International Space Station

International Space Station

International Space Station

The International Space Station, as seen from Space Shuttle Endeavour in May 2011.
ISS insignia
Station statistics
COSPAR ID	1998-067A
Call sign	Alpha
Crew	Fully crewed 6 Currently aboard 6 (Expedition 36)
Launch	1998–2020
Launch pad	Baikonur 1/5 and 81/23 Kennedy LC-39
Mass	approximately 450,000 kg (990,000 lb)
Length	72.8 m (239 ft)
Width	108.5 m (356 ft)
Height	c. 20 m (c. 66 ft) nadir–zenith, arrays forward–aft (27 November 2009)[dated info]
Pressurised volume	837 m3 (29,600 cu ft) (21 March 2011)
Atmospheric pressure	101.3 kPa (29.91 inHg, 1 atm)
Perigee	413 km (257 mi) AMSL[1]
Apogee	418 km (260 mi) AMSL[1]
Orbital inclination	51.65 degrees[1]
Average speed	7.67 kilometres per second (27,600 km/h; 17,200 mph)[1]
Orbital period	92.88 minutes[1]
Orbit epoch	7 September 2013[1]
Days in orbit	5406 (8 September)
Days occupied	4693 (8 September)
Number of orbits	84,745[1]
Orbital decay	2 km/month
Statistics as of 9 March 2011 (unless noted otherwise)
References: [1][2][3][4][5][6]
Configuration
Station elements as of December 2011, but missing Pirs (exploded view)

The International Space Station (ISS) is a space station, or a habitable artificial satellite in low Earth orbit. The ninth space station to be inhabited by crews, it follows the Soviet and later Russian Salyut, Almaz, and Mir stations, and America's Skylab. The ISS is a modular structure whose first component was launched in 1998.^[7] Now the largest artificial body in orbit, it can often be seen at the appropriate time with the naked eye from Earth.^[8] The ISS consists of pressurised modules, external trusses, solar arrays and other components. ISS components have been launched by American Space Shuttles as well as Russian Proton and Soyuz rockets.^[9] Budget constraints led to the merger of three space station projects with the Japanese Kibō module and Canadian robotics. In 1993 the partially built components for a Soviet/Russian space station Mir-2, the proposed American Freedom, and the proposed European Columbus merged into a single multinational programme.^[9] The ISS is arguably the most expensive single item ever constructed.^[10]

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 fields.^[11][12][13] The station is suited for the testing of spacecraft systems and equipment required for missions to the Moon and Mars.^[14]

Since the arrival of Expedition 1 on 2 November 2000, the station has been continuously occupied for 12 years and 310 days, currently the longest continuous human presence in space. (In 2010, the station surpassed the previous record of almost 10 years (or 3,634 days) held by Mir.) The station is serviced by Soyuz spacecraft, Progress spacecraft, the Automated Transfer Vehicle, the H-II Transfer Vehicle,^[15] and the Dragon spacecraft. It has been visited by astronauts and cosmonauts from 15 different nations.^[16]

The ISS programme is a joint project among five participating space agencies: NASA, Roskosmos, JAXA, ESA, and CSA.^[15][17] The ownership and use of the space station is established by intergovernmental treaties and agreements.^[18] 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 maintains an orbit with an altitude of between 330 km (205 mi) and 435 km (270 mi) by means of reboost manoeuvres using the engines of the Zvezda module or visiting spacecraft. It completes 15.50 orbits per day.^[19] The ISS is funded until 2020, and may operate until 2028.^[20][21][22] The Russian Federal Space Agency, Roskosmos (RKA) has proposed using the ISS to commission modules for a new space station, called OPSEK, before the remainder of the ISS is deorbited.

Purpose

According to the original Memorandum of Understanding between NASA and Rosaviakosmos, 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, Mars and asteroids.^[23] In the 2010 United States National Space Policy, the ISS was given additional roles of serving commercial, diplomatic^[24] and educational purposes.^[25]

Scientific research

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 spacecraft.^[16][26]

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 weather and weather on Earth (meteorology).^{[11][12][13][27][28]} Scientists on Earth have access to the crew's data and can modify experiments or launch new ones, benefits generally unavailable on unmanned spacecraft.^[26] Crews fly expeditions of several months duration, providing approximately 160 man-hours a week of labour with a crew of 6.^[11][29]

Kibō is intended to accelerate Japan's progress in science and technology, gain new knowledge and apply it to such fields as industry and medicine.^[30]

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 to its power requirements and data bandwidth needs.^[31][32] On 3 April 2013, NASA scientists reported that hints of dark matter may have been detected by the Alpha Magnetic Spectrometer.^{[33][34][35][36][37][38]} According to the scientists, "The first results from the space-borne Alpha Magnetic Spectrometer confirm an unexplained excess of high-energy positrons in Earth-bound cosmic rays."

Comet Lovejoy photographed by Expedition 30 commander Dan Burbank		Expedition 8 Commander and Science Officer Michael Foale conducts an inspection of the Microgravity Science Glovebox

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, in addition to cosmic rays), high vacuum, extreme temperatures, and microgravity.^[39] Some simple forms of life called extremophiles,^[40] including small invertebrates called tardigrades^[41] 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 required to travel to Mars.^[42][43] 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 situations where access to a trained physician is difficult.^[44][45][46]

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)

The Earth's gravity is only slightly weaker at the altitude of the ISS than at the surface, however object in orbit are in a continuous state of freefall, resulting in an apparent state of weightlessness. This perceived weightlessness is disturbed by five separate effects:^[47]

• 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.
• Vibration from movements of mechanical systems and the crew.
• Actuation of the on-board attitude control moment gyroscopes.
• Thruster firings for attitude or orbital changes.
• Gravity-gradient effects, also known as tidal effects. Items at different locations within the ISS would, if not attached to the station, follow slightly different orbits. Being mechanically interconnected, however, these items experience small forces that keep the station moving as a rigid body.

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, and the unusual protein crystals that can be formed in space.^[12]

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 and temperatures will give scientists a deeper understanding of superconductivity.^[12]

The study of materials science is an important ISS research activity, with the objective of reaping economic benefits through the improvement of techniques used on the ground.^[48] 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 oxides in Earth's atmosphere, as well as cosmic rays, cosmic dust, antimatter, and dark matter in the universe.^[12]

Exploration

A 3D plan of the Russia-based MARS-500 complex, used for ground-based experiments which complement ISS-based preparations for a manned 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 operating spacecraft farther from Earth, mission risks can be reduced and the capabilities of interplanetary spacecraft advanced.^[14] Referring to the MARS-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 more appropriately addressed via ground-based simulations".^[49] Sergey Krasnov, the head of human space flight programmes for Russia's space agency, Roscosmos, in 2011 suggested a "shorter version" of MARS-500 may be carried out on the ISS. ^[50]

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 the Solar system, including the Moon and Mars."^[51] 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 partners that China, India and South Korea be invited to join the ISS partnership.^[52] NASA chief Charlie Bolden stated in Feb 2011 "Any mission to Mars is likely to be a global effort".^[53] Currently, American legislation prevents NASA co-operation with China on space projects.^[54]

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 experiments, and directly engaging students using radio, videolink and email.^[15][55] ESA offers a wide range of free teaching materials that can be downloaded for use in classrooms.^[56] In one lesson, students can navigate a 3-D model of the interior and exterior of the ISS, and face spontaneous challenges to solve in real time.^[57]

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 their responsibilities in society."^[58] Through a series of education guides, a deeper understanding of the past and near-term future of manned space flight, as well as that of Earth and life, will be learned.^[59][60] 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 than a dozen Japanese universities conducted experiments in diverse fields.^[61]

Susan J. Helms, Expedition Two flight engineer, talks to amateur radio operators on Earth from the Amateur radio workstation in the Zarya.		A student speaks to crew using Amateur Radio, 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 in science."^[30]

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 students to ground stations which then connect the calls to the station. ^[62]

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 documentary film, and as a result is credited as its director of photography.^[63] The film was streamed through the website www.firstorbit.org in a global YouTube premiere in 2011, under a free license.^[64]

In May 2013, commander Chris Hadfield shot a music video of David Bowie's Space Oddity on board the station; the film was released freely on YouTube.^[65] It was the first music video ever to be filmed in space.^[66]

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 programme, 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 US-led project, thereby preventing those nations from becoming major, independent competitors too.^[67]

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 Space Station.^[68] They also agreed, in preparation for this new project, that the United States would be involved in the Mir programme, including American Shuttles docking, in the Shuttle–Mir Programme.^[69]

Mir-2

The Soviet Buran spacecraft would have carried modules up to 30 tons^[which?] to MIR-2. 80–100 ton modules could have used the Energia rocket without the orbiter.

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 Energia's core stage and boosters worked properly, however the Polyus spacecraft fired its engines to insert itself into orbit whilst in an incorrect orientation 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 internal equipment was installed by October 1986.^[70]

The Polyus module or spacecraft would have served as the FGB,^{[citation needed]} 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 metres (121 ft) and a diameter of 4.1 metres (13 ft), with a mass of nearly 80 t^[which?], and included two principal sections, the smallest, the functional service block (FGB), and the largest, the aim module.^{[clarification needed][71]}

In 1983, the design was changed and the station would consist of Zvezda, followed by several 90 tonne 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 assembly of the station was expected to begin in 1993.^[70] 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.