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Table 1. Major ISS Elements to be Provided by the International Partners

United States Russia

¥ Space Station infrastructure elements ¥ Space Station infrastructure elements¥ Laboratory modules and equipment for attached ¥ Research modules and equipment for attachedpayloads payloads

¥ Flight elements to supply ISS ¥ Flight elements to supply and reboost ISS¥ Ground infrastructure elements ¥ Ground infrastructure elements

Canada Europe Japan

¥ Mobile servicing system ¥ Columbus Laboratory ¥ Japanese Experiment Module¥ Special Purpose Dexterous ¥ Automated Transfer Vehicle ¥ Japanese Exposure FacilityManipulator ¥ Outfitting Elements ¥ Flight elements to supply ISS

¥ Ground infrastructure elements

This chapter provides an overview of thetechnical characteristics of the ISSelements as a prelude to the detailedutilisation accommodation and resourceinformation given in the followingchapters.

BackgroundA new Intergovernmental Agreement(IGA) was concluded on 29 January 1998between the governments of the fiveInternational Partners – Europe (11participating States), Canada, Japan,Russia and USA. This new IGA enlargesthe earlier 1988-partnership agreementby including Russia in the largestinternational cooperative civil spaceprogramme ever undertaken.

It is the responsibility of the US NationalAeronautics and Space Administration(NASA) to lead the ISS programmedevelopment and implementation, and inconjunction with the Russian Space

Agency (RSA) provide the majorfoundation blocks for the Station(Table 1). The European Space Agency(ESA) and the National SpaceDevelopment Agency of Japan (NASDA)provide additional elements thatsignificantly enhance those blocks, andthe Canadian Space Agency (CSA)provides an essential mobile roboticsservicing capability.

The provision of these elements giveseach ISS Partner certain rights for Stationutilisation as well as participation in itsmanagement and operations. Forexample, each Partner has the right toprovide suitably qualified flight crew.Each Partner may also access the Stationusing its own transportation system.Nevertheless, each Partner has todevelop and maintain the elements thatit provides, as well as participate in theequitable sharing of the Station'scommon operating costs.

International SpaceStation Overview

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Fig. 1. The ISS orbitprovides coverage ofmost of the world’sinhabited regions.

ESA has acquired through itscontributions the following utilisationshares:

• 51% usage of the useraccommodation of the ColumbusLaboratory, incl. attachment points

• 8.3% usage of the on-orbit utilisationresources (eg electrical power, crewtime), as well as the right to purchaselaunch & return, and Tracking & DataRelay Satellite (TDRS) systemcommunications services.

ESA has acquired further crew flightopportunities commensurate with itsutilisation resources allocation.

ISS: General DescriptionThe Space Station will be a permanentlyinhabited outpost in low Earth orbit andcomposed of flight elements, provided byall five Partners, and associated groundelements to support on-orbit operationsand utilisation.

A summary of the ISS key characteristicsat the end of the 5-year build-up periodis provided in Table 2. ISS assemblybegan in November 1998 with thelaunch of the US-procured/Russian-built‘Zarya’ Control Module.

On the second assembly flight, inDecember 1998, the US-built ‘Unity’resource node was attached to Zarya.This will be followed by the thirdassembly flight with the Russian-builtService Module. A 3-person PermanentInternational Human Presence Capabilitywill then begin in early 2000. At thattime, the ISS will already be flying at anaverage altitude of 407 km in its 51.6°inclination orbit (Fig. 1).

European users will have some earlypayload utilisation opportunities beforethe launch of the Columbus Laboratory,once the US Laboratory module is on-orbit and operational for users, as well as on the Integrated Truss Assemblyfollowing the check-out of the MobileRemote Servicer Base System (MBS) andthe arrival of the first Express Pallets forexternal payloads in 2002.

Table 2. ISS Characteristics at Completion

Truss length 108 mTotal module length 74 mMass about 420 t

Maximum power 110 k Woutput

Pressurised volume 1200 m 3

Atmospheric pressure 1013 mbar

Orbital altitude 370-460 kmOrbital inclination 51.6…Orbital velocity 29 000 km/hAttitude local horizontal/vertical

Minimum crew 6

Data rate uplink 72 kbit/sDate rate downlink 150 Mbit/sKu-band coverage 68%S-band coverage 50%

Expected lifetime >10 years

The 6-person Permanent InternationalHuman Presence Capability will beestablished in late 2002. The ColumbusLaboratory will be coupled to the ISS earlyin 2003 and Station assembly will becompleted (Fig. 2) with the launch of theUS Habitation module.

A summary of the major ISS elements,their first year on-orbit according toAssembly Sequence Revision D, and theirpotential availability for utilisation arepresented in Tables 3 and 4.

Fig. 2. ISSconfiguration when

assembly is completedin 2004.

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Table 3. Principal ISS Pressurised Elements

On-orbit Outer Dimensions Number ofPressurised Element (year) (length x diameter) ISPRs Comments

Zarya Control Module 1998 12.6x4.1 m Provides initial(FGB) propulsion and power

Unity Node-1 1998 5.5x4.6 m Connector node forpressurised modules

Service Module 1999 13.1x29.6 m Early crew living and(including working quarters. solar panels) Limited possibilities

for payloads

3-person Permanent 2000 Soyuz crew returnInternational Human vehicle docked to ISSPresence Capability

US Laboratory module 2000 8.2x4.4 m 13

Node-2 2001 6.4x4.6 m

Japanese Experiment 2002 11.2x4.4 m 10 Including ExposedModule (JEM) Facility

Cupola 2002 360… viewing window

Russian Research 2002 Design details Design detailsModule-1 not available not available

Node-3 2002 6.4x4.6 m

Russian Research 2002 Design details Design detailsModule-2 not available not available

6-person Permanent late 2002International HumanPresence Capability

Columbus Laboratory 2003 6.1x4.4 m 10 Launched with 5outfitted ISPRs

Centrifuge 2003 4 Contains a 2.5 m-diaAccommodation centrifuge for glevels Module (CAM) 0.01-2 g

US Habitation module 2004 8.2x4.4 m

Table 4. Principal ISS Unpressurised Elements

On-orbit Outer PayloadUnpressurised Element (year) Size Adapters Comments

Space Station Remote 2000 17 m length Initially a measuring wormManipulator System capability (until MT available) to(SSRMS) support ISS assembly & Orbiter

cargo bay loading & unloading

Mobile Transporter 2000 Provides structural, power, data and (MT) video links between ISS and MBS

Mobile Remote Servicer 2000 Serves as stable base for Base System (MBS) SSRMS

Integrated Truss 2002 108 m length 24 Utilisation start after MBSAssembly (ITA) commissioning

JEM-Exposed Facility 2002 5x5.2 m 10widthxlength

Special Purpose 2002 two Extends SSRMS capability forDexterous 3.5 m-long intricate manipulationsManipulator (SPDM) arms

Columbus-External 2003 4Payload Facility (EPF)

The major elements of the Station include:

• modules and nodes housing essentialsystems, providing a habitableenvironment and serving as pressurisedpayload laboratories;

• the 108 m-long Truss is a majorstructural framework mounted onUnity (Node-1). It provides the ISS‘backbone’ and interconnectionbetween the pressurised modules,external payloads and systemsequipment. It also hosts umbilicals,radiators, communications antennas,batteries, Mobile Transporter rails andmechanical systems such as joints andmechanisms. Truss segments arelocated on the starboard and portsides, and labelled accordingly. Forexample, the P6 section is on theoutermost port side;

• the Mobile Servicing Center and MobileTransporter make up the MobileRemote Servicer Base System that willbe used to remove payloads from theShuttle cargo bay and transport themto designated locations on the outpost.The 17 m-long remote manipulator armcan carry payloads of up to 128 t,while the Special Purpose DexterousManipulator (SPDM), with two armseach 3.5 m long, can perform moredelicate tasks such as connectingutilities or exchanging small hardwareitems.

Payload Transportation andLogistics CarriersA mixed fleet of launch vehicles ispotentially available for the transportation

of payloads. It includes:

• US Space Shuttle;• Russian Proton;• European Ariane-5;• Japanese H-IIA.

The US Space Shuttle is the prime vehiclefor transporting system elements, logistics,crew and payloads (including theColumbus Laboratory) to the Station. Forthe assembly of the Station from 1998 to2004, some 34 Shuttle flights areprojected, including several user-orientedflights. The Shuttle-to-Station cargooptions also include:

• the Italian-built Mini PressurisedLogistics Module (MPLM) fortransporting pressurised cargo to/fromthe Station, accommodating 16 rackscomprising five powered for

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Fig. 3. ESA’s Automated Transfer Vehicle (ATV) willtransport mixed cargo items to/from the ISS.

(ESA/D. Ducros)

Distributed Station SystemsCommand & Data Handling (C&DH)SystemAs the ‘brain’ of the ISS, the C&DH system(Fig. 4) monitors all aspects of the Station’soperations. Furthermore, it distributespayload and systems data to the crew,and to personnel on Earth via the Trackingand Data Relay Satellite (TDRS) system.

C&DH hardware includes data processors,control and monitoring processors, crewinterface computers, data acquisition anddistribution networks, and interfaces tosystems and payloads. The C&DH datadistribution architecture relies heavily onnetwork technology, and is composed ofthree major components: local areanetworks (LANs) based upon IEEE 802.3;local data buses based upon MIL-STD-1553B; and high-rate data (HRD) links.

Even during the early stages of assembly,system and payload networks will beprovided throughout the evolving Stationto link all system and payload data units.The networks will be extended as theStation matures, with system and payloadnetworks being routed through the Nodes,US Laboratory, JEM, Columbus Laboratoryand the Russian Research Modules.

The MIL-STD 1553 data bus provides alow-rate data transfer capability; the IEEE802.3 data bus provides a medium-ratedata transfer capability. The HRD linkprovides payloads with return data rateshigher than can be met by the LANs.

Laptops are available for the crew to:interface with the data system; monitorand control systems; display video, and

refrigerators, freezers or active payloadsand 11 racks for passive payloads;

• Unpressurized Logistics Carrier (ULC)for transporting external systems andpayloads to/from the Station.

The Russian Proton is the prime vehiclefor transporting the Russian pressurisedand unpressurised elements to theStation. The Soyuz rocket will be used fordelivering the Soyuz crew vehicle and theProgress cargo spacecraft.

The European Ariane-5 is the vehicle forlaunching the Automated Transfer Vehicle(ATV; Fig. 3) that will be used for transportingmixed cargo items to/from the Station.

The Japanese H-IIA is the prime vehiclefor launching the H-II Transfer Vehicle(HTV) that will be used for transportingmixed cargo items to the Station.

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payload and system data; and communicatewith the ground. The crew Man MachineInterfaces for all the Station laptops aresimilar and the data displayed on themcan also be displayed on monitors on Earth.

A stable frequency and time reference isprovided by the C&DH time distributionsystem.

The interface between the Columbusprocessors and the Columbus payloads isachieved over the Utility Interface Panel;this is detailed in later chapters.

Payload users may develop and providetheir own application software forintegration into the element payloadcomputers. However, the interfaces forthe bulk of such applications consistprimarily of standard services. Thesestandard services provide payload andcore systems with access to datacommunications, data acquisition andcommanding and timing information.Payloads are required to use standard

services for commands, and for allcommunications with the LANs and buses.

Communications and TrackingSystem (C&TS)The C&TS provides audio, data and videocommunications with the ground andother spacecraft. Payload commands andaudio may be transmitted from the groundto the Station. The downward (‘return’)usable data transmission capability is viathe Ku-band system. The upward(‘forward’) transmission capability is via anS-band system from the ground forStation systems and payload operations.

The European end-to-end communicationsinfrastructure is shown in Fig. 5.

NASA’s TDRS system is the primary Stationdata and communications link with theground. Data and commands aretransmitted to/from the Station via TDRSto White Sands in New Mexico. The dataare then distributed through a combinationof satellite and terrestrial links.

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Fig. 4. Overview of theISS Command & Data

Handling System.MDM: Multiplexer/

Demultiplexer. C&T: Communications

& Tracking. USL: US Laboratory.

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The pulse frequency-modulated onboardvideo signals, distributed by fibre opticanalog video lines, are compatible withthe NTSC standard.

The JEM and Columbus Laboratory havevideo and audio systems that arecompatible with the US network. Videoand audio signals are digitised, assembledinto data transfer frames (packets), andmultiplexed with other data for Ku-banddownlink transmission. Video, audio anddata signals have time synchronisation forproper time stamping and voice/datacorrelation. However, the Russianelements use the SECAM video standardand there is no video connectivity withthe other Partner video systems.

Electrical Power System (EPS)Two parallel sets of solar array wingsgenerate the primary Station power.Nickel-hydrogen batteries store the dcpower generated by the solar arrays foruse when the station is in the Earth’sshadow. 18.75 kW of orbital average

The TDRS system and Station are incommunication for most of each orbitexcept for a brief period known as theZone of Exclusion (ZOE) when there is noTDRS-to-ground coverage, or duringparticular Station attitudes when there isno line-of-sight link between the Stationand TDRS. The coverage period canrange up to 60 min in any one 90 minorbit. During this time, users are able totransmit or receive data. There is also avery short period of disruption (of theorder of 2 min each orbit) whencommunications are being handed overfrom one TDRS to the other.

As an additional link, communications viathe Japanese (DRTS) and European(Artemis) data relay systems are underconsideration (Fig. 5).

Video cameras are located throughoutthe pressurised elements and on theTruss. The Video Switching Unit (VSU)allows images from any Station-suppliedcamera to be displayed on any monitor.

Fig. 5. The Europeancommunicationsinfrastructure for ISS.APS: AutomatedPayload Switch. C&CMDM: Command &Control Multiplexer/Demultiplexer. C&T: Communications& Tracking. DRTS: Data Relay &Test Satellite. SSCC: Space StationControl Center. SSIPC: Space StationIntegration &Promotion Centre.SSMB: Space StationManned Base.

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Presence Capability, a moderate-temperature (17°C) loop will also beavailable, bringing the total heat rejectioncapacity for all pressurised elements to75 kW.

No active thermal control system isprovided for attached payloads mountedon the Truss.

Guidance, Navigation and Control(GN&C)The GN&C system maintains the Stationattitude and orbit control that is optimisedfor the proper microgravity environmentin support of payload requirements. Inaddition, GN&C controls include debrisavoidance, reboost and rendezvousoperations. The GN&C system can providethe Station’s exact orbital speed, attitudeand altitude as telemetry to payloads.

Flight Crew SystemsFlight crew systems include restraints andmobility aids, portable emergency provisions,housekeeping and trash management,Crew Health Care System (CHeCS),lighting, personal hygiene equipment,wardroom and crew privacy. They providethe crew with a safe environment and thebasic necessities for life.

The most complex of these, CHeCS,comprises the Health Maintenance System(HMS), the Countermeasure System (CMS)and the Environmental Health System(EHS). The HMS monitors crew health,responds to crew illness or injury,provides preventative health care, andstabilisation and emergency transportbetween vehicles. The CMS evaluates

power is generated initially, increasing to110 kW with the full Station capability.The EPS provides 120 Vdc power to theuser interface. The Russian segment alsogenerates additional electrical power, forthe Russian elements.

Thermal Control System (TCS)The TCS maintains the Station’s structure,systems, equipment and payloads withintheir allowable temperature ranges. Heatrejection is achieved through two largeradiators attached to the Truss.

A passive thermal control system isprovided through insulation coatings andheaters, and is responsible formaintaining Station structures andexternal equipment within allowabletemperature ranges.

An active thermal control system isprovided through mechanically-pumpedfluid in closed loop circuits and isresponsible for heat collection, heattransportation and heat rejection withinthe pressurised elements. Water is used inthe active system within the pressurisedelements; anhydrous-ammonia is used inthe active system in the external areas.Both fluids remain in a liquid state.

Initially, two low-temperature (4°C) loopsprovide a total of 14 kW heat rejection. At6-person Permanent International Human

Information ServicesThe Station programme coordinates andsustains diverse information servicesrequired for Station operations. Theseinclude command & control services,payload support services and automatedinformation security services.

Command & control services provide forthe interactive control and monitoring ofpayloads, elements and systems, as wellas for the acquisition, transmissionprocessing, storage and exchange of dataamong Partner system and payloadoperators and users. Within the Europeanscenario, these services include informationexchange between the ISS and the:

• Mission Control Center-Houston (MCC-H), responsible for integratedStation operations;

• Payload Operations Integration Center(POIC), responsible for consolidatingthe planning and execution of allelement payload operations;

crew fitness, provides countermeasuresfor musculoskeletal and cardiovasculardeconditioning, and monitors the crewduring countermeasures. The EHSmonitors the Station’s internalenvironment and includes instrumentsfor microbiological, toxicological,radiation and acoustics measurements.CHeCS interfaces with the C&DH systemto provide onboard data display and datatransmission to the ground.

Environmental Control & LifeSupport System (ECLSS)The ECLSS provides a comfortableshirtsleeve environment throughout theStation’s pressurised elements.Temperature, humidity, air compositionand atmospheric pressure are maintained,as well as nitrogen and potable watersupplies, and fire detection/suppressionequipment. The ECLSS maintains anatmospheric pressure of 978-1026 mbar(14.2-14.9 psia) with an oxygenconcentration of not more than 24.1%.

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• Columbus Control Centre, responsiblefor integrating the planning andexecution of all Columbus Laboratorypayload and system flight operations;

• User Support and Operations Centre(USOC) or Facility Responsible Centre(FRC), responsible for monitoring andcontrolling one or more payloadfacilities.

Payload support services increase theproductivity of payload user operations.Telescience, for example, allows payloadusers to access remote equipment anddatabases interactively in pursuit of theirexperimental objectives. One such aspectis the capability for users, at their homeinstitutions or User Home Base (UHB), tocontrol and monitor payloads in space.The Station delivers data to the payloaduser in the form in which it was acquiredfrom the payload onboard. The handlingand provision of ancillary data necessaryfor the meaningful processing of payloaddata is another support service. Examplesof ancillary data include orbital position,attitude references and standard timereferences, as well as physicalcharacteristics such as an element’stemperature, oxygen partial pressure, orexternal environmental parameters.

Automated information security servicescontrol access to the information networkand ensure the quality and integrity ofthe data traversing it on an end-to-endbasis. The Station does not provide dataencryption services for payload user data.However, payload users may encrypt theirdata if they wish.

Environment ConsiderationsThe natural environment existsunperturbed by the presence of theSpace Station, while the inducedenvironment exists as a result of theStation’s presence. Payload users shouldbe aware of the potential effects thatthese environments can have on payloads.

Natural EnvironmentThe neutral atmosphere is significant forStation operations for two reasons. Firstly,it produces torques and drag thatdegrade the Station’s altitude. Secondly, itaffects the flux of trapped radiationencountered by the Station.

Plasma is important to Station operationsbecause it controls the extent of spacecraftcharging, affects the propagation ofelectromagnetic waves such as radiofrequency signals, and probably contributesto surface erosion. Another importanteffect is the production of electric fields inthe structure as the Station moves acrossthe geomagnetic field.

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Charged particle radiation can havesufficient energy to penetrate severalcentimetres of metal and, afterpenetration, still produce significant levelsof ionised radiation. A high level ofradiation can significantly affect materials,chemical processes and living organisms,and especially the crew. It can also affectelectronics by causing soft upsets anddegrading the performance or producingpermanent damage. In addition, it canaffect the propagation of light throughoptical materials by altering their opticalproperties.

The Station’s systems and payloads areimmersed in electromagnetic radiation.Such radiation originates from the Earth,from plasmas surrounding the Earth, Sunand stars; and from the nearbyionosphere, and is disrupted by thepassage of the Station itself. Intenseradiation can affect the Station’s systemsor payloads.

Micrometeoroids and space debris candamage the Station and its attachedpayloads. Critical Station elements areprotected by a combination of shieldingand shadowing.

Induced EnvironmentThe Station provides an environmentsuitable for the performance ofmicrogravity experiments (Fig. 6).Acceleration levels of 1.8x10-6g or less, atfrequencies <0.1 Hz, are maintained for atleast 50% of the pressurised useraccommodation locations for continuousperiods of up to 30 days beginning at3-person Permanent International HumanPresence Capability and continuingthereafter. These conditions are providedfor at least 180 days per year. Forfrequencies of 0.1-100 Hz, theacceleration levels are less than theproduct of 18x10-5g*frequency, while forfrequencies exceeding 100 Hz,acceleration levels of 1.8x10-3g arepredicted. The Station’s use of controlmoment gyroscopes for attitude control

during normal operations minimisesvibration disturbances. However, thegreatest disturbances (~10-3g) occurduring Shuttle docking and Stationreboost.

Microgravity quiescent and non-quiescentperiods are scheduled in advance.Quiescent periods are maintained for upto 30 days, to provide optimalmicrogravity conditions. Non-quiescentperiods, such as during Station reboost,may be unacceptable for the operation ofsome payloads. The predicted quasi-steady acceleration environment is shownin Fig. 6.

The Station’s external environment will beaffected by its presence, operation andmotion with induced effects from:

• Plasma wake, the variation of plasmadensity from the ram to the wake side;

• Neutral wake, the variation of neutraldensity;

• Plasma waves induced by the Station’smotion;

• Vehicle glow on the ram or forwardside;

• Change of local plasma density andproduction of electrical noise caused byspacecraft charging;

• Enhancement of neutral density andthe change of neutral composition byoutgassing, offgassing and the plumesfrom thrusters;

• Emission of conducted and radiatedelectromagnetic power by systems onthe Station;

• Deliberate perturbation of theenvironment by active experiments anddevices such as:- Transmitters/wave injectors- Particle beam emitters- Plasma emitters- Chemical releases- Laser beams

• Visible light generated by the Stationand reflections from it;

• Induced currents and voltage potentialdifferences that are generated by themotion of the Station through Earth’smagnetic field, which can draw currentthrough the surrounding plasma.

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Figure 6. Thepredicted quasi-steady

accelerationenvironment side view.

(NASA)