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71-501: SES-5 (also known as Astra 4B and Sirius 5 ) is a commercial geostationary communication satellite operated by SES It was launched on 9 July 2012. The launch was arranged by International Launch Services (ILS). In October 2008, SES Sirius AB of Sweden (then 90% owned by SES and prior to 2003 called Nordic Satellite AB) ordered the Sirius 5 satellite from Space Systems/Loral . Following full acquisition by SES in 2010, SES Sirius

142-479: A delta-v of approximately 50 m/s per year. A second effect to be taken into account is the longitudinal drift, caused by the asymmetry of the Earth – the equator is slightly elliptical ( equatorial eccentricity ). There are two stable equilibrium points sometimes called "gravitational wells" (at 75.3°E and 108°W) and two corresponding unstable points (at 165.3°E and 14.7°W). Any geostationary object placed between

213-427: A geostationary transfer orbit (GTO), an elliptical orbit with an apogee at GEO height and a low perigee . On-board satellite propulsion is then used to raise the perigee, circularise and reach GEO. Satellites in geostationary orbit must all occupy a single ring above the equator . The requirement to space these satellites apart, to avoid harmful radio-frequency interference during operations, means that there are

284-452: A temporary orbit , and placed in a slot above a particular point on the Earth's surface. The orbit requires some stationkeeping to keep its position, and modern retired satellites are placed in a higher graveyard orbit to avoid collisions. In 1929, Herman Potočnik described both geosynchronous orbits in general and the special case of the geostationary Earth orbit in particular as useful orbits for space stations . The first appearance of

355-525: A geostationary orbit in popular literature was in October 1942, in the first Venus Equilateral story by George O. Smith , but Smith did not go into details. British science fiction author Arthur C. Clarke popularised and expanded the concept in a 1945 paper entitled Extra-Terrestrial Relays – Can Rocket Stations Give Worldwide Radio Coverage? , published in Wireless World magazine. Clarke acknowledged

426-415: A geostationary orbit in particular, it ensures that it holds the same longitude over time. This orbital period, T , is directly related to the semi-major axis of the orbit through the formula: where: The eccentricity is zero, which produces a circular orbit . This ensures that the satellite does not move closer or further away from the Earth, which would cause it to track backwards and forwards across

497-518: A geostationary orbit was Syncom 3 , which was launched by a Delta D rocket in 1964. With its increased bandwidth, this satellite was able to transmit live coverage of the Summer Olympics from Japan to America. Geostationary orbits have been in common use ever since, in particular for satellite television. Today there are hundreds of geostationary satellites providing remote sensing and communications. Although most populated land locations on

568-399: A known position) and providing an additional reference signal. This improves position accuracy from approximately 5m to 1m or less. Past and current navigation systems that use geostationary satellites include: Geostationary satellites are launched to the east into a prograde orbit that matches the rotation rate of the equator. The smallest inclination that a satellite can be launched into

639-408: A large area of the earth's surface, extending 81° away in latitude and 77° in longitude. They appear stationary in the sky, which eliminates the need for ground stations to have movable antennas. This means that Earth-based observers can erect small, cheap and stationary antennas that are always directed at the desired satellite. However, latency becomes significant as it takes about 240 ms for

710-501: A limited number of orbital slots available, and thus only a limited number of satellites can be operated in geostationary orbit. This has led to conflict between different countries wishing access to the same orbital slots (countries near the same longitude but differing latitudes ) and radio frequencies . These disputes are addressed through the International Telecommunication Union 's allocation mechanism under

781-702: A longer lifetime at the cost of requiring regular support launches. The ISS is divided into two main sections, the Russian Orbital Segment (ROS) and the US Orbital Segment (USOS). The first module of the ISS, Zarya , was launched in 1998. The Russian Orbital Segment's "second-generation" modules were able to launch on Proton , fly to the correct orbit, and dock themselves without human intervention. Connections are automatically made for power, data, gases, and propellants. The Russian autonomous approach allows

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852-458: A second crew to visit, bringing a new spacecraft with them; the Soyuz ferry could spend 90 days in space, at which point it needed to be replaced by a fresh Soyuz spacecraft. This allowed for a crew to man the station continually. The American Skylab (1973–1979) was also equipped with two docking ports, like second-generation stations, but the extra port was never used. The presence of a second port on

923-406: A signal to pass from a ground based transmitter on the equator to the satellite and back again. This delay presents problems for latency-sensitive applications such as voice communication, so geostationary communication satellites are primarily used for unidirectional entertainment and applications where low latency alternatives are not available. Geostationary satellites are directly overhead at

994-564: A space station occurred in Edward Everett Hale 's 1868 " The Brick Moon ". The first to give serious, scientifically grounded consideration to space stations were Konstantin Tsiolkovsky and Hermann Oberth about two decades apart in the early 20th century. In 1929, Herman Potočnik 's The Problem of Space Travel was published, the first to envision a "rotating wheel" space station to create artificial gravity . Conceptualized during

1065-579: A variety of challenges to human habitability, including short-term problems such as the limited supplies of air, water, and food and the need to manage waste heat , and long-term ones such as weightlessness and relatively high levels of ionizing radiation . These conditions can create long-term health problems for space-station inhabitants, including muscle atrophy , bone deterioration , balance disorders , eyesight disorders , and elevated risk of cancer . Future space habitats may attempt to address these issues, and could be designed for occupation beyond

1136-477: A year, all aboard Mir . Many spacecraft are used to dock with the space stations. Soyuz flight T-15 in March to July 1986 was the first and as of 2016, only spacecraft to visit two different space stations, Mir and Salyut 7 . The International Space Station has been supported by many different spacecraft. The Tiangong space station is supported by the following spacecraft: The Tiangong program relied on

1207-562: Is a complex vehicle that must incorporate many interrelated subsystems, including structure, electrical power, thermal control, attitude determination and control , orbital navigation and propulsion, automation and robotics, computing and communications, environmental and life support, crew facilities, and crew and cargo transportation. Stations must serve a useful role, which drives the capabilities required. Space stations are made from durable materials that have to weather space radiation , internal pressure, micrometeoroids , thermal effects of

1278-502: Is also carrying a hosted payload L-band navigation terminal for the executive commission of the 27-nation European Union . The terminal operated as part of the European Geostationary Navigation Overlay Service (EGNOS) system, which provides verification of Global Positioning System (GPS) navigation signals through the use of satellites in geostationary orbit. Sirius 5 was the original name of

1349-535: Is not designed for disassembly and must be deorbited as one mass. The Axiom Orbital Segment is a planned commercial segment to be added to the ISS starting in the mid-2020s. Axiom Space gained NASA approval for the venture in January 2020. Up to three Axiom modules will attach to the International Space Station. The first module, Hab One, is expected to be launched at the end of 2026 and will be docked to

1420-452: Is that of the launch site's latitude, so launching the satellite from close to the equator limits the amount of inclination change needed later. Additionally, launching from close to the equator allows the speed of the Earth's rotation to give the satellite a boost. A launch site should have water or deserts to the east, so any failed rockets do not fall on a populated area. Most launch vehicles place geostationary satellites directly into

1491-403: Is the gravitational constant , (6.674 28 ± 0.000 67 ) × 10  m kg s . The magnitude of the acceleration, a , of a body moving in a circle is given by: where v is the magnitude of the velocity (i.e. the speed) of the satellite. From Newton's second law of motion , the centripetal force F c is given by: As F c = F g , so that Replacing v with the equation for

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1562-781: Is typically 70°, and in some cases less. Geostationary satellite imagery has been used for tracking volcanic ash , measuring cloud top temperatures and water vapour, oceanography , measuring land temperature and vegetation coverage, facilitating cyclone path prediction, and providing real time cloud coverage and other tracking data. Some information has been incorporated into meteorological prediction models , but due to their wide field of view, full-time monitoring and lower resolution, geostationary weather satellite images are primarily used for short-term and real-time forecasting. Geostationary satellites can be used to augment GNSS systems by relaying clock , ephemeris and ionospheric error corrections (calculated from ground stations of

1633-408: Is used to provide visible and infrared images of Earth's surface and atmosphere for weather observation, oceanography , and atmospheric tracking. As of 2019 there are 19 satellites in either operation or stand-by. These satellite systems include: These satellites typically capture images in the visual and infrared spectrum with a spatial resolution between 0.5 and 4 square kilometres. The coverage

1704-502: The Gemini program paved the way and achieved the first space rendezvous (undocked) with Gemini 6 and Gemini 7 in 1965. Subsequently in 1966 Neil Armstrong performed on Gemini 8 the first ever space docking, while in 1967 Kosmos 186 and Kosmos 188 were the first spacecrafts that docked automatically. In January 1969, Soyuz 4 and Soyuz 5 performed the first docked, but not internal, crew transfer, and in March, Apollo 9 performed

1775-473: The Radio Regulations . In the 1976 Bogota Declaration , eight countries located on the Earth's equator claimed sovereignty over the geostationary orbits above their territory, but the claims gained no international recognition. A statite is a hypothetical satellite that uses radiation pressure from the sun against a solar sail to modify its orbit. It would hold its location over the dark side of

1846-668: The Salyut successor Mir . Uninterrupted occupation of stations has been achieved since the operational transition from the Mir to the ISS , with its first occupation in 2000. The ISS has hosted the highest number of people in orbit at the same time, reaching 13 for the first time during the eleven day docking of STS-127 in 2009. The duration record for a single spaceflight is 437.75 days, set by Valeri Polyakov aboard Mir from 1994 to 1995. As of 2021 , four cosmonauts have completed single missions of over

1917-552: The Second World War , the " sun gun " was a theoretical orbital weapon orbiting Earth at a height of 8,200 kilometres (5,100 mi). No further research was ever conducted. In 1951, Wernher von Braun published a concept for a rotating wheel space station in Collier's Weekly , referencing Potočnik's idea. However, development of a rotating station was never begun in the 20th century. The first human flew to space and concluded

1988-430: The centripetal force required to maintain the orbit ( F c ) is equal to the gravitational force acting on the satellite ( F g ): From Isaac Newton 's universal law of gravitation , where F g is the gravitational force acting between two objects, M E is the mass of the Earth, 5.9736 × 10  kg , m s is the mass of the satellite, r is the distance between the centers of their masses , and G

2059-451: The direction of Earth's rotation . An object in such an orbit has an orbital period equal to Earth's rotational period, one sidereal day , and so to ground observers it appears motionless, in a fixed position in the sky. The concept of a geostationary orbit was popularised by the science fiction writer Arthur C. Clarke in the 1940s as a way to revolutionise telecommunications, and the first satellite to be placed in this kind of orbit

2130-442: The speed of an object moving around a circle produces: where T is the orbital period (i.e. one sidereal day), and is equal to 86 164 .090 54  s . This gives an equation for r : The product GM E is known with much greater precision than either factor alone; it is known as the geocentric gravitational constant μ = 398 600 .4418 ± 0.0008 km s . Hence Space station Space stations have been hosting

2201-424: The Earth at a latitude of approximately 30 degrees. A statite is stationary relative to the Earth and Sun system rather than compared to surface of the Earth, and could ease congestion in the geostationary ring. Geostationary satellites require some station keeping to keep their position, and once they run out of thruster fuel they are generally retired. The transponders and other onboard systems often outlive

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2272-461: The ISS and China 's Tiangong Space Station (TSS), which have been occupied since October 2000 with Expedition 1 and since June 2022 with Shenzhou 14 . The highest number of people at the same time on one space station has been 13, first achieved with the eleven day docking to the ISS of the 127th Space Shuttle mission in 2009. The record for most people on all space stations at the same time has been 17, first on May 30, 2023, with 11 people on

2343-467: The ISS and 6 on the TSS. Space stations are most often modular , featuring docking ports , through which they are built and maintained, allowing the joining or movement of modules and the docking of other spacecrafts for the exchange of people, supplies and tools. While space stations generally do not leave their orbit, they do feature thrusters for station keeping . The first mention of anything resembling

2414-577: The ISS on the SpaceX CRS-8 resupply mission. This module, based on NASA research in the 1990s, weighs 1,400 kilograms (3,100 lb) and was transported while compressed before being attached to the ISS by the space station arm and inflated to provide a 16 cubic metres (21 cu yd) volume. Whilst it was initially designed for a 2   year lifetime it was still attached and being used for storage in August 2022. The space station environment presents

2485-437: The ISS, orbiting today. Each crew member stays aboard the station for weeks or months but rarely more than a year. Early stations were monolithic designs that were constructed and launched in one piece, generally containing all their supplies and experimental equipment. A crew would then be launched to join the station and perform research. After the supplies had been consumed, the station was abandoned. The first space station

2556-617: The SES-5 satellite. SES-5 that was launched on 9 July 2012, at 18:38:30 UTC from Baikonur Cosmodrome , Site 81/24 and is now co-located with Astra 4A ( Sirius 4 ) at 5° East. This satellite provides a similar European and African coverage as Astra 4A . Geostationary orbit A geostationary orbit , also referred to as a geosynchronous equatorial orbit ( GEO ), is a circular geosynchronous orbit 35,786 km (22,236 mi) in altitude above Earth's equator , 42,164 km (26,199 mi) in radius from Earth's center, and following

2627-813: The South Pacific Ocean. The Tiangong Space Station ( Chinese : 天宫 ; pinyin : Tiāngōng ; lit. 'Heavenly Palace'), the first module of which was launched on 29 April 2021, is in low Earth orbit, 340 to 450 kilometres above the Earth at an orbital inclination of 42° to 43°. Its planned construction via 11 total launches across 2021–2022 was intended to extend the core module with two laboratory modules, capable of hosting up to six crew. These space stations have been announced by their host entity and are currently in planning, development or production. The launch date listed here may change as more information becomes available. (~23,548 cu ft) (~15892 cu ft) While originally Lockheed Martin

2698-400: The absence of servicing missions from the Earth or a renewable propulsion method, the consumption of thruster propellant for station-keeping places a limitation on the lifetime of the satellite. Hall-effect thrusters , which are currently in use, have the potential to prolong the service life of a satellite by providing high-efficiency electric propulsion . For circular orbits around a body,

2769-575: The assembly of space stations prior to the launch of crew. The Russian "second-generation" modules are able to be reconfigured to suit changing needs. As of 2009, RKK Energia was considering the removal and reuse of some modules of the ROS on the Orbital Piloted Assembly and Experiment Complex after the end of mission is reached for the ISS. However, in September 2017, the head of Roscosmos said that

2840-458: The concept was seen as impractical, so Hughes often withheld funds and support. By 1961, Rosen and his team had produced a cylindrical prototype with a diameter of 76 centimetres (30 in), height of 38 centimetres (15 in), weighing 11.3 kilograms (25 lb), light and small enough to be placed into orbit. It was spin stabilised with a dipole antenna producing a pancake shaped beam. In August 1961, they were contracted to begin building

2911-531: The connection in his introduction to The Complete Venus Equilateral . The orbit, which Clarke first described as useful for broadcast and relay communications satellites, is sometimes called the Clarke orbit. Similarly, the collection of artificial satellites in this orbit is known as the Clarke Belt. In technical terminology the orbit is referred to as either a geostationary or geosynchronous equatorial orbit, with

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2982-550: The crewed Shenzhou 10 in 2013. According to the China Manned Space Engineering Office , Tiangong-1 reentered over the South Pacific Ocean , northwest of Tahiti , on 2 April 2018 at 00:15 UTC. A second space laboratory Tiangong-2 was launched in September 2016, while a plan for Tiangong-3 was merged with Tiangong-2. The station made a controlled reentry on 19 July 2019 and burned up over

3053-496: The differential viability of the microbial cells, as a function of phylogenetic lineage, remain elusive. Like uncrewed spacecraft close to the Sun, space stations in the inner Solar System generally rely on solar panels to obtain power. Space station air and water is brought up in spacecraft from Earth before being recycled. Supplemental oxygen can be supplied by a solid fuel oxygen generator . The last military-use space station

3124-659: The equator and appear lower in the sky to an observer nearer the poles. As the observer's latitude increases, communication becomes more difficult due to factors such as atmospheric refraction , Earth's thermal emission , line-of-sight obstructions, and signal reflections from the ground or nearby structures. At latitudes above about 81°, geostationary satellites are below the horizon and cannot be seen at all. Because of this, some Russian communication satellites have used elliptical Molniya and Tundra orbits, which have excellent visibility at high latitudes. A worldwide network of operational geostationary meteorological satellites

3195-474: The equilibrium points would (without any action) be slowly accelerated towards the stable equilibrium position, causing a periodic longitude variation. The correction of this effect requires station-keeping maneuvers with a maximal delta-v of about 2 m/s per year, depending on the desired longitude. Solar wind and radiation pressure also exert small forces on satellites: over time, these cause them to slowly drift away from their prescribed orbits. In

3266-471: The first ever internal transfer of astronauts between two docked spaceships. In 1971, the Soviet Union developed and launched the world's first space station, Salyut 1 . The Almaz and Salyut series were eventually joined by Skylab , Mir , and Tiangong-1 and Tiangong-2 . The hardware developed during the initial Soviet efforts remains in use, with evolved variants comprising a considerable part of

3337-521: The first orbit on April 12, 1961, with Vostok 1 . The Apollo program had in its early planning instead of a lunar landing a crewed lunar orbital flight and an orbital laboratory station in orbit of Earth, at times called Project Olympus , as two different possible program goals, until the Kennedy administration sped ahead and made the Apollo program focus on what was originally planned to come after it,

3408-542: The following properties: An inclination of zero ensures that the orbit remains over the equator at all times, making it stationary with respect to latitude from the point of view of a ground observer (and in the Earth-centered Earth-fixed reference frame). The orbital period is equal to exactly one sidereal day. This means that the satellite will return to the same point above the Earth's surface every (sidereal) day, regardless of other orbital properties. For

3479-450: The following spacecraft. The Mir space station was in orbit from 1986 to 2001 and was supported and visited by the following spacecraft: Research conducted on the Mir included the first long term space based ESA research project EUROMIR   95 which lasted 179   days and included 35 scientific experiments. During the first 20 years of operation of the International Space Station, there were around 3,000 scientific experiments in

3550-775: The forward port of Harmony , requiring relocation of the PMA-2 . Axiom Space plans to attach up to two additional modules to its first core module, and send private astronauts to inhabit the modules. The modules would later detach into the Axiom Station in a manner similar to Russia's proposed OPSEK. China's first space laboratory, Tiangong-1 was launched in September 2011. The uncrewed Shenzhou 8 then successfully performed an automatic rendezvous and docking in November 2011. The crewed Shenzhou 9 then docked with Tiangong-1 in June 2012, followed by

3621-523: The ground. All geostationary satellites have to be located on this ring. A combination of lunar gravity, solar gravity, and the flattening of the Earth at its poles causes a precession motion of the orbital plane of any geostationary object, with an orbital period of about 53 years and an initial inclination gradient of about 0.85° per year, achieving a maximal inclination of 15° after 26.5 years. To correct for this perturbation , regular orbital stationkeeping maneuvers are necessary, amounting to

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3692-449: The lunar landing. The Project Olympus space station, or orbiting laboratory of the Apollo program, was proposed as an in-space unfolded structure with the Apollo command and service module docking. While never realized, the Apollo command and service module would perform docking maneuvers and eventually become a lunar orbiting module which was used for station-like purposes. But before that

3763-403: The new stations allowed Progress supply vehicles to be docked to the station, meaning that fresh supplies could be brought to aid long-duration missions. This concept was expanded on Salyut 7, which "hard docked" with a TKS tug shortly before it was abandoned; this served as a proof of concept for the use of modular space stations. The later Salyuts may reasonably be seen as a transition between

3834-578: The only continuous presence of humans in space . The first space station was Salyut 1 (1971), hosting the first crew, of the ill-fated Soyuz 11 . Consecutively space stations have been operated since Skylab (1973) and occupied since 1987 with the Salyut successor Mir . Uninterrupted occupation has been sustained since the operational transition from the Mir to the International Space Station (ISS), with its first occupation in 2000. Currently there are two fully operational space stations –

3905-476: The planet now have terrestrial communications facilities ( microwave , fiber-optic ), with telephone access covering 96% of the population and internet access 90%, some rural and remote areas in developed countries are still reliant on satellite communications. Most commercial communications satellites , broadcast satellites and SBAS satellites operate in geostationary orbits. Geostationary communication satellites are useful because they are visible from

3976-623: The real satellite. They lost Syncom 1 to electronics failure, but Syncom 2 was successfully placed into a geosynchronous orbit in 1963. Although its inclined orbit still required moving antennas, it was able to relay TV transmissions, and allowed for US President John F. Kennedy in Washington D.C., to phone Nigerian prime minister Abubakar Tafawa Balewa aboard the USNS Kingsport docked in Lagos on August 23, 1963. The first satellite placed in

4047-524: The same plane, altitude and speed; however, the presence of satellites in eccentric orbits allows for collisions at up to 4 km/s. Although a collision is comparatively unlikely, GEO satellites have a limited ability to avoid any debris. At geosynchronous altitude, objects less than 10 cm in diameter cannot be seen from the Earth, making it difficult to assess their prevalence. Despite efforts to reduce risk, spacecraft collisions have occurred. The European Space Agency telecom satellite Olympus-1

4118-405: The sky. A geostationary orbit can be achieved only at an altitude very close to 35,786 kilometres (22,236 miles) and directly above the equator. This equates to an orbital speed of 3.07 kilometres per second (1.91 miles per second) and an orbital period of 1,436 minutes, one sidereal day . This ensures that the satellite will match the Earth's rotational period and has a stationary footprint on

4189-533: The sun and cold temperatures for long periods of time. They are typically made from stainless steel , titanium and high-quality aluminum alloys , with layers of insulation such as Kevlar as a ballistics shield protection. The International Space Station (ISS) has a single inflatable module, the Bigelow Expandable Activity Module , which was installed in April   2016 after being delivered to

4260-576: The technical feasibility of separating the station to form OPSEK had been studied, and there were now no plans to separate the Russian segment from the ISS. In contrast, the main US modules launched on the Space Shuttle and were attached to the ISS by crews during EVAs . Connections for electrical power, data, propulsion, and cooling fluids are also made at this time, resulting in an integrated block of modules that

4331-444: The terms used somewhat interchangeably. The first geostationary satellite was designed by Harold Rosen while he was working at Hughes Aircraft in 1959. Inspired by Sputnik 1 , he wanted to use a geostationary satellite to globalise communications. Telecommunications between the US and Europe was then possible between just 136 people at a time, and reliant on high frequency radios and an undersea cable . Conventional wisdom at

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4402-485: The thruster fuel and by allowing the satellite to move naturally into an inclined geosynchronous orbit some satellites can remain in use, or else be elevated to a graveyard orbit . This process is becoming increasingly regulated and satellites must have a 90% chance of moving over 200 km above the geostationary belt at end of life. Space debris at geostationary orbits typically has a lower collision speed than at low Earth orbit (LEO) since all GEO satellites orbit in

4473-501: The time was that it would require too much rocket power to place a satellite in a geostationary orbit and it would not survive long enough to justify the expense, so early efforts were put towards constellations of satellites in low or medium Earth orbit. The first of these were the passive Echo balloon satellites in 1960, followed by Telstar 1 in 1962. Although these projects had difficulties with signal strength and tracking, issues that could be solved using geostationary orbits,

4544-515: The two groups. Unlike previous stations, the Soviet space station Mir had a modular design ; a core unit was launched, and additional modules, generally with a specific role, were later added. This method allows for greater flexibility in operation, as well as removing the need for a single immensely powerful launch vehicle . Modular stations are also designed from the outset to have their supplies provided by logistical support craft, which allows for

4615-606: The weeks or months that current missions typically last. Possible solutions include the creation of artificial gravity by a rotating structure , the inclusion of radiation shielding , and the development of on-site agricultural ecosystems. Some designs might even accommodate large numbers of people, becoming essentially "cities in space" where people would reside semi-permanently. Molds that develop aboard space stations can produce acids that degrade metal, glass, and rubber. Despite an expanding array of molecular approaches for detecting microorganisms, rapid and robust means of assessing

4686-402: Was Salyut 1 , which was launched by the Soviet Union on April 19, 1971. The early Soviet stations were all designated "Salyut", but among these, there were two distinct types: civilian and military. The military stations, Salyut 2 , Salyut 3 , and Salyut 5 , were also known as Almaz stations. The civilian stations Salyut 6 and Salyut 7 were built with two docking ports, which allowed

4757-624: Was included in the project, as of 2024, it appears their primary role has been filled by Airbus , to provide the main habitat for the station. As of 2024, they are no longer listed as a partner on Starlab's website. (14,126 cu ft) (29,000 cu ft) Two types of space stations have been flown: monolithic and modular. Monolithic stations consist of a single vehicle and are launched by one rocket. Modular stations consist of two or more separate vehicles that are launched independently and docked on orbit. Modular stations are currently preferred due to lower costs and greater flexibility. A space station

4828-494: Was launched in 1963. Communications satellites are often placed in a geostationary orbit so that Earth-based satellite antennas do not have to rotate to track them but can be pointed permanently at the position in the sky where the satellites are located. Weather satellites are also placed in this orbit for real-time monitoring and data collection, and navigation satellites to provide a known calibration point and enhance GPS accuracy. Geostationary satellites are launched via

4899-451: Was renamed SES Astra (a subsidiary of SES) and the satellite renamed Astra 4B. In 2011, SES Astra was merged back into SES and the satellite renamed SES-5. It was constructed by Space Systems/Loral , and is based on the SSL 1300 satellite bus . It carries 24 C-band and 36 Ku-band transponders . It covers Atlantic Ocean , Sub-Saharan Africa , North Africa , Europe, Middle East . SES 5

4970-490: Was struck by a meteoroid on August 11, 1993, and eventually moved to a graveyard orbit , and in 2006 the Russian Express-AM11 communications satellite was struck by an unknown object and rendered inoperable, although its engineers had enough contact time with the satellite to send it into a graveyard orbit. In 2017, both AMC-9 and Telkom-1 broke apart from an unknown cause. A typical geostationary orbit has

5041-695: Was the Soviet Salyut 5 , which was launched under the Almaz program and orbited between 1976 and 1977. Space stations have harboured so far the only long-duration direct human presence in space. After the first station, Salyut 1 (1971), and its tragic Soyuz 11 crew, space stations have been operated consecutively since Skylab (1973–1974), having allowed a progression of long-duration direct human presence in space. Long-duration resident crews have been joined by visiting crews since 1977 ( Salyut 6 ), and stations have been occupied by consecutive crews since 1987 with

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