International Space Station

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International Space Station

The International Space Station as seen from the departing Space Shuttle Discovery on STS-124.
ISS Insignia
Station statistics
NSSDC ID:	1998-067A
Call sign:	Alpha (only by NASA)
Crew:	3
Launch:	1998-2011
Launch pad:	KSC LC-39, Baikonur LC-1/5 & 81/23
Mass:	300,214 kg (661,857 lb) (2008-06-18)
Length:	58.2 m (191 ft) along truss (2007-02-22)
Width:	44.5 m (146 ft) from Destiny to Zvezda 73.15 m (240 ft) span of solar arrays (2007-02-22)
Height:	27.4 m (90 ft) (2007-02-22)
Living volume:	358 m³ (12,626 ft³) (2008-06-18)
Atmospheric pressure:	1013 hPa (29.91 inHg)
Perigee:	350 km (189 nmi) (2008-10-22)
Apogee:	354 km (191 nmi) (2008-10-22)
Orbit inclination:	51.6419 degrees (2008-10-22)
Typical orbit altitude:	340.5 km (183.86 nmi)
Average speed:	27,743.8 km/h (17,239.2 mph, 7706.6 m/s)
Orbital period:	91.34 minutes
Orbits per day:	15.72397664 (2008-10-22)
Days in orbit:	3652 (19 November 2008)
Days occupied:	2941 (19 November 2008)
Number of orbits:	c.57636 (19 November 2008)
Distance travelled:	c.2,000,000,000 km (1,100,000,000 nmi)
Statistics as of November 20, 2007 (unless noted otherwise).
References: [1][2][3]
Configuration
International Space Station current elements
International Space Station

The International Space Station (ISS) is a research facility currently being assembled in outer space, the on-orbit construction of which began in 1998. The space station is in a Low Earth Orbit and can be seen from Earth with the naked eye; it orbits at an altitude of approximately 350 km (190 mi) above the surface of the Earth,^[4][5][6] and travels at an average speed of 27,700 kilometres (17,210 mi) per hour, completing 15.7 orbits per day.^[4]

The space station is a joint project among the space agencies of the United States (NASA), Russia (RKA), Japan (JAXA), Canada (CSA) and eleven European countries (ESA).^[7] The Brazilian Space Agency (AEB, Brazil) participates through a separate contract with NASA. The Italian Space Agency similarly has separate contracts for various activities not done in the framework of ESA's ISS works (where Italy also fully participates). China had reportedly expressed interest in the project,^[8] especially if China was able to work with the RKA,^[9] though it is not currently involved.^[8] To mark the level of cooperation that the project is fostering between nations, in 2001, the station received the Prince of Asturias Award for International Cooperation.^[10]

The ISS is a continuation of several other previously planned space stations; Russia's Mir 2, the US Space Station Freedom, the European Columbus laboratory and the Japanese Kibō laboratory. The projected completion date is 2011, with the station remaining in operation at least until 2016. As of 2008, the ISS is larger than any previous space station.

The ISS has been continuously staffed since the first resident crew, Expedition 1, entered the station on November 2, 2000, thereby providing a permanent human presence in space. The crew of Expedition 18 are currently aboard. At present the station has a capacity for a crew of three, however, in order to fulfil an active research program, beginning with Expedition 19, it will be staffed by a resident crew of six.^[11] Early crew members all came from the Russian and American space programs, until German ESA astronaut Thomas Reiter joined the Expedition 13 crew in July 2006, becoming the first crew member from another space agency. The station has, however, been visited by astronauts from 16 countries, and was the destination of the first five space tourists.

The station is serviced primarily by Russian Soyuz and Progress spacecraft and American Space Shuttle orbiters. On March 9, 2008, the European Space Agency (ESA) launched an Ariane 5 with the first Automated Transfer Vehicle, Jules Verne, toward the ISS carrying over 8,000 kilograms of cargo. Several other servicing vehicles are also in various stages of planning.

[edit] Origins

Please help improve this section by expanding it. Further information might be found on the talk page or at requests for expansion. (November 2008)

See also: Shuttle-Mir Program

In the early 1980s, NASA planned Space Station Freedom as a counterpart to the Soviet Salyut and Mir space stations. It never left the drawing board and with the end of the Soviet Union and the Cold War, it was nearly canceled by the US House of Representatives due to budgetary and design concerns. Similar problems for proposed space stations by other countries as well as the end of the space race prompted the US administration officials to start negotiations with international partners Europe, Russia, Japan and Canada in the early 1990s in order to build a truly international space station. This project was first announced in November 1993 and was called Space Station Alpha.^[12] It was planned to combine the proposed space stations of all participating space agencies: NASA's Space Station Freedom, Russia's Mir-2 (the successor to Mir, the core of which is now Zvezda) and ESA's Columbus that was planned to be a stand-alone spacelab.

[edit] Space station

[edit] Assembly

Main article: Assembly of the International Space Station

See also: ISS assembly sequence

The assembly of the International Space Station is a major aerospace engineering endeavour. When assembly is complete the ISS will have a pressurised volume of approximately 1,000 m³. Assembly began in November 1998, and as of July 2008 the station is approximately 85% complete.

The first segment of the ISS, the Zarya FGB, was launched into orbit in November 1998 on a Russian Proton rocket, and was followed two weeks later by the first of three 'node' modules, Unity, launched aboard STS-88. This bare 2-module core of the ISS remained unmanned for the next one and a half years, until in July 2000 the Russian module Zvezda was added, allowing a maximum crew of three astronauts or cosmonauts to be on the ISS permanently - the first resident crew, Expedition 1, was sent that November. 2000 also saw the arrival of two segments of the station's Integrated Truss Structure, the Z1 and P6 truss, together providing the embryonic station with communications, guidance, electrical grounding (on Z1) and power via a pair of solar array wings (on P6).

Over the next two years the station continued to expand, with a Soyuz rocket delivering the Pirs docking compartment and Space Shuttles Discovery, Atlantis and Endeavour between them carrying the Destiny laboratory and Quest airlock to orbit, in addition to the station's robot arm, Canadarm2, and several more segments of truss.

The ambitious expansion schedule was brought to an abrupt halt, however, following the destruction of the Space Shuttle Columbia on STS-107. The resulting hiatus in the Space Shuttle program led to a halt in station assembly until the launch of Discovery on STS-114 in 2005.

The official Return to Assembly was marked by the delivery by Atlantis, flying STS-115, of the station's second set of solar arrays, which were followed by several more truss segments and a third set of arrays on STS-116, STS-117 and STS-118. This major expansion of the station's power generating abilities meant that more pressurised modules could be accommodated, and as a result the Harmony node and Columbus European laboratory were added, followed shortly by the first two components of Kibō, the Japanese Experiment Module.

As of July 2008, the station consists of ten pressurised modules, in addition to all but one of the components of the Integrated Truss Structure. Awaiting launch are the station's final set of solar arrays (set for delivery on STS-119), the final section of Kibō, the American Node 3, and the European Robotic Arm, in addition to several Russian modules. Also awaiting launch is the Alpha Magnetic Spectrometer, recently manifested on what is currently the final Space Shuttle flight, STS-134. Assembly is expected to be completed by 2011, by which point the station will have a mass in excess of 400 tons.^[1][13]

[edit] Pressurised modules

The ISS is currently under construction, and will eventually consist of fourteen pressurised modules with a combined volume of around 1,000 m³. These modules include laboratories, docking compartments, airlocks, nodes and living quarters, nine of which are already in orbit, with the remaining five awaiting launch. Each module is launched either by Space Shuttle, Proton rocket or Soyuz rocket, and is listed below along with its purpose, launch date and mass.

Module	Assembly flight	Launch date	Launch vehicle	Nation	Mass	Isolated View	Station View
Zarya	1A/R	November 20, 1998	Proton-K	Russia (Builder) US (Financier)	19,323 kg (42,600 lb)
	Provided electrical power, storage, propulsion, and guidance during initial assembly, now serves as a storage module (both inside the pressurised section and in the externally mounted fuel tanks).
Unity (Node 1)	2A	December 4, 1998	Space Shuttle Endeavour, STS-88	US	11,612 kg (25,600 lb)
	First node module, connecting the American section of the station to the Russian section (via PMA-1). Provides berthing locations for the Z1 truss, Quest airlock, Destiny laboratory and Node 3.
Zvezda (Service Module)	1R	July 12, 2000	Proton-K	Russia	19,051 kg (42,000 lb)
	Station service module, providing main living quarters for resident crews, environmental systems and attitude & orbit control, in addition to docking locations for Soyuz spacecraft, Progress spacecraft and the Automated Transfer Vehicle. The addition of the module rendered the ISS permanently habitable for the first time.
Destiny (US Laboratory)	5A	February 7, 2001	Space Shuttle Atlantis, STS-98	US	14,515 kg (32,000 lb)
	Primary research facility for US payloads aboard the ISS, Destiny provides the station with generic laboratory capabilities, with capacity for 24 International Standard Payload Racks. The laboratory also provides various environmental systems and living quarters to the station, and is the module to which most of the Integrated Truss Structure is affixed.
Quest (Joint Airlock)	7A	July 12, 2001	Space Shuttle Atlantis, STS-104	US	6,064 kg (13,370 lb)
	Primary airlock for the ISS, hosting spacewalks with both US EMU and Russian Orlan spacesuits. Quest consists of two segments, the equipment lock that stores spacesuits and equipment, and the crew lock from which astronauts can exit into space.
Pirs (Docking Compartment)	4R	September 14, 2001	Soyuz-U	Russia	3,580 kg (7,900 lb)
	Provides the ISS with additional docking ports for Soyuz & Progress spacecraft, and allows egress and ingress for spacewalks by cosmonauts using Russian Orlan spacesuits, in addition to providing storage space for these spacesuits.
Harmony (Node 2)	10A	October 23, 2007	Space Shuttle Discovery, STS-120	Europe (Builder) US (Financier)	14,288 kg (31,500 lb)
	The second of the station's node modules, Harmony is the utility hub of the ISS. The module contains four racks that provide electrical power, bus electronic data, and acts as a central connecting point for several other components via its six Common Berthing Mechanisms (CBMs). The European Columbus and Japanese Kibō laboratories are permanently berthed to the module, and US Space Shuttles dock to the ISS via PMA-2, attached to Harmony's front port. In addition, the module serves as a berthing port for the Multi-Purpose Logistics Modules during logistics flights.
Columbus (European Laboratory)	1E	February 7, 2008[14]	Space Shuttle Atlantis, STS-122	Europe	12,800 kg (28,000 lb)
	Primary research facility for European payloads aboard the ISS, providing ten International Standard Payload Racks and mounting locations for external experiments, including the European Technology Exposure Facility, Solar Monitoring Observatory,Materials International Space Station Experiment and Atomic Clock Ensemble in Space.
Experiment Logistics Module (JEM-ELM)	1J/A	March 11, 2008	Space Shuttle Endeavour, STS-123	Japan	8,386 kg (18,490 lb)[15]
	Part of the Kibō Japanese Experiment Module laboratory, the ELM provides storage and transportation facilities to the laboratory, with a pressurised section to serve internal payloads and an unpressurised section to serve external payloads.
Japanese Pressurised Module (JEM-PM)	1J	May 31, 2008	Space Shuttle Discovery, STS-124	Japan	14,800 kg (33,000 lb)[16]
	Part of the Kibō Japanese Experiment Module laboratory, the PM is the core module of Kibō to which the ELM & Exposed Facility are berthed. The laboratory is the largest single ISS module, and contains ten International Standard Payload Racks.
Mini-Research Module 2	5R	c. August 2009	Soyuz-FG	Russia
	Not yet launched. The newest Russian component of the ISS, MRM2 will likely be used for docking and cargo storage aboard the station.
Node 3	20A	c. December 2009	Space Shuttle Endeavour, STS-130	Europe (Builder) US (Financier)	14,311 kg (31,550 lb)
	Not yet launched. The last of the station's US nodes, Node 3 will contain an advanced life support system to recycle waste water for crew use and generate oxygen for the crew to breathe. The node also provides four berthing locations for more attached pressurised modules or crew transportation vehicles, in addition to the permanent berthing location for the station's Cupola.
Cupola	20A	c. December 2009	Space Shuttle Endeavour, STS-130	Europe (Builder) US (Financier)	1,800 kg (4,000 lb)
	Not yet launched. The Cupola is an observatory module that will provide ISS crew members with a direct view of robotic operations and docked spacecraft, as well as an observation point for watching the Earth. The module will come equipped with robotic workstations for operating the SSRMS and shutters to prevent its windows from being damaged by micrometeorites.
Mini-Research Module 1	ULF4	c. April 2010	Space Shuttle Discovery, STS-132	Russia	4,700 kg (10,000 lb)
	Not yet launched. MRM1 will be used for docking and cargo storage aboard the station.
Multipurpose Laboratory Module	3R	c. December 2011[13]	Proton-M	Russia	21,300 kg (47,000 lb)
	Not yet launched. The MLM will be Russia's primary research module as part of the ISS, and will be used for experiments, docking and cargo logistics. It will also serve as a crew work and rest area, and will also be equipped with a backup attitude control system that can be used to control the station's attitude.

[edit] Power supply

Main article: Electrical system of the International Space Station

The source of electrical power for the ISS is the Sun: light is converted into electricity through the use of solar arrays. Before assembly flight 4A (shuttle mission STS-97, November 30, 2000) the only power source was the Russian solar panels attached to the Zarya and Zvezda modules: the Russian segment of the station uses 28 volts DC (as does the Shuttle). In the remainder of the station, electricity is provided by the solar arrays attached to the truss at a voltage ranging from 130 to 180 volts DC. The power is then stabilized and distributed at 160 volts DC, before finally being converted to the user-required 124 volts DC - this high-voltage distribution line allows for smaller power lines, reducing weight. Power can be shared between the two segments of the station using converters, and this feature is essential since the cancellation of the Russian Science Power Platform, as the Russian segment will depend on the US built solar arrays for power.^[17]

The solar array normally tracks the Sun to maximize the amount of solar power. The array is about 375 m² in area and 58 metres (190 ft) long. In the fully-complete configuration, the solar arrays track the sun in each orbit by rotating the alpha gimbal; while the beta gimbal adjusts for the angle of the sun from the orbital plane. (Until the main truss structure arrived, the arrays were in a temporary position perpendicular to the final orientation, and in this configuration, as shown in the image to the right, the beta gimbal was used for the main solar tracking.) Another tracking option, Night Glider mode, can be used to slightly reduce the effects of drag produced by the tenuous upper atmosphere through which the station flies by orienting the solar arrays edgewise to the velocity vector.

[edit] Attitude control

The attitude (orientation) of the station is maintained by either of two mechanisms. Normally, a system using several control moment gyroscopes (CMGs) keeps the station oriented, with Destiny forward of Unity, the P truss on the port side and Pirs on the earth-facing (nadir) side. When the CMG system becomes saturated (a situation whereby a CMG exceeds its operational range or cannot track a series of rapid movements, and stops working) it can lose its ability to control station attitude. In this event, the Russian attitude control system is designed to take over automatically, using thrusters to maintain station attitude and allowing the CMG system to desaturate, a situation which has occurred once, during Expedition 10.^[18] When a Space Shuttle is docked to the station, it can also be used to maintain station attitude. This procedure was used during STS-117 as the S3/S4 truss was being installed.

[edit] Altitude control

The ISS is maintained at an orbit from a minimum altitude limit of 278 km to a maximum limit of 460 km. The normal maximum limit is 425 km to allow Soyuz rendezvous missions. Because ISS is constantly losing altitude due to slight atmospheric drag and gravity gradient effects, it needs to be boosted to a higher altitude several times each year.^[19] These effects vary from day-to-day, however, due to changes in the density of the outer atmosphere due to solar activity.^[20] The boosting can be performed by two boosters on the Zvezda module, a docked Space Shuttle, a Progress resupply vessel or by ESA's ATV and takes approximately two orbits (three hours) in which it is boosted several kilometers higher.^[19] While it is being built the altitude is relatively low so that it is easier to fly the space shuttle — with its large payloads — to the station. When the station is complete, it will be raised to a higher (and, therefore, more stable) orbit to reduce the need for reboosts to take place.^[21]

[edit] Microgravity

At the station's orbital altitude, the gravity from the Earth is 88% of that at sea level. The state of weightlessness is due to the constant free fall of the ISS, which according to the equivalence principle, is indiscernible from being in a state of zero gravity. The environment on the station is often described instead as microgravity, due to four effects:

• The drag resulting from the residual atmosphere.
• Vibratory acceleration due to mechanical systems and the crew on board the ISS.
• Orbital corrections by the on-board gyroscopes (or thrusters).
• The spatial separation from the real center of mass of the ISS, with a level of gravity on the order of 2 to 1,000 millionths of one g (the value varies with the frequency of the disturbance, with the low value occurring at frequencies below 0.1 Hz, and the higher value at frequencies of 100 Hz or more).^[22]

[edit] Atmosphere

The atmosphere on board the ISS is maintained to have a composition similar to that of the Earth's atmosphere.^[23] Normal air pressure on the Space Station is 101.3 kPa (14.7 psi),^[24] the same as at sea level on Earth. This does not match the atmosphere on the space shuttle, so adjustments are performed during visits.

[edit] Life support

The ISS Environmental Control and Life Support System provides or controls elements such as atmospheric pressure, fire detection & suppression, oxygen levels and water supply, among other things. The Elektron system generates oxygen aboard the station. The highest priority for the life support system is the ISS atmosphere, but the system also collects, processes, and stores waste and water produced and used by the crew. For example, the system recycles fluid from the sink, shower, urine, and condensation. Activated charcoal filters are the primary method for removing byproducts of human metabolism from the air.^[25]

[edit] Life on board

[edit] Expeditions

See also: List of International Space Station Expeditions

All permanent station crews are named "Expedition n", where n is sequentially increased after each expedition. Expeditions have an average duration of half a year and are often considered synonymous with "Increments." However, "Increments" are distinguished from Expeditions as the program planning period for activities that are to occur during a particular Expedition's residence on ISS. The start of both an Expedition and an Increment is defined by the departure of the previous Expedition crew on a Soyuz spacecraft. The definition of the Increment is in flux in preparation for 6-person crews that will be broken up into 3-person crews which overlap in their 6-month missions on ISS.

The International Space Station is the most-visited spacecraft in the history of space flight. As of April 11 2008, it has had 213 (non-distinct) visitors. Mir had 137 (non-distinct) visitors (See Space station). The number of distinct visitors of the ISS is 164. The current expedition to ISS is Expedition 18.^[26]

[edit] Crew schedule

The ISS uses Coordinated Universal Time (UTC, sometimes informally called GMT) to regulate its onboard day. This is roughly equidistant between its two control centres in Houston and Moscow. The windows are covered at "night" to give the impression of darkness since it experiences 16 sunrises & sunsets a day. During visiting shuttle missions, the ISS crew will mostly follow the shuttle's Mission Elapsed Time (MET), which is a flexible timezone based solely on the launchtime of the shuttle mission.^[27][28] Because the sleeping periods between the UTC timezone and the MET usually differ, the ISS crew often has to adjust their sleeping pattern before the shuttle arrives and after it leaves to shift from one timezone to the other, a practise known as sleepshifting.

A typical day for the crew would begin with a wake-up at 06:00, followed by 'post-sleep' activities and a morning inspection of the station. The crew then breakfasts, and takes part in a daily planning conference with Mission Control on the ground, before starting work at around 08:10. The first scheduled exercise of the day follows, after which the crew continues work until 13:05, at which point they have a one-hour lunch break. The afternoon consists of more exercise and work, before the crew carries out its 'presleep' activities, beginning at 19:30, including dinner and a crew conference. The scheduled sleep period begins at 21:30, at which point the daily schedule is complete. In general, the crew works 10 hours per day on a weekday, and 5 hours on Saturdays, with the rest of the time being their own, for relaxation, games or work catch-up.^[29]

[edit] Scientific research

One of the main goals of the ISS is to provide a place to conduct experiments that require one or more of the unusual conditions present on the station. The main fields of research include biology (including biomedical research and biotechnology), physics (including fluid physics, materials science, and quantum physics), astronomy (including cosmology), and meteorology.^[30][31] The 2005 NASA Authorization Act designated the U.S segment of the International Space Station as a national laboratory with a goal to increase the utilization of the ISS by other Federal entities and the private sector. As of 2007, little experimentation other than the study of the long-term effects of microgravity on humans has taken place. With four new research modules set to arrive at the ISS by 2011, however, more specialized research is expected to begin.

[edit] Scientific ISS modules

The Destiny laboratory is the main research facility currently aboard the ISS. Produced by NASA and launched in February 2001, it is a research facility for general experiments, providing space for 24 International Standard Payload Racks, some of which are used for environmental systems and living equipment. Destiny also features a 20 inch, optically perfect window, the largest such window ever produced for use in space.^[32][33]

The Columbus module is another research facility, designed by the ESA for the ISS. Launched in February 2008, it provides a generic laboratory as well as facilities specifically designed for biology, biomedical research and fluid physics. The laboratory also provides external mounting locations for experiments such as the European Technology Exposure Facility, Solar Monitoring Observatory,Materials International Space Station Experiment and Atomic Clock Ensemble in Space. There are also a number of planned expansions that will be implemented to study quantum physics and cosmology.

The Japanese Experiment Module, also known as Kibō, was put in service during STS-124 on June 3, 2008. It was developed by JAXA to function as an observatory and to gather astronomical data. The module also provides an external platform, the Exposed Facility, that allows payloads to be directly exposed to the harsh space environment, and which is serviced by the module's own robotic arm, the JEM-RMS.

The ExPRESS Logistics Carriers, developed by NASA, are set to be launched for the ISS beginning with STS-129, which is expected to take place no earlier than September 11, 2009.^[34] They will allow experiments to be deployed and conducted in the vacuum of space and will provide the necessary electricity and computing to locally process data from experiments. Finally, the Multipurpose Laboratory Module, created by the RKA, is expected to launch for the ISS in December 2011, and will be the primary Russian laboratory on the station.^[13] It will supply the proper resources for general microgravity experiments.^[35]

Several planned research modules have been cancelled, including the Centrifuge Accommodations Module (used to produce varying levels of artificial gravity) and two Russian Research Modules (used for general experimentation).

[edit] Areas of research

There are a number of plans to study biology on the ISS. One goal is to improve understanding of the effect of long-term space exposure on the human body. Subjects such as muscle atrophy, bone loss, and fluid shifts are studied with the intention to utilize this data so space colonization and lengthy space travel can become feasible. The effect of near-weightlessness on evolution, development and growth, and the internal processes of plants and animals are also studied. In response to recent data suggesting that microgravity enables the growth of three-dimensional human body-like tissues and that unusual protein crystals can be formed in space, NASA has indicated a desire to investigate these phenomena.^[30]

NASA would also like to study prominent problems in physics. The physics of fluids in microgravity are not completely understood, and researchers would like to be able to accurately model fluids in the future. Additionally, since fluids in space can be combined nearly completely regardless of their relative weights, there is some interest in investigating the combination of fluids that would not mix well on Earth. By examining reactions that are slowed down by low gravity and temperatures, scientists also hope to gain new insight concerning states of matter (specifically in regards to superconductivity).^[30]

Additionally, researchers hope to examine combustion in the presence of less gravity than on Earth. Any findings involving the efficiency of the burning or the creation of byproducts could improve the process of energy production, which would be of economic and environmental interest. Scientists plan to use the ISS to examine aerosols, ozone, water vapor, and oxides in Earth's atmosphere as well as cosmic rays, cosmic dust, anti-matter, and dark matter in the Universe.^[30]

The long-term goals of this research are to develop the technology necessary for human-based space and planetary exploration and colonization (including life support systems, safety precautions, environmental monitoring in space), new ways to treat diseases, more efficient methods of producing materials, more accurate measurements than would be impossible to achieve on Earth, and a more complete understanding of the Universe.^[30][31]

[edit] Future of the ISS

NASA Administrator Michael D. Griffin says the International Space Station has a role to play as NASA moves forward with a new focus for the manned space program, which is to go out beyond Earth orbit for purposes of human exploration and scientific discovery. "The International Space Station is now a stepping stone on the way," says Griffin, "rather than being the end of the line".^[36] Griffin has said that station crews will not only continue to learn how to live and work in space, but also will learn how to build hardware that can survive and function for the years required to make the round-trip voyage from Earth to Mars.^[36]

In an internal e-mail leaked to the press on August 18, 2008 from Griffin to NASA managers,^[37][38][39] Griffin apparently communicated his belief that the current U. S. administration had made no viable plan for U. S. crews to participate in the ISS beyond 2011, and that the Office of Management and Budget and Office of Science and Technology Policy were actually seeking its demise.^[38] The email appeared to suggest that Griffin believed the only reasonable solution was to extend the operation of the space shuttle beyond 2010, but noted that Executive Policy (ie, the White House) was firm that there will be no extension of the shuttle retirement date, and thus no US capability to launch crews into orbit until the Ares I/Orion system becomes operational in 2014, at the earliest.^[38] He did not see purchase of Russian launches for NASA crews as politically viable following the 2008 South Ossetia war, and hoped the incoming U. S. administration would resolve the issue in 2009 by extending shuttle operations beyond 2010.

On September 7, NASA released a statement regarding the leaked email, in which Griffin said: "The leaked internal email fails to provide the contextual framework for my remarks, and my support for the administration's policies. Administration policy is to retire the shuttle in 2010 and purchase crew transport from Russia until Ares and Orion are available. The administration continues to support our request for an INKSNA exemption. Administration policy continues to be that we will take no action to preclude continued operation of the International Space Station past 2016. I strongly support these administration policies, as do OSTP and OMB."^[40]

On October 15, 2008, President Bush signed the NASA Authorization Act of 2008, giving NASA funding for one additional mission to "deliver science experiments to the station".^{[41][42][43][44]} The Act allows for a possible additional shuttle flight to the ISS to install the Alpha Magnetic Spectrometer, which was previously canceled.^[45]

As president-elect, Barack Obama has supported the continued operation of the station, and supported the NASA Authorization act of 2008.^[45] Obama's plan for space exploration includes finishing the station, and completion of the Orion spacecraft program.^[46]

[edit] Visiting spacecraft

• American (NASA) Space Shuttle - resupply vehicle, assembly and logistics flights and crew rotation (to be retired in 2010)
• Russian (Roskosmos) Soyuz spacecraft - crew rotation and emergency evacuation, replaced every 6 months
• Russian (Roskosmos) Progress spacecraft - resupply vehicle
• European (ESA) Automated Transfer Vehicle (ATV) - resupply vehicle

[edit] Currently docked

As of 2008-11-18:

• Soyuz TMA-13 is at the Zarya nadir port
• Space Shuttle Endeavour (STS-126) is at the Harmony PMA-2 port
• MPLM Leonardo is at the Harmony nadir port

[edit] Planned

• Japanese (JAXA) H-II Transfer Vehicle (HTV) resupply vehicle for Kibo module (scheduled for 2009)^[47]
• SpaceX Dragon for NASA Commercial Orbital Transportation Services (scheduled for 2009)
• Orbital Sciences Cygnus for NASA Commercial Orbital Transportation Services (scheduled for 2010)^[48]
• American (NASA) Orion for possible crew rotation and as resupply transporter (scheduled for 2014)
• European-Russian Crew Space Transportation System (Soyuz-derived) crew rotation and resupply spacecraft (scheduled for 2014)

[edit] Cancelled

• Russian (Roskosmos) Space Shuttle Kliper for possible crew rotation and as resupply transporter
• Kistler K-1 for NASA Commercial Orbital Transportation Services^[49]

[edit] Political and financial aspects

Main article: Political and financial aspects of the ISS

As a multinational collaborative project, the legal and financial aspects of the ISS are detailed and complex — governing ownership of modules, crewing & utilization of the station, and responsibilities for station resupply.

The main legal document establishing obligations and rights between the ISS partners is the Space Station Intergovernmental Agreement (IGA), an international treaty signed on January 28 1998 by fifteen governments involved in the Space Station project. This set the stage for a second layer of agreements, called, Memoranda of Understanding, between NASA and Roskosmos, ESA, CSA and JAXA. These are further split into contractual abligations between nations, trading of partners rights and obligations, and so on. Use of the Russian Orbital segment is also negotiated at this level, whereas usage the other sections of the station have been agreed to be utilised as follows:

1. Columbus: 51% for ESA, 49% for NASA and CSA (CSA has agreed with NASA to use 2.3% of all non-Russian ISS structure)
2. Kibo: 51% for JAXA, 49% for NASA and CSA (2.3%)
3. Destiny Lab: 100% for NASA and CSA (2.3%) as well as 100% of the truss payload accommodation
4. Crew time and power from the solar panel structure, as well as rights to purchase supporting services (upload/download and communication services) 76.6% for NASA, 12.8% for JAXA, 8.3% for ESA and 2.3% for CSA

The most cited figure of an estimate of overall costs of the ISS ranges from 35 billion to 100 billion USD.^[50] ESA, the only agency actually stating potential overall costs on its website, estimates €100 billion.^[51] Giving a precise cost estimate for the ISS is not straightforward, as it is difficult to determine which costs should actually be contributed to the ISS program, or how the Russian contribution should be measured.

[edit] Miscellany

[edit] Sightings

Due to the size of the International Space Station, which is the size of an American football field, and particularly due to the large reflective area offered by its solar panels, ground based observation of the station is possible with the naked eye if one is within 63 degrees latitude. In many cases the station is one of the brightest naked-eye objects in the sky, though it is only visible for brief periods of time. This is because the station is in low earth orbit, and the sun angle and observer locations need to coincide.^[52]

[edit] Space tourism

As of 2008 there have been six space tourists to the ISS, each paying around US $25 million; the tourists, or Spaceflight participants, were launched and returned via Russian crew rotation missions on Soyuz spacecraft. In addition, the ISS was the location for the first 'space wedding', during which Russian cosmonaut Yuri Malenchenko, flying Expedition 7, married Ekaterina Dmitrieva, who was in Texas at the time.

[edit] ISS golf event

Golf Shot Around The World was an event in which, on an EVA, a special golf ball, equipped with a tracking device, was hit from the station and sent into its own low Earth orbit for a fee paid by a Canadian golf equipment manufacturer to the Russian Space Agency. The task was supposed to be performed on Expedition 13, but the event was postponed, and took place on Expedition 14.^[53]

[edit] Paper aeroplane launch

See also: Origami airplane launched from space

Japanese scientists and origami masters propose to launch a flotilla of paper planes from the ISS in early 2009.^[54] Around 30 planes will make the descent, each gliding downward over what is expected to be the course of several months. If one of the planes survives to Earth, it will have made the longest flight ever by a paper plane, traversing some 400km, and will have demonstrated the feasibility of slow-speed, low-friction atmospheric reentry. A prototype of the origami aeroplane passed a durability test in a wind tunnel in March 2008, and Japan's space agency adopted it for feasibility studies.^[55]

[edit] Major incidents

[edit] 2003 – Columbia disaster

The Space Shuttle Columbia disaster on February 1, 2003, resulted in a two-and-a-half-year suspension of the US shuttle program. Another one-year suspension following STS-114 due to continued foam shedding on the external tank resulted in some uncertainty about the future of the International Space Station. All crew exchanges between February 2003 and July 2006 were carried out solely using the Russian Soyuz spacecraft (STS-114 in July 2005 was a logistics-only visit). Starting with Expedition 7, two-astronaut caretaker crews were launched in contrast to the previously launched crews of three. Because the ISS had not been visited by a shuttle for an extended period, a larger than planned amount of waste had accumulated, temporarily hindering station operations in 2004, but automated Progress transports and the STS-114 shuttle flight resolved the problem.

[edit] 2006 – Smoke problem

On September 18 2006, the Expedition 13 crew activated a smoke alarm in the Russian segment of the International Space Station when fumes from one of the three oxygen generators triggered momentary fear about a possible fire. Flight engineer Jeffrey Williams reported an unusual smell, but officials said there was no fire and the crew was not in any danger.

The crew initially reported smoke in the cabin, as well as a smell. It was later found to be caused by a leak of potassium hydroxide from an oxygen vent. The equipment was turned off. Potassium hydroxide is odorless and the smell reported by Williams more likely was associated with an overheated rubber gasket in the Elektron system.

In any case, the station's ventilation system was shut down to prevent the spread of smoke or contaminants through the rest of the lab complex. A charcoal air filter was put in place to help scrub the atmosphere of any lingering potassium hydroxide fumes. The space station's program manager said the crew never donned gas masks, but as a precaution put on surgical gloves and masks to prevent contact with any contaminants.^[56]

On November 2 2006, the payload brought by the Russian Progress M-58 allowed the crew to repair the Elektron using spare parts.^[57]

[edit] 2007 – Computer failure

On June 14 2007 during Expedition 15 and flight day 7 of STS-117's visit to ISS, a computer malfunction on the Russian segments at 06:30 UTC left the station without thrusters, oxygen generation, carbon dioxide scrubber, and other environmental control systems, and caused the temperature on the station to rise. A successful restart of the computers resulted in a false fire alarm that woke the crew at 11:43 UTC.^[58][59] The two computer systems (command and navigation) are each composed of three computers. Each computer is referred to as a "lane".^[59]

By June 15, the primary Russian computers were back online, and communicating with the US side of the station by bypassing a circuit. Secondary systems were still offline, and further work was needed.^[60] NASA reported that without the computer that controls the oxygen levels, the station had 56 days of oxygen available.^[61]

By the afternoon of June 16, ISS Program Manager Michael Suffredini confirmed that all six computers governing command and navigation systems for Russian segments of the station, including two thought to have failed, were back online, and would be tested over several days. The cooling system was the first system brought back online. NASA suggested that the overcurrent protection circuits designed to safeguard each computer from power spikes were at fault, and may have been tripped due to increased interference, or "noise," from the station's plasma environment related to the addition of the new starboard trusses and solar arrays.^[59] Troubleshooting of the failure by the ISS crew found that the root cause was condensation inside the electrical connectors, leading to a short-circuit that triggered the "power off" command line leading to all three of the redundant processing units.^[62] This was initially a concern, because the European Space Agency uses the same computer systems, supplied by EADS Astrium Space Transportation, for the Columbus Laboratory Module and the Automated Transfer Vehicle.^[63] Once the root cause was understood, plans were implemented to avoid the problem in the future.

[edit] 2007 – Torn solar panel

On October 30, 2007 during Expedition 16 and flight day 7 of STS-120's visit to ISS, following the reposition of the P6 truss segment, ISS and Space Shuttle Discovery crew members began the deployment of the two solar arrays on the truss. The first array deployed without incident, and the second array deployed approximately 80% before astronauts noticed a 76 centimetre (2.5 ft) tear. The arrays had been deployed in earlier phases of the space station's construction, and the retraction necessary to move the truss to its final position had gone less smoothly than planned.^[64]

A second, smaller tear was noticed upon further inspection, and the mission's spacewalks were completely replanned in mere days to devise a repair - normally such spacewalks take several months to plan and are settled upon well in advance. On November 3, spacewalker Scott Parazynski assisted by Douglas Wheelock fixed the torn panels using makeshift "cufflinks" and riding on the end of the space shuttle's boom inspection arm; the first ever spacewalker to do so. The spacewalk was regarded as significantly more dangerous than most due to the possibility of shock from the electricity generating solar arrays, the unprecedented usage of the shuttle boom arm, and the lack of spacewalk planning and training for the impromptu procedure. Parazynski was, however, able to repair the damage as planned and the repaired array was fully deployed.^[65]

[edit] 2007 – Damaged starboard Solar Alpha Rotary Joint

This article or section documents a current or recent spaceflight. Details may change as the mission progresses.

During STS-120, a problem was detected in the starboard Solar Alpha Rotary Joint (SARJ) which, together with a similar device on the port side of the station's truss structure, rotates the large solar arrays to keep them facing the Sun while the ISS's main body axis remains horizontal, pointing forward in the direction of orbital motion. Excessive vibration and high current spikes in the array drive motor were noted, resulting in a decision to substantially curtail motion of the starboard SARJ until the cause was understood. Inspections during EVAs on STS-120 and STS-123 showed extensive contamination from metallic shavings and debris in the large drive gear, and confirmed damage to the large metallic race ring at the heart of the joint.^[66] The joint is currently locked in place, and currently the station appears to have sufficient operating power to carry out its near-term science program with only modest impact on operations.

On September 25 2008, NASA announced significant progress in diagnosing the source of the starboard SARJ problem, and a programme to repair it on orbit, beginning with the flight of the Space Shuttle Endeavour on the current STS-126 mission, which launched on 15 November 2008.^[13] STS-126 is a 15-day mission with four EVAs, largely dedicated to servicing and repair of the Solar Alpha Rotary Joints, plus station logistics and resupply. The crew will carry out servicing of both the starboard and port SARJs, lubricating both bearings and replacing the remaining 11 Trundle Bearings in the starboard SARJ.^[67]

[edit] See also

• List of International Space Station visitors
• List of ISS spacewalks performed from the ISS or visiting spacecraft
• List of manned spaceflights to the ISS for a comprehensive chronological list of all manned spacecraft that have visited the ISS, including the spacecraft's respective crews
• List of unmanned spaceflights to the ISS — Progress supply flights and unmanned automatic docking space station modules

[edit] References