international space station (page 5)

Launch and docking windows

Prior to a ship's docking to the ISS, navigation and attitude control (GNC) is handed over to the ground control of the ships' country of origin. GNC is set to allow the station to drift in space, rather than fire its thrusters or turn using gyroscopes. The solar panels of the station are turned edge-on to the incoming ships, so residue from its thrusters does not damage the cells. When a NASA shuttle docked to the station, other ships were grounded, as the carbon wingtips, cameras, windows, and instruments aboard the shuttle were at too much risk from damage from thruster residue from other ships movements.

Approximately 30% of NASA shuttle launch delays were caused by poor weather. Occasional priority was given to the Soyuz arrivals at the station where the Soyuz carried crew with time-critical cargoes such as biological experiment materials, also causing shuttle delays. Departure of the NASA shuttle was often delayed or prioritised according to weather over its two landing sites. Whilst the Soyuz is capable of landing anywhere, anytime, its planned landing time and place is chosen to give consideration to helicopter pilots and ground recovery crew, to give acceptable flying weather and lighting conditions. Soyuz launches occur in adverse weather conditions, however the cosmodrome had been shut down on occasions when buried by snow drifts up to 6 metres in depth, hampering ground operations.

Sightings

Naked eye

The ISS is visible to the naked eye before sunrise or after sunset as a slow-moving, bright white dot, crossing the sky in 2 to 5 minutes. This happens before dawn and after dusk when the ISS is sunlit but the ground and sky are dark, which is typically the case up to a few hours after sunset or before sunrise.^[248] Because of the size of its reflective surface area, the ISS is the brightest man made object in the sky excluding flares, with an approximate maximum magnitude of −4 when overhead, similar to Venus. The ISS, like many satellites including the Iridium constellation, can also produce flares as sunlight glints off reflective surfaces as it orbits of up to 8 or 16 times the brightness of Venus.^[249][250] The ISS is also visible during broad daylight conditions, albeit with a great deal more effort.

Tools are provided by a number of websites such as Heavens-Above as well as smartphone applications that use the known orbital data and the observer's longitude and latitude to predict when the ISS will be visible (weather permitting), where the station will appear to rise to the observer, the altitude above the horizon it will reach and the duration of the pass before the station disappears to the observer either by setting below the horizon or entering into Earth's shadow.^{[251][252][253][254]}

In November 2012 NASA launched its 'Spot the Station' service, which sends people text and email alerts when the station is due to fly above their town.^[255]

The ISS and HTV photographed using a telescope-mounted camera by Ralf Vandebergh		A time exposure of a station pass

The station is visible from 95% of the inhabited land on Earth, but is not visible from extreme northern or southern latitudes.^[205] OPSEK will orbit at a higher inclination of 71 degrees, allowing observation to and from all of the Russian federation.

Astrophotography

Using a telescope mounted camera to photograph the station is a popular hobby for astronomers, ^[256] whilst using a mounted camera to photograph the Earth and stars is a popular hobby for crew.^[257] The use of a telescope or binoculars allows viewing of the ISS during daylight hours.^[258]

Parisian engineer and astrophotographer Thierry Legault, known for his photos of spaceships crossing the sun (called occultation), travelled to Oman in 2011, to photograph the sun, moon and space station all lined up.^[259] Legault, who received the Marius Jacquemetton award from the Société astronomique de France in 1999, and other hobbyists, use websites that predict when the ISS will pass in front of the Sun or Moon and what location those passes will be visible from.

Crew health and safety

Radiation

The ISS is partially protected from the space environment by the Earth's magnetic field. From an average distance of about 70,000 km, depending on Solar activity, the magnetosphere begins to deflect solar wind around the Earth and ISS. However, solar flares are still a hazard to the crew, who may receive only a few minutes warning. The crew of Expedition 10 took shelter as a precaution in 2005 in a more heavily shielded part of the ROS designed for this purpose during the initial 'proton storm' of an X-3 class solar flare,^[260][261] but without the limited protection of the Earth's magnetosphere, interplanetary manned missions are especially vulnerable.

 

Video of the Aurora Australis taken by the crew of Expedition 28 on an ascending pass from south of Madagascar to just north of Australia over the Indian Ocean.

Subatomic charged particles, primarily protons from cosmic rays and solar wind, are normally absorbed by the earth's atmosphere. When they interact in sufficient quantity, their effect becomes visible to the naked eye in a phenomenon called an aurora. Without the protection of the Earth's atmosphere, which absorbs this radiation, crews are exposed to about 1 millisievert each day, which is about the same as someone would get in a year on Earth from natural sources. This results in a higher risk of astronauts developing cancer. Radiation can penetrate living tissue, damage DNA, and cause damage to the chromosomes of lymphocytes. These cells are central to the immune system, and so any damage to them could contribute to the lowered immunity experienced by astronauts. Radiation has also been linked to a higher incidence of cataracts in astronauts. Protective shielding and protective drugs may lower the risks to an acceptable level.^[42]

The radiation levels experienced on the ISS are about five times greater than those experienced by airline passengers and crew. The Earth's electromagnetic field provides almost the same level of protection against solar and other radiation in low Earth orbit as in the stratosphere. Airline passengers, however, experience this level of radiation for no more than 15 hours for the longest intercontinental flights. For example, on a 12 hour flight an airline passenger would experience 0.1 millisieverts of radiation, or a rate of 0.2 millisieverts per day; only 1/5 the rate experienced by an astronaut in LEO.^[262]

Stress

There has been considerable evidence that psychosocial stressors are among the most important impediments to optimal crew morale and performance.^[263] Cosmonaut Valery Ryumin, twice Hero of the Soviet Union, wrote in his journal during a particularly difficult period onboard the Salyut 6 space station: “All the conditions necessary for murder are met if you shut two men in a cabin measuring 18 feet by 20 and leave them together for two months.”

NASA's interest in psychological stress caused by space travel, initially studied when their manned missions began, was rekindled when astronauts joined cosmonauts on the Russian space station Mir. Common sources of stress in early American missions included maintaining high performance while under public scrutiny, as well as isolation from peers and family. The latter is still often a cause of stress on the ISS, such as when NASA Astronaut Daniel Tani's mother died in a car accident, and when Michael Fincke was forced to miss the birth of his second child.

A study of the longest spaceflight concluded that the first three weeks represent a critical period where attention is adversely affected because of the demand to adjust to the extreme change of environment.^[264] While Skylab's 3 crews remained one, two, and three months respectively, long term crews on Salyut 6, Salyut 7, and the ISS last about five to six months while MIR's expeditions often lasted longer. The ISS working environment includes further stress caused by living and working in cramped conditions with people from very different cultures who speak a different language. First generation space stations had crews who spoke a single language, while second and third-generation stations have crew from many cultures who speak many languages. The ISS is unique because visitors are not classed automatically into 'host' or 'guest' categories as with previous stations and spacecraft, and may not suffer from feelings of isolation in the same way. Crew members with a military pilot background and those with an academic science background or teachers and politicians may have problems understanding each other’s jargon and worldview.

Medical

Astronaut Frank De Winne is attached to the TVIS treadmill with bungee cords aboard the International Space Station

Medical effects of long-term weightlessness include muscle atrophy, deterioration of the skeleton (osteopenia), fluid redistribution, a slowing of the cardiovascular system, decreased production of red blood cells, balance disorders, and a weakening of the immune system. Lesser symptoms include loss of body mass, and puffiness of the face.^[42]

Sleep is disturbed on the ISS regularly due to mission demands, such as incoming or departing ships. Sound levels in the station are unavoidably high; because the atmosphere is unable to thermosyphon, fans are required at all times to allow processing of the atmosphere which would stagnate in the freefall (zero-g) environment.

To prevent some of these adverse physiological effects, the station is equipped with two treadmills (including the COLBERT), and the aRED (advanced Resistive Exercise Device) which enables various weightlifting exercises which add muscle but do nothing for bone density,^[265] and a stationary bicycle; each astronaut spends at least two hours per day exercising on the equipment.^[162][163] Astronauts use bungee cords to strap themselves to the treadmill.^[266][267]

Orbital debris

A 7 gram object (shown in centre) shot at 7 km/s (23,000 ft/sec) (the orbital velocity of the ISS) made this 15 cm (5 7/8 in) crater in a solid block of aluminium.		Radar-trackable objects including debris, with distinct ring of geostationary satellites

At the low altitudes at which the ISS orbits there are a variety of space debris,^[268] consisting of many different objects including entire spent rocket stages, defunct satellites, explosion fragments—including materials from anti-satellite weapon tests, paint flakes, slag from solid rocket motors, and coolant released by US-A nuclear-powered satellites. These objects, in addition to natural micrometeoroids,^[269] are a significant threat. Large objects could destroy the station, but are less of a threat as their orbits can be predicted.^[270][271] Objects too small to be detected by optical and radar instruments, from approximately 1 cm down to microscopic size, number in the trillions. Despite their small size, some of these objects are still a threat because of their kinetic energy and direction in relation to the station. Spacesuits of spacewalking crew could puncture, causing exposure to vacuum.^[272]

The station's shields and structure are divided between the ROS and the USOS, with completely different designs. On the USOS, a thin aluminium sheet is held apart from the hull, the sheet causes objects to shatter into a cloud before hitting the hull thereby spreading the energy of the impact. On the ROS, a carbon plastic honeycomb screen is spaced from the hull, an aluminium honeycomb screen is spaced from that, with a screen-vacuum thermal insulation covering, and glass cloth over the top. It is about 50% less likely to be punctured, and crew move to the ROS when the station is under threat. Punctures on the ROS would be contained within the panels which are 70 cm square.

Example of risk management: A NASA model showing areas at high risk from impact for the International Space Station.

Space debris objects are tracked remotely from the ground, and the station crew can be notified.^[273] This allows for a Debris Avoidance Manoeuvre (DAM) to be conducted, which uses thrusters on the Russian Orbital Segment to alter the station's orbital altitude, avoiding the debris. DAMs are not uncommon, taking place if computational models show the debris will approach within a certain threat distance. Eight DAMs had been performed prior to March 2009,^[274] the first seven between October 1999 and May 2003.^[275] Usually the orbit is raised by one or two kilometres by means of an increase in orbital velocity of the order of 1 m/s. Unusually there was a lowering of 1.7 km on 27 August 2008, the first such lowering for 8 years.^[275][276] There were two DAMs in 2009, on 22 March and 17 July.^[277] If a threat from orbital debris is identified too late for a DAM to be safely conducted, the station crew close all the hatches aboard the station and retreat into their Soyuz spacecraft, so that they would be able to evacuate in the event the station was seriously damaged by the debris. This partial station evacuation has occurred on 13 March 2009, 28 June 2011 and 24 March 2012.^[278] Ballistic panels, also called micrometeorite shielding, are incorporated into the station to protect pressurised sections and critical systems. The type and thickness of these panels varies depending upon their predicted exposure to damage.

Politics

International co-operation

Primary contributing nations   Formerly contracted nations		Allocation of US Orbital Segment hardware usage between contributors

International co-operation in space began between the United States and the Soviet Union in 1972, with the Apollo-Soyuz Test Project. This cooperative venture resulted in the July 1975 docking of Soyuz 19 with an Apollo spacecraft. From 1978–1987 the USSR's Interkosmos programme included allied Warsaw Pact countries, and countries which were not Soviet allies, such as India, Syria and France, in manned and unmanned missions to Space stations Salyut 6 and 7. In 1986 the USSR extended this co-operation to a dozen countries in the Mir programme. In 1994–98 NASA Space Shuttles and crew visited MIR in the Shuttle-Mir programme. In 1998 the ISS programme began.^{[citation needed]}

In March 2012, a meeting in Quebec City between the leaders of the Canadian Space Agency and those from Japan, Russia, the United States and involved European nations resulted in a renewed pledge to maintain the International Space Station until at least 2020. NASA reports to be still committed to the principles of the mission but also to use the station in new ways, which were not elaborated. CSA President Steve MacLean stated his belief that the station's Canadarm will continue to function properly until 2028, alluding to Canada's likely extension of its involvement beyond 2020.^[279]

Ownership of modules, station usage by participant nations, and responsibilities for station resupply are established by the Space Station Intergovernmental Agreement (IGA). This international treaty was signed on 28 January 1998 by the United States of America, Russia, Japan, Canada and eleven member states of the European Space Agency (Belgium, Denmark, France, Germany, Italy, The Netherlands, Norway, Spain, Sweden, Switzerland, and the United Kingdom).^[17][18] With the exception of the United Kingdom, all of the signatories went on to contribute to the Space Station project. A second layer of agreements was then achieved, called Memoranda of Understanding (MOU), between NASA and ESA, CSA, RKA and JAXA. These agreements are then further split, such as for the contractual obligations between nations, and trading of partners' rights and obligations.^[18] Use of the Russian Orbital Segment is also negotiated at this level.^[23]

Annotated image of the Russian Orbital Segment configuration as of 2011		The USOS is shared by NASA, ESA, CSA and JAXA

In addition to these main intergovernmental agreements, Brazil originally joined the programme as a bilateral partner of the United States by a contract with NASA to supply hardware.^[280] In return, NASA would provide Brazil with access to its ISS facilities on-orbit, as well as a flight opportunity for one Brazilian astronaut during the course of the ISS programme. However, due to cost issues, the subcontractor Embraer was unable to provide the promised ExPrESS pallet, and Brazil left the programme.^[281] Italy has a similar contract with NASA to provide comparable services, although Italy also takes part in the programme directly via its membership in ESA.^[282] Expanding the partnership would require unanimous agreement of the existing partners. Chinese participation has been prevented by unilateral US opposition.^[283][284] The heads of both the South Korean and Indian space agency ISRO announced at the first plenary session of the 2009 International Astronautical Congress that their nations wished to join the ISS programme, with talks due to begin in 2010. The heads of agency also expressed support for extending ISS lifetime.^[285] European countries not part of the programme will be allowed access to the station in a three-year trial period, ESA officials say.^[286]

The Russian part of the station is operated and controlled by the Russian Federation's space agency and provides Russia with the right to nearly one-half of the crew time for the ISS. The allocation of remaining crew time (three to four crew members of the total permanent crew of six) and hardware within the other sections of the station is as follows: Columbus: 51% for the ESA, 46.7% for NASA, and 2.3% for CSA.^[18] Kibō: 51% for the JAXA, 46.7% for NASA, and 2.3% for CSA.^[180] Destiny: 97.7% for NASA and 2.3% for CSA.^[287] Crew time, electrical power and rights to purchase supporting services (such as data upload and download and communications) are divided 76.6% for NASA, 12.8% for JAXA, 8.3% for ESA, and 2.3% for CSA.^{[18][102][176][180][287]}

China

China is not an ISS partner, and no Chinese nationals have been aboard. China has its own contemporary manned space programme, Project 921, and has carried out cooperation and exchanges with countries such as Russia and Germany in manned and unmanned space projects.^[288][289] China launched its first experimental space station,^[290] Tiangong 1, in September 2011,^[291] and has officially initiated the permanently manned Chinese space station project.^[292]

In 2007, Chinese vice minister of science and technology Li Xueyong said that China would like to participate in the ISS.^[293] In 2010, ESA Director-General Jean-Jacques Dordain stated his agency was ready to propose to the other 4 partners that China be invited to join the partnership, but that this needs to be a collective decision by all the current partners.^[52] While ESA is open to China's inclusion, the US is against it. US concerns over the transfer of technology that could be used for military purposes echo similar concerns over Russia's participation prior to its membership.^[294] Concerns over Russian involvement were overcome and NASA became solely dependent upon Russian crew capsules when its Shuttles were grounded after the Columbia accident in 2003,^[295] and again after its retirement in 2011.^[296][297] China believes that international exchanges and cooperation in the field of aerospace engineering should be intensified on the basis of mutual benefit, peaceful use and common development.^[288] China's manned Shenzhou spacecraft use an APAS docking system, developed after a 1994–95 deal for the transfer of Russian Soyuz spacecraft technology. Included in the agreement was training, provision of Soyuz capsules, life support systems, docking systems, and space suits. American observers comment that Shenzhou spacecraft could dock at the ISS if it became politically feasible, whilst Chinese engineers say work would still be required on the rendezvous system. Shenzhou 7 passed within about 50 kilometres of the ISS.^{[289][298][299]}

American co-operation with China in space is limited, though efforts have been made by both sides to improve relations,^[300] but in 2011 new American legislation further strengthened legal barriers to co-operation, preventing NASA co-operation with China or Chinese owned companies, even the expenditure of funds used to host Chinese visitors at NASA facilities, unless specifically authorised by new laws,^[54] at the same time China, Europe and Russia have a co-operative relationship in several space exploration projects.^[301] Between 2007 and 2011, the space agencies of Europe, Russia and China carried out the ground-based preparations in the Mars500 project, which complement the ISS-based preparations for a manned mission to Mars.^[302]

End of mission

Many ISS resupply spacecraft have already undergone atmospheric re-entry, such as Jules Verne ATV

According to a 2009 report, Space Corporation Energia is considering methods to remove from the station some modules of the Russian Orbital Segment when the end of mission is reached and use them as a basis for a new station, known as the Orbital Piloted Assembly and Experiment Complex (OPSEK). The modules under consideration for removal from the current ISS include the Multipurpose Laboratory Module (MLM), currently scheduled to be launched in 2014, with other Russian modules which are currently planned to be attached to the MLM until 2015. Neither the MLM nor any additional modules attached to it would have reached the end of their useful lives in 2016 or 2020. The report presents a statement from an unnamed Russian engineer who believes that, based on the experience from Mir, a thirty-year life should be possible, except for micrometeorite damage, because the Russian modules have been built with on-orbit refurbishment in mind.^[303]

According to the Outer Space Treaty the United States and Russia are legally responsible for all modules they have launched.^[304] In ISS planning, NASA examined options including returning the station to Earth via shuttle missions (deemed too expensive, as the station (USOS) is not designed for disassembly and this would require at least 27 shuttle missions^[305]), natural orbital decay with random reentry similar to Skylab, boosting the station to a higher altitude (which would simply delay reentry) and a controlled targeted de-orbit to a remote ocean area.^[306]

The technical feasibility of a controlled targeted deorbit into a remote ocean was found to be possible only with Russia's assistance.^[306] The Russian Space Agency has experience from de-orbiting the Salyut 4, 5, 6, 7 and Mir space stations, while NASA's first intentional controlled de-orbit of a satellite (the Compton Gamma Ray Observatory) occurred in 2000.^[307] As of late 2010, the preferred plan is to use a slightly modified Progress spacecraft to de-orbit the ISS.^[308] This plan was seen as the simplest, most cost efficient one with the highest margin.^[308] Skylab, the only space station built and launched entirely by the US, decayed from orbit slowly over 5 years, and no attempt was made to de-orbit the station using a deorbital burn. Remains of Skylab hit populated areas of Esperance, Western Australia^[309] without injuries or loss of life.

The Exploration Gateway Platform, a discussion by NASA and Boeing at the end of 2011, suggested using leftover USOS hardware and 'Zvezda 2' [sic] as a refueling depot and servicing station located at one of the Earth Moon Lagrange points, L1 or L2. While the entire USOS cannot be reused and will be discarded, some other Russian modules are planned to be reused. Nauka, the Node module, two science power platforms and Rassvet, launched between 2010 and 2015 and joined to the ROS may be separated to form OPSEK.^[310] The Nauka module of the ISS will be used in the station, whose main goal is supporting manned deep space exploration. OPSEK will orbit at a higher inclination of 71 degrees, allowing observation to and from all of the Russian Federation.

Programme cost

As of 2010 NASA budgeted $58.7 billion for the station from 1985 to 2015, or $72.4 billion dollars in 2010. The cost is $150 billion including 36 shuttle flights at $1.4 billion each, Russia's $12 billion ISS budget, Europe's $5 billion, Japan's $5 billion, and Canada's $2 billion. Assuming 20,000 person-days of use from 2000 to 2015 by two to six-person crews, each person-day would cost $7.5 million, less than half the inflation adjusted $19.6 million ($5.5 million before inflation) per person-day of Skylab.^[311]

Notes