The International Space Station
The International Space Station is the biggest object ever flown in space. It travels around the Earth at an average speed of 27,700 km/h, completing 16 orbits per day. At night it can easily be seen from Earth, as it flies 320 kilometres above us. 16 countries, including the USA, Russia, Japan, Canada and many ESA member states worked together to build the Station.
The largest part of the ISS is a central truss to which 16 huge solar panels are attached. The modules where the astronauts live and work are attached to the centre of the truss. Europe’s biggest ISS project is the Columbus science laboratory, where astronauts can carry out scientific experiments in weightless conditions. Many different types of experiments can take place both inside and outside this space laboratory.
ESA also makes the Automated Transfer Vehicle (ATV), a series of uncrewed spacecraft designed to take supplies to the ISS. The cargo craft delivers food, fuel, equipment and other supplies.
"ISS" redirects here. For other uses, see ISS (disambiguation).
The International Space Station on 23 May 2010 as seen from the departing Space ShuttleAtlantis during STS-132.
|Call sign||Alpha, Station|
|Crew||Fully crewed: 6|
Currently aboard: 6
|Launch||20 November 1998 (1998-11-20)|
|Mass||≈ 419,455 kg (924,740 lb)|
|Length||72.8 m (239 ft)|
|Width||108.5 m (356 ft)|
|Height||≈ 20 m (66 ft)|
nadir–zenith, arrays forward–aft
(27 November 2009)[needs update]
|Pressurised volume||931.57 m3 (32,898 cu ft)|
(28 May 2016)
|Atmospheric pressure||101.3 kPa (29.9 inHg; 1.0 atm)|
|Perigee||401.1 km (249.2 mi) AMSL|
|Apogee||408.0 km (253.5 mi) AMSL|
|Orbital inclination||51.64 degrees|
|Orbital speed||7.67 km/s|
(27,600 km/h; 17,200 mph)
|Orbital period||92.65 minutes|
|Orbits per day||15.54|
|Orbit epoch||7 July 2017, 13:10:09 UTC|
|Days in orbit||19 years, 3 months, 22 days|
(14 March 2018)
|Days occupied||17 years, 4 months, 12 days|
(14 March 2018)
|No. of orbits||102,491 as of July 2017[update]|
|Orbital decay||2 km/month|
|Statistics as of 9 March 2011|
(unless noted otherwise)
Station elements as of June 2017[update]
The International Space Station (ISS) is a space station, or a habitable artificial satellite, in low Earth orbit. Its first component launched into orbit in 1998, the last pressurised module was fitted in 2011, and the station is expected to be used until 2028. Development and assembly of the station continues, with components scheduled for launch in 2018 and 2019. The ISS is the largest human-made body in low Earth orbit and can often be seen with the naked eye from Earth. The ISS consists of pressurised modules, external trusses, solar arrays, and other components. ISS components have been launched by Russian Proton and Soyuz rockets, and American Space Shuttles.
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. The station is suited for the testing of spacecraft systems and equipment required for missions to the Moon and Mars. The ISS maintains an orbit with an altitude of between 330 and 435 km (205 and 270 mi) by means of reboost manoeuvres using the engines of the Zvezda module or visiting spacecraft. It completes 15.54 orbits per day.
The ISS programme is a joint project among five participating space agencies: NASA, Roscosmos, JAXA, ESA, and CSA. The ownership and use of the space station is 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. As of January 2014[update], the American portion of ISS is being funded until 2024. Roscosmos has endorsed the continued operation of ISS through 2024 but has proposed using elements of the Russian Orbital Segment to construct a new Russian space station called OPSEK.
The ISS is the ninth space station to be inhabited by crews, following the Soviet and later Russian Salyut, Almaz, and Mir stations as well as Skylab from the US. The station has been continuously occupied for 17 years and 132 days since the arrival of Expedition 1 on 2 November 2000. This is the longest continuous human presence in low Earth orbit, having surpassed the previous record of 9 years and 357 days held by Mir. The station is serviced by a variety of visiting spacecraft: the Russian Soyuz and Progress, the American Dragon and Cygnus, the Japanese H-II Transfer Vehicle, and formerly the Space Shuttle and the European Automated Transfer Vehicle. It has been visited by astronauts, cosmonauts and space tourists from 17 different nations.
After the U.S. Space Shuttle programme ended in 2011, Soyuz rockets became the only provider of transport for astronauts at the International Space Station, and Dragon became the only provider of bulk cargo return to Earth (called downmass). Soyuz has very limited downmass capability.
On 28 March 2015, Russian sources announced that Roscosmos and NASA had agreed to collaborate on the development of a replacement for the current ISS. NASA later issued a guarded statement expressing thanks for Russia's interest in future co-operation in space exploration but fell short of confirming the Russian announcement.
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 low Earth orbit. It was also planned to provide transportation, maintenance, and act as a staging base for possible future missions to the Moon, Mars and asteroids. In the 2010 United States National Space Policy, the ISS was given additional roles of serving commercial, diplomatic and educational purposes.
Main article: Scientific research on the ISS
The ISS provides a platform to conduct scientific research. Small unmanned spacecraft can provide platforms for zero gravity and exposure to space, but 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.
The ISS simplifies individual experiments by eliminating the need for separate rocket launches and research staff. The wide variety of research fields include astrobiology, astronomy, human research including space medicine and life sciences, physical sciences, materials science, space weather, and weather on Earth (meteorology). Scientists on Earth have access to the crew's data and can modify experiments or launch new ones, which are benefits generally unavailable on unmanned spacecraft. Crews fly expeditions of several months duration, providing approximately 160-man-hours per week of labour with a crew of 6.
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 space telescope, and says could not be accommodated on a free flying satellite platform partly because of its power requirements and data bandwidth needs. On 3 April 2013, NASA scientists reported that hints of dark matter may have been detected by the Alpha Magnetic Spectrometer. 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."
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. Some simple forms 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[update], 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. 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.
The Earth's gravity is only slightly weaker at the altitude of the ISS than at the surface, but objects 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:
- 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 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.
Investigating the physics of fluids in microgravity will provide better models of the behaviour of fluids. Because fluids can be almost completely combined in microgravity, physicists investigate fluids that do not mix well on Earth. In addition, examining reactions that are slowed by low gravity and low temperatures will improve our understanding of superconductivity.
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. 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.
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. 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". 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.
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."A manned mission to Mars may be a multinational effort involving space agencies and countries outside the current ISS partnership. In 2010, ESA Director-General Jean-Jacques Dordain stated his agency was ready to propose to the other four partners that China, India and South Korea be invited to join the ISS partnership. NASA chief Charlie Bolden stated in February 2011, "Any mission to Mars is likely to be a global effort". Currently, American legislation prevents NASA co-operation with China on space projects.
Education and cultural outreach
The ISS crew provides 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. ESA offers a wide 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 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 their responsibilities in society." 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. 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.
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."
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 nine 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.
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. The film was streamed through the website firstorbit.org in a global YouTube premiere in 2011, under a free license.
In May 2013, commander Chris Hadfield shot a music video of David Bowie's "Space Oddity" on board the station; the film was released on YouTube. It was the first music video ever to be filmed in space.
In November 2017, while participating in Expedition 52/53 on the ISS, Paolo Nespoli made two recordings (one in English the other in his native Italian) of his spoken voice, for use on Wikipedia articles. These were the first content made specifically for Wikipedia, in space.
Main articles: Assembly of the International Space Station and List of ISS spacewalks
The assembly of the International Space Station, a major endeavour in space architecture, began in 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 Canadarm2 (SSRMS) and extra-vehicular activities (EVAs); as of 5 June 2011[update], they had added 159 components during more than 1,000 hours of EVA (see List of ISS spacewalks). 127 of these spacewalks originated from the station, and the 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 it directly affects how long during its orbit the station (and any docked or docking spacecraft) is exposed to the sun; the Space Shuttle would not perform optimally above a limit called the "beta cutoff". Many of the modules that launched on the Space Shuttle were integrated and tested on the ground at the Space Station Processing Facility to find and correct issues prior to launch.
The first module of the ISS, Zarya, was launched on 20 November 1998 on an autonomous Russian Proton rocket. It provided propulsion, attitude 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 that time, the Russian station Mir was still inhabited. The ISS remained unmanned for two years, while 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 target for a rendezvous with Zarya and Unity: it maintained a station-keeping orbit while 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. This enabled permanent habitation of the station.
The first resident crew, Expedition 1, arrived in November 2000 on Soyuz TM-31. At the end of the first day on the station, astronaut Bill Shepherd requested the use of the radio call sign "Alpha", which he and cosmonaut Krikalev preferred to the more cumbersome "International Space Station". The name "Alpha" had previously been used for the station in the early 1990s, and following the request, its use was authorised for the whole of Expedition 1. Shepherd had been advocating the use of a new name to project managers for some time. Referencing a naval tradition in a pre-launch news conference he had said: "For thousands of years, humans have been going to sea in ships. People have designed and built these vessels, launched them with a good feeling that a name will bring good fortune to the crew and success to their voyage."Yuri Semenov, the President of Russian Space Corporation Energia at the time, disapproved of the name "Alpha"; he felt that Mir was the first space station, and so he would have preferred the names "Beta" or "Mir 2" for the ISS.
Expedition 1 arrived 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 US television, additional attitude support needed for the additional mass of the USOS, and substantial solar arrays supplementing the station's existing 4 solar arrays.
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 Space ShuttleColumbiadisaster in 2003 and a resulting two-year hiatus in the Space Shuttle programme. The space shuttle was grounded until 2005 with STS-114 flown by Discovery.
Assembly resumed in 2006 with the arrival of STS-115 with Atlantis, 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 soon followed 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, followed in May 2010 by the penultimate Russian module, Rassvet. Rassvet was delivered by Space Shuttle Atlantis on STS-132 in exchange for the Russian Proton delivery of the Zarya module in 1998 which had been funded by the United States. The last pressurised module of the USOS, Leonardo, was brought to the station by Discovery on her final flight, STS-133, in February 2011. The Alpha Magnetic Spectrometer was delivered by Endeavour on STS-134 the same year.
As of June 2011[update], the station consisted of 15 pressurised modules and the Integrated Truss Structure. Five modules are still to be launched, including the Nauka with the European Robotic Arm, the Uzlovoy Module, and two power modules called NEM-1 and NEM-2. As of August 2017[update], Russia's future primary research module Nauka is set to launch in the first quarter of 2018, along with the European Robotic Arm which will be able to relocate itself to different parts of the Russian modules of the station. After the Nauka module is attached, the Uzlovoy Module will be attached to one of its docking ports. When completed, the station will have a mass of more than 400 tonnes (440 short tons).
The gross mass of the station changes over time. The total launch mass of the modules on orbit is about 417,289 kg (919,965 lb) (as of 3 September 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. Hydrogen gas is constantly vented overboard by the oxygen generators.
The ISS is a third generation modular space station. 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 Orbital Segment Windows
USOS International Space Station window locations