespoli in the Cupola. Background left to
the Millennium Falcon from the motion right, Progress M-09M, Soyuz TMA-20, the Leonardomodule and HTV-
picture Star Wars. 2.

23. Tracy Caldwell Dyson poses for a photo in the Cupola, admiring the view of the Earth.
Cupola is a seven window observatory, used to view Earth and docking spacecraft. Its name derives from
the Italian word cupola, which means "dome". The Cupola project was started by NASA and Boeing, but
cancelled due to budget cuts. A barter agreement between NASA and the ESA resulted in the Cupola's
development being resumed in 1998 by the ESA. The module comes equipped with robotic workstations
for operating the station's main robotic arm and shutters to protect its windows from damage caused by
micrometeorites. It features 7 windows, with a 80-centimetre (31 in) round window, the largest window on
the station. The distinctive design has been compared to the 'turret' of the fictitious Millennium Falcon in
[101][102]
the motion picture Star Wars; the original prop lightsaber used by actor Mark Hamill as Luke
[103]
Skywalker in the 1977 film was flown to the station in 2007, and the Falcon rockets commercial ships
that come to the station use, are named after the Millennium Falcon itself.
Rassvet (Russian: ; lit. "dawn"), also known as the Mini-Research Module 1 (MRM-1)
(Russian: Малый исследовательский модуль, МИМ 1) and formerly known as the Docking Cargo
Module (DCM), is similar in design to the Mir Docking Module launched on STS-74 in 1995. Rassvet is
primarily used for cargo storage and as a docking port for visiting spacecraft. It was flown to the ISS
aboard NASA's Space Shuttle Atlantis on the STS-132 mission and connected in May
[104][105]
2010, Rassvet is the only Russian owned module launched by NASA, to repay for the launch of
[106]
Zarya, which is Russian designed and built, but partially paid for by NASA. Rassvet was launched with
the Russian Nauka Laboratory's Experiments airlock temporarily attached to it, and spare parts for the
European Robotic Arm.
Leonardo Permanent Multipurpose Module (PMM) The three NASA Space Shuttle MPLM cargo
containers Leonardo, Raffaello and Donatello, were built for NASA in Turin, Italy by Alcatel Alenia Space,
[107]
now Thales Alenia Space. The MPLMs are provided to the ISS programme by the Italy (independent
of Italy's role as a member state of ESA) to NASA and are considered to be U.S. elements. In a bartered
exchange for providing these containers, the U.S. has given Italy research time aboard the ISS out of the
[108]
U.S. allotment in addition to that which Italy receives as a member of ESA. The Permanent
Multipurpose Module was created by converting Leonardo into a module that could be permanently
[109][110][111]
attached to the station.
[edit]Scheduled additional modules
Nauka (Russian: ; lit. Science), also known as the Multipurpose Laboratory Module (MLM)
or FGB-2, (Russian: Многофункциональный лабораторный модуль, or МЛМ), is the major Russian
[112]
laboratory module. It is scheduled to arrive at the station in 2014 and will replace PIRS. Prior to the

24. arrival of the Nauka, a progress robot spacecraft will dock with PIRS, depart with that module, and both
will be discarded. It contains an additional set of life support systems and orientation control. Originally it
would have routed power from the single Science-and-Power Platform, but that single module design
changed over the first ten years of the ISS mission, and the two science modules which attach to Nauka
via the Node Module each incorporate their own large solar arrays to power Russian science experiments
in the ROS. Nauka's mission has changed over time. During the mid 1990s, it was intended as a backup
for the FGB, and later as a universal docking module (UDM); its docking ports will be able to support
automatic docking of both space craft, additional modules and fuel transfer. Nauka is a module in the 20
ton class and has its own engines. Smaller ISS modules (less than 10 tons) which dock to the ROS do
not have engines of their own, but rely for propulsion upon the spaceship that brings them to the station.
Zvezda and Zarya, like Nauka, weigh about 20 tons each and are launched by the larger Proton rockets
rather than by Soyuz rockets. They are the only 3 modules on the ISS that contain engines, or navigation
computers with star, sun and horizon sensors, to enable flight and station-keeping. Nauka will be
separated from the ISS before de-orbit, together with support modules, and become the OPSEK space
station.
Node Module (UM)/(NM) This 4-ton ball shaped module will support the docking of two scientific and
power modules during the final stage of the station assembly and provide the Russian segment additional
docking ports to receive Soyuz TMA (transportation modified anthropometric) and Progress M spacecraft.
NM is to be incorporated into the ISS in 2014. It will be integrated with a special version of the Progress
cargo ship and launched by a standard Soyuz rocket. The Progress would use its own propulsion and
flight control system to deliver and dock the Node Module to the nadir (Earth-facing) docking port of the
Nauka MLM/FGB-2 module. One port is equipped with an active hybrid docking port, which enables
docking with the MLM module. The remaining five ports are passive hybrids, enabling docking of Soyuz
and Progress vehicles, as well as heavier modules and future spacecraft with modified docking systems.
However more importantly, the node module was conceived to serve as the only permanent element of
the future Russian successor to the ISS, OPSEK. Equipped with six docking ports, the Node Module
would serve as a single permanent core of the future station with all other modules coming and going as
[113][114]
their life span and mission required. This would be a progression beyond the ISS and Russia's
modular MIR space station, which are in turn more advanced than early monolithic first generation
stations such as Skylab, and early Salyut and Almaz stations.
Science Power Modules 1 & 2 (NEM-1, NEM-2) (Russian: Научно-Энергетический Модуль-1 и -2)
[edit]Cancelled components
The US Habitation Module would have served as the station's living quarters. Instead, the sleep stations
[115]
are now spread throughout the station. The US Interim Control Module and ISS Propulsion
[116]
Module were intended to replace functions of Zvezda in case of a launch failure. The
Russian Universal Docking Module, to which the cancelled Russian Research modules and spacecraft
[117]
would have docked. The Russian Science Power Platform would have provided the Russian Orbital
[117]
Segment with a power supply independent of the ITS solar arrays, and twoRussian Research
[118]
Modules that were planned to be used for scientific research.

25. [edit]Unpressurized elements
ISS Truss Components breakdown showing Trusses and all ORUs in situ
The ISS features a large number of external components that do not require pressurisation. The largest
such component is the Integrated Truss Structure (ITS), to which the station's main solar arrays and
[119]
thermal radiators are mounted. The ITS consists of ten separate segments forming a structure
[3]
108.5 m (356 ft) long.
The station in its complete form has several smaller external components, such as the six robotic arms,
[89][120]
the three External Stowage Platforms (ESPs) and four ExPrESS Logistics Carriers (ELCs). Whilst
these platforms allow experiments (including MISSE, the STP-H3 and the Robotic Refuelling Mission) to
be deployed and conducted in the vacuum of space by providing electricity and processing experimental
data locally, the platforms' primary function is to store Orbital Replacement Units (ORUs). ORUs are
spare parts that can be replaced when the item either passes its design life or fails. Examples of ORUs
include pumps, storage tanks, antennas and battery units. Such units are replaced either by astronauts
during EVA or by robotic arms. While spare parts were routinely transported to and from the station via
Space Shuttle resupply missions, there was a heavy emphasis on ORU transport once the NASA Shuttle
[121]
approached retirement. Several shuttle missions were dedicated to the delivery of ORUs,
[122] [123] [124]
including STS-129, STS-133 and STS-134. To date only one other mode of transportation of
ORUs has been utilised – the Japanese cargo vessel HTV-2 – which delivered an FHRC and CTC-2 via
[125]
its Exposed Pallet (EP).
Construction of the Integrated Truss Structure over New Zealand.

26. There are also smaller exposure facilities mounted directly to laboratory modules; the JEM Exposed
[126]
Facility serves as an external 'porch' for the Japanese Experiment Module complex, and a facility on
the European Columbus laboratory provides power and data connections for experiments such as
[127][128]
the European Technology Exposure Facility and the Atomic Clock Ensemble in
[129]
Space. A remote sensing instrument, SAGE III-ISS, is due to be delivered to the station in 2014
[130]
aboard a Dragon capsule. The largest such scientific payload externally mounted to the ISS is
theAlpha Magnetic Spectrometer (AMS), a particle physics experiment launched on STS-134 in May
2011, and mounted externally on the ITS. The AMS measures cosmic rays to look for evidence of dark
[131]
matter and antimatter.
[edit]Cranes and robotic arms
Canadarm2, the largest robotic arm on the ISS, has a mass of 1,800 kilograms and is used to dock and
manipulate spacecraft and modules on the USOS, and hold crew members and equipment during
[132]
EVAs. The ROS does not require spacecraft or modules to be manipulated, as all spacecraft and
modules dock automatically, and may be discarded the same way. Crew use the
2 Strela (Russian: Стрела; lit. Arrow) cargo cranes during EVAs for moving crew and equipment around
the ROS. Each Strela crane has a mass of 45 kg. The Russian and Japanese laboratories both have
airlocks and robotic arms.
Commander Volkov stands on Pirs with his back to Dextre, like many of the station's experiments and
the Soyuz whilst operating the manual Strela robotic arms, can be operated from Earth and perform
craneholding photographer Kononenko. Zarya is seen tasks while the crew sleeps.
to the left and Zvezda across the bottom of the image.
The Integrated Truss Structure serves as a base for the main remote manipulator system called the
Mobile Servicing System (MSS). This consists of the Mobile Base System (MBS), the Canadarm2,
and Dextre. Dextre is a 1,500 kg agile robotic manipulator with two 'arms' which have 7 degrees of
movement each, a 'torso' which bends at the waist and rotates at the base, a tool holster, lights and
video. Staff on earth can operate Dextre via remote control, performing work without crew intervention.
The MBS rolls along rails built into some of the ITS segments to allow the arm to reach all parts of the
[133]
United States segment of the station. The MSS had its reach increased an Orbiter Boom Sensor
System in May 2011, used to inspect tiles on the NASA shuttle, and converted for permanent station use.
To gain access to the extreme extents of the Russian Segment the crew also placed a "Power Data
Grapple Fixture" to the forward docking section of Zarya, so that the Canadarm2 may inchworm itself onto
[134]
that point.

27. The European Robotic Arm, which will service the Russian Orbital Segment, will be launched alongside
[135]
the Multipurpose Laboratory Module in 2012. The Japanese Experiment Module's Remote Manipulator
[136]
System (JFM RMS), which services the JEM Exposed Facility, was launched on STS-124 and is
[137]
attached to the JEM Pressurised Module.
[edit]Station systems
[edit]Life support
Main articles: ISS ECLSS and Chemical oxygen generator
The critical systems are the atmosphere control system, the water supply system, the food supply
facilities, the sanitation and hygiene equipment, and fire detection and suppression equipment. The
Russian orbital segment's life support systems are contained in the Service Module Zvezda. Some of
these systems are supplemented by equipment in the USOS. The MLM Nauka laboratory has a complete
set of life support systems.
[edit]Atmospheric control systems
[138]
The atmosphere on board the ISS is similar to the Earth's. Normal air pressure on the ISS is
[139]
101.3 kPa (14.7 psi); the same as at sea level on Earth. An Earth-like atmosphere offers benefits for
crew comfort, and is much safer than the alternative, a pure oxygen atmosphere, because of the
[140]
increased risk of a fire such as that responsible for the deaths of the Apollo 1crew. Earth-like
[141]
atmospheric conditions have been maintained on all Russian and Soviet spacecraft.
Elektron units in the Zvezda service module.
The Elektron system aboard Zvezda and a similar system in Destiny generate oxygen aboard the
[142]
station. The crew has a backup option in the form of bottled oxygen and Solid Fuel Oxygen
[143]
Generation (SFOG) canisters, a chemical oxygen generator system. Carbon dioxide is removed from
the air by the Vozdukh system in Zvezda. Other by-products of human metabolism, such as methane
[143]
from the intestines and ammonia from sweat, are removed by activated charcoal filters.
Part of the ROS atmosphere control system is the oxygen supply, triple-redundancy is provided by the
Elektron unit, solid fuel generators, and stored oxygen. The Elektron unit is the primary oxygen
supply, O2 and H2 are produced by electrolysis, with the H2 being vented overboard. The 1 kW system

28. uses approximately 1 litre of water per crew member per day from stored water from Earth, or water
recycled from other systems. MIR was the first spacecraft to use recycled water for oxygen production.
The secondary oxygen supply is provided by burning O2-producing Vika cartridges (see also ISS ECLSS).
Each 'candle' takes 5–20 minutes to decompose at 450–500 °C, producing 600 litres of O2. This unit is
[144]
manually operated.
The US orbital segment has redundant supplies of oxygen, from a pressurised storage tank on the Quest
airlock module delivered in 2001, supplemented ten years later by ESA built Advanced Closed-Loop
[145]
System (ACLS) in the Tranquility module (Node 3), which produces O2by electrolysis. Hydrogen
produced is combined with carbon dioxide from the cabin atmosphere and converted to water and
methane.
[edit]Food
See also: Space food
The crews of STS-127 and Expedition 20enjoy a meal inside Unity.
Most of the food on board is vacuum sealed in plastic bags. Cans are too heavy and expensive to
transport, so there are not as many. The preserved food is generally not held in high regard by the crew,
[146]
and when combined with the reduced sense of taste in a microgravity environment, a great deal of
effort is made to make the food more palatable. More spices are used than in regular cooking, and the
crew looks forward to the arrival of any ships from Earth, as they bring fresh fruit and vegetables with
them. Care is taken that foods do not create crumbs. Sauces are often used to ensure station equipment
is not contaminated. Each crew member has individual food packages and cooks them using the on-
board galley. The galley features two food warmers, a refrigerator added in November 2008, and a water
[147]
dispenser that provides both heated and unheated water. Drinks are provided in dehydrated powder
[147][148]
form and are mixed with water before consumption. Drinks and soups are sipped from plastic bags
with straws, while solid food is eaten with a knife and fork, which are attached to a tray with magnets to
prevent them from floating away. Any food that does float away, including crumbs, must be collected to
[148]
prevent it from clogging up the station's air filters and other equipment.
[edit]Hygiene
[149]:139
Showers on space stations were introduced in the early 1970s on Skylab and Salyut 3. By Salyut 6,
in the early 1980s, the crew complained of the complexity of showering in space, which was a monthly
activity. The ISS does not feature a shower; instead, crewmembers wash using a water jet and wet wipes,

29. with soap dispensed from a toothpaste tube-like container. Crews are also provided with rinseless
[150][151]
shampoo and edible toothpaste to save water.
There are two space toilets on the ISS, both of Russian design, located
[147]
in Zvezda and Tranquility. These Waste and Hygiene Compartments use a fan-driven suction system
similar to the Space Shuttle Waste Collection System. Astronauts first fasten themselves to the toilet seat,
[146]
which is equipped with spring-loaded restraining bars to ensure a good seal. A lever operates a
powerful fan and a suction hole slides open: the air stream carries the waste away. Solid waste is
collected in individual bags which are stored in an aluminium container. Full containers are transferred to
[147][152]
Progress spacecraft for disposal. Liquid waste is evacuated by a hose connected to the front of the
toilet, with anatomically correct "urine funnel adapters" attached to the tube so both men and women can
use the same toilet. Waste is collected and transferred to the Water Recovery System, where it is
[148]
recycled back into drinking water.
[edit]Power and thermal control
Main articles: Electrical system of the International Space Station and External Active Thermal Control
System
Russian solar arrays, backlit by sunset. One of the eight truss mounted pairs of
USOS solar arrays
Double-sided solar, or Photovoltaic arrays, provide electrical power for the ISS. These bifacial cells are
more efficient and operate at a lower temperature than single-sided cells commonly used on Earth, by
[153]
collecting sunlight on one side and light reflected off the Earth on the other.
The Russian segment of the station, like the Space Shuttle and most spacecraft, uses 28 volt DC from
four rotating solar arrays mounted on Zarya and Zvezda. The USOS uses 130–180 V DC from the USOS
PV array, power is stabilised and distributed at 160 V DC and converted to the user-required 124 V DC.
The higher distribution voltageallows smaller, lighter conductors, at the expense of crew safety. The ROS
[119]
uses low voltage. The two station segments share power with converters.
The USOS solar arrays are arranged as four wing pairs, with each wing producing nearly
[119]
32.8 kW. These arrays normally track the sun to maximise power generation. Each array is about
2 2
375 m (450 yd ) in area and 58 metres (63 yd) long. In the complete configuration, the solar arrays track
the sun by rotating the alpha gimbal once per orbit while the beta gimbal follows slower changes in the
angle of the sun to the orbital plane. The Night Glider mode aligns the solar arrays parallel to the ground
[154]
at night to reduce the significant aerodynamic drag at the station's relatively low orbital altitude.

30. The station uses rechargeable nickel-hydrogen batteries (NiH2) for continuous power during the 35
minutes of every 90 minute orbit that it is eclipsed by the Earth. The batteries are recharged on the day
side of the Earth. They have a 6.5 year lifetime (over 37,000 charge/discharge cycles) and will be
[155]
regularly replaced over the anticipated 20-year life of the station.
The station's large solar panels generate a high potential voltage difference between the station and the
ionosphere. This could cause arcing through insulating surfaces and sputtering of conductive surfaces as
ions are accelerated by the spacecraft plasma sheath. To mitigate this, plasma contactor units (PCU)s
[156]
create current paths between the station and the ambient plasma field.
ISS External Active Thermal Control System (EATCS) diagram
The large amount of electrical power consumed by the station's systems and experiments is turned
almost entirely into heat. The heat which can be dissipated through the walls of the stations modules is
insufficient to keep the internal ambient temperature within comfortable, workable limits.Ammonia is
continuously pumped through pipework throughout the station to collect heat, and then into external
radiators exposed to the cold of space, and back into the station.
The International Space Station (ISS) External Active Thermal Control System (EATCS) maintains an
equilibrium when the ISS environment or heat loads exceed the capabilities of the Passive Thermal
Control System (PTCS). Note Elements of the PTCS are external surface materials, insulation such as
MLI, or Heat Pipes. The EATCS provides heat rejection capabilities for all the US pressurised modules,
including the JEM and COF as well as the main power distribution electronics of the S0, S1 and P1
Trusses. The EATCS consists of two independent Loops (Loop A & Loop B), they both use mechanically
pumped Ammonia in fluid state, in closed-loop circuits. The EATCS is capable of rejecting up to 70 kW,
and provides a substantial upgrade in heat rejection capacity from the 14 kW capability of the Early
External Active Thermal Control System (EEATCS) via the Early Ammonia Servicer (EAS), which was
[157]
launched on STS-105 and installed onto the P6 Truss.
[edit]Communications and computers
Main articles: Tracking and Data Relay Satellite and Luch (satellite)
See also: ThinkPad use in space

31. The communications systems used by the ISS
* Luch satellite not currently in use
Radio communications provide telemetry and scientific data links between the station and Mission Control
Centres. Radio links are also used during rendezvous and docking procedures and for audio and video
communication between crewmembers, flight controllers and family members. As a result, the ISS is
[158]
equipped with internal and external communication systems used for different purposes.
The Russian Orbital Segment communicates directly with the ground via the Lira antenna mounted
[15][159]
to Zvezda. The Lira antenna also has the capability to use the Luch data relay satellite
[15]
system. This system, used for communications with Mir, fell into disrepair during the 1990s, and as a
[15][160][161]
result is no longer in use, although two new Luch satellites—Luch-5A and Luch-5B—are planned
[162]
for launch in 2011 to restore the operational capability of the system. Another Russian
communications system is the Voskhod-M, which enables internal telephone communications
between Zvezda, Zarya, Pirs, Poisk and the USOS, and also provides a VHF radio link to ground control
[163]
centres via antennas on Zvezda's exterior.
The US Orbital Segment (USOS) makes use of two separate radio links mounted in the Z1 truss
structure: the S band (used for audio) and Ku band (used for audio, video and data) systems. These
transmissions are routed via the United States Tracking and Data Relay Satellite System (TDRSS)
in geostationary orbit, which allows for almost continuous real-time communications with NASA's Mission
[10][15][158]
Control Center (MCC-H) in Houston. Data channels for the Canadarm2,
European Columbus laboratory and Japanese Kibōmodules are routed via the S band and K u band
systems, although the European Data Relay Satellite System and a similar Japanese system will

32. [10][164]
eventually complement the TDRSS in this role. Communications between modules are carried on
[165]
an internal digitalwireless network.
Laptop computers surround the Canadarm2 console.
UHF radio is used by astronauts and cosmonauts conducting EVAs. UHF is employed by other
spacecraft that dock to or undock from the station, such as Soyuz, Progress, HTV, ATV and the Space
Shuttle (except the shuttle also makes use of the S band and K u band systems via TDRSS), to receive
[15]
commands from Mission Control and ISS crewmembers. Automated spacecraft are fitted with their own
communications equipment; the ATV uses a laser attached to the spacecraft and equipment attached
[166][167]
to Zvezda, known as the Proximity Communications Equipment, to accurately dock to the station.
The ISS is equipped with approximately 100 IBM and Lenovo ThinkPad model A31 and T61P laptop
computers. Each computer is a commercial off-the-shelf purchase which is then modified for safety and
operation including updates to connectors, cooling and power to accommodate the station's 28V DC
power system and weightless environment. Heat generated by the laptops doesn't rise, but stagnates
surrounding the laptop, so additional forced ventilation is required. Laptops aboard the ISS are connected
to the station's wireless LAN via Wi-Fi and are connected to the ground at 3 Mbit/s up and 10 Mbit/s
[168]
down, comparable to home DSL connection speeds.

33. Expeditions and private flights
Soyuz TM-31 being prepared to bring the first resident crew to the station in October 2000
See also the list of professional crew, private travellers, or both
The station crew "are our representatives spearheading humanity's exploration of new spaces and
[169]
possibilities for our future" according to Pope Benedict XVI. Each permanent crew is given an
expedition number. Expeditions run up to six months, from launch until undocking, an 'increment' covers
the same time period, but includes cargo ships and all activities. Expeditions 1 to 6 consisted of 3 person
crews, Expeditions 7 to 12 were reduced to the safe minimum of two following the destruction of the
[170][171]
NASA Shuttle Columbia. From Expedition 13 the crew gradually increased to 6 around 2010. With
the arrival of the American Commercial Crew vehicles in the middle of the 2010s, expedition size may be
[172][173]
increased to seven crew members, the number ISS is designed for.
Sergei Krikalev, member of Expedition 1 and Commander of Expedition 11 has spent more time in space
than anyone else, a total of 803 days and 9 hours and 39 minutes. His awards include the Order of
Lenin, Hero of the Soviet Union, Hero of the Russian Federation, and 4 NASA medals. On 16 August
2005 at 1:44 am EDT he passed the record of 748 days held by Sergei Avdeyev, who had 'time travelled'
[174]
1/50th of a second into the future on board MIR. He participated in psychosocial experiment
SFINCSS-99 (Simulation of Flight of International Crew on Space Station), which examined inter-cultural
and other stress factors effecting integration of crew in preparation for the ISS spaceflights.
Commander Michael Fincke is the U.S. space endurance record holder with a total of 382 days.
Travelers who pay for their own passage into space are called spaceflight participants by the RSA and
[note 1]
NASA, and are sometimes referred to as space tourists, a term they generally dislike. All seven were
transported to the ISS on Russian Soyuz spacecraft. When professional crews change over in numbers
not divisible by the three seats in a Soyuz, and a short-stay crewmember is not sent, the spare seat is
sold by MirCorp through Space Adventures. When the space shuttle retired in 2011, and the station's
crew size was reduced to 6, space tourism was halted, as the partners relied on Russian transport seats
for access to the station. Soyuz flight schedules increase after 2013, allowing 5 Soyuz flights (15 seats)
[180]
with only two expeditions (12 seats) required. The remaining seats are sold for around US$40 million
to members of the public who can pass a medical. ESA and NASA criticised private spaceflight at the
beginning of the ISS, and NASA initially resisted training Dennis Tito, the first man to pay for his own
[note 2]
passage to the ISS. Toyohiro Akiyama was flown to Mir for a week, he was classed as a business
traveller, as his employer, Tokyo Broadcasting System, paid for his ticket, and he gave a daily TV
broadcast from orbit.

34. Anousheh Ansari (Persian: ) became the first Iranian in space and the first self-funded woman
to fly to the station. Officials reported that her education and experience make her much more than a
[181]
tourist, and her performance in training had been "excellent." Ansari herself dismisses the idea that
she is a tourist. She did Russian and European studies involving medicine and microbiology during her 10
day stay. The documentary Space Tourists follows her journey to the station, where she fulfilled the
[182]
childhood dream 'to leave our planet as a normal person and travel into outer space.' In the film, some
Kazakhs are shown waiting in the middle of the steppes for four rocket stages to literally fall from the sky.
Film-maker Christian Frei states "Filming the work of the Kazakh scrap metal collectors was anything but
easy. The Russian authorities finally gave us a film permit in principle, but they imposed crippling
preconditions on our activities. The real daily routine of the scrap metal collectors could definitely not be
shown. Secret service agents and military personnel dressed in overalls and helmets were willing to re-
enact their work for the cameras – in an idealised way that officials in Moscow deemed to be presentable,
but not at all how it takes place in reality."
[edit]Crew activities
NASA astronaut Scott Kelly works on theCombustion Integrated Rack in the Destiny laboratory.
A typical day for the crew begins with a wake-up at 06:00, followed by post-sleep activities and a morning
inspection of the station. The crew then eats breakfast and takes part in a daily planning conference with
Mission Control before starting work at around 08:10. The first scheduled exercise of the day follows,
after which the crew continues work until 13:05. Following a one-hour lunch break, the afternoon consists
of more exercise and work before the crew carries out its pre-sleep activities beginning at 19:30, including
dinner and a crew conference. The scheduled sleep period begins at 21:30. In general, the crew works
ten hours per day on a weekday, and five hours on Saturdays, with the rest of the time their own for
[183]
relaxation or work catch-up.
The station provides crew quarters for each member of the expedition's crew, with two 'sleep stations' in
[184][185]
the Zvezda and four more installed inHarmony. The American quarters are private, approximately
person-sized soundproof booths. The Russian crew quarters include a small window, but do not provide
the same amount of ventilation or block the same amount of noise as their American counterparts. A
crewmember can sleep in a crew quarter in a tethered sleeping bag, listen to music, use a laptop, and
store personal items in a large drawer or in nets attached to the module's walls. The module also provides
[146][147][148]
a reading lamp, a shelf and a desktop. Visiting crews have no allocated sleep module, and
attach a sleeping bag to an available space on a wall—it is possible to sleep floating freely through the
[150]
station, but this is generally avoided because of the possibility of bumping into sensitive equipment. It

35. is important that crew accommodations be well ventilated; otherwise, astronauts can wake up oxygen-
deprived and gasping for air, because a bubble of their own exhaled carbon dioxide has formed around
[146]
their heads.
Orbit and mission control
Graph showing the changing altitude of the ISS from November Animation of ISS orbit from a North American
1998 until January 2009 geostationary point of view (sped up 1800 times)
The ISS is maintained in a nearly circular orbit with a minimum mean altitude of 330 km (205 mi) and a
maximum of 410 km (255 mi), in the centre of the Thermosphere, at an inclination of 51.6 degrees to
Earth's equator, necessary to ensure that Russian Soyuz and Progress spacecraft launched from
the Baikonur Cosmodrome may be safely launched to reach the station. Spent rocket stages must be
dropped into uninhabited areas and this limits the directions rockets can be launched from the
[186][187]
spaceport. The orbital inclination chosen was also low enough to allow American space shuttles
launched from Florida to reach the ISS.
It travels at an average speed of 27,724 kilometres (17,227 mi) per hour, and completes 15.7 orbits per
[20]
day. The station's altitude was allowed to fall around the time of each NASA shuttle mission. Orbital
boost burns would generally be delayed until after the shuttle's departure. This allowed shuttle payloads
to be lifted with the station's engines during the routine firings, rather than have the shuttle lift itself and
the payload together to a higher orbit. This trade-off allowed heavier loads to be transferred to the station.
After the retirement of the NASA shuttle, the nominal orbit of the space station was raised in
[188][189]
altitude. Other, more frequent supply ships do not require this adjustment as they are substantially
[27][190]
lighter vehicles.
Orbital boosting can be performed by the station's two main engines on the Zvezda service module, or
Russian or European spacecraft docked to Zvezda's aft port. The ATV has been designed with the
possibility of adding a second docking port to its other end, allowing it to remain at the ISS and still allow
other craft to dock and boost the station. It takes approximately two orbits (three hours) for the boost to a
[190]
higher altitude to be completed. In December 2008 NASA signed an agreement with the Ad Astra
Rocket Company which may result in the testing on the ISS of aVASIMR plasma propulsion
[191]
engine. This technology could allow station-keeping to be done more economically than at
[192][193]
present.

36. The Russian Orbital Segment contains the station's engines and control bridge, which handles Guidance,
[91]
Navigation and Control (ROS GNC) for the entire station. Initially, Zarya, the first module of the station,
controlled the station until a short time after the Russian service module Zvezda docked and was
[194]
transferred control. Zvezda contains the ESA built DMS-R Data Management System. Using two fault-
tolerant computers (FTC), Zvezda computes the station's position and orbital trajectory using redundant
Earth horizon sensors, Solar horizon sensors as well as Sun and star trackers. The FTCs each contain
three identical processing units working in parallel and provide advanced fault-masking by majority voting.
Zvezda uses gyroscopes and thrusters to turn itself around. Gyroscopes don't need propellant, rather
they use electricity to 'store' momentum in flywheels by turning in the opposite direction to the station's
movement. The USOS has its own computer controlled gyroscopes to handle the extra mass of that
section. When gyroscopes 'saturate', reaching their maximum speed, thrusters are used to cancel out the
stored momentum. During Expedition 10, an incorrect command was sent to the station's computer, using
about 14 kilograms of propellant before the fault was noticed and fixed. When attitude control computers
in the ROS and USOS don't communicate properly, it can result in a rare 'force fight' where the ROS GNC
[195][196][197]
computer must ignore the USOS counterpart, which has no thrusters. When an ATV, Nasa
Shuttle, or Soyuz is docked to the station, it can also be used to maintain station attitude such as for
troubleshooting. Shuttle control was used exclusively during installation of the S3/S4 truss, which
[198]
provides electrical power and data interfaces for the station's electronics.
Space centres involved with the ISS programme
The components of the ISS are operated and monitored by their respective space agencies at mission
control centres across the globe, including:

37. Roskosmos's Mission Control Center at Korolyov, Moscow Oblast, controls the Russian Orbital
[91][194]
Segment which handles Guidance, Navigation & Control for the entire Station., in addition to
[15]
individual Soyuz and Progress missions.
ESA's ATV Control Centre, at the Toulouse Space Centre (CST) in Toulouse, France, controls flights
[15]
of the unmanned European Automated Transfer Vehicle.
JAXA's JEM Control Centre and HTV Control Centre at Tsukuba Space Centre (TKSC) in Tsukuba,
Japan, are responsible for operating the Japanese Experiment Module complex and all flights of the
[15]
'White Stork' HTV Cargo spacecraft, respectively.
NASA's Mission Control Center at Lyndon B. Johnson Space Center in Houston, Texas, serves as
the primary control facility for the United States segment of the ISS and also controlled the Space
[15]
Shuttle missions that visited the station.
NASA's Payload Operations and Integration Center at Marshall Space Flight Center in Huntsville,
[15]
Alabama, coordinates payload operations in the USOS.
ESA's Columbus Control Centre at the German Aerospace Centre (DLR) in Oberpfaffenhofen,
[15]
Germany, manages the European Columbus research laboratory.
CSA's MSS Control at Saint-Hubert, Quebec, Canada, controls and monitors the Mobile Servicing
[15]
System, or Canadarm2.
[edit]Repairs
Main articles: Orbital Replacement Units and International Space Station maintenance
Orbital Replacement Units (ORUs) are spare parts that can be readily replaced when a unit either
passes its design life or fails. Examples of ORUs are pumps, storage tanks, controller boxes, antennas,
and battery units. Some units can be replaced using robotic arms. Many are stored outside the station,
either on small pallets called ExPRESS Logistics Carriers (ELCs) or share larger platforms called External
Stowage Platforms which also hold science experiments. Both kinds of pallets have electricity as many
parts which could be damaged by the cold of space require heating. The larger logistics carriers also
have computer local area network connections (LAN) and telemetry to connect experiments. A heavy
emphasis on stocking the USOS with ORU's occurred around 2011, before the end of the NASA shuttle
program, as its commercial replacements, Cygnus and Dragon, carry one tenth to one quarter the
payload.
Spare parts are called ORU's, some are externally stored on pallets called ELC's and ESP's.
Unexpected problems and failures have impacted the station's assembly time-line and work schedules
leading to periods of reduced capabilities and, in some cases, could have forced abandonment of the