r bulletin 98 — june 1999

European External Payloads Selected forEarly Utilisation on the InternationalSpace Station

R.D. Andresen and G. PetersESA Directorate of Manned Spaceflight and Microgravity,ESTEC, Noordwijk, The Netherlands

IntroductionWith the launch and subsequent coupling ofthe first two elements, ‘Zarya’ and ‘Unity’, atthe end of 1998, the build-up of theInternational Space Station has begun inearnest. In all, more than 100 elements and460 tonnes of structures, modules, equipmentand supplies will be placed in orbit by the year2004. Utilisation of ISS for different fields ofresearch will already start in 1999, increasingyear by year during the Station’s assemblyphase and keeping pace with the launch andassembly of the various modules and externalstructures designed for supporting andoperating payloads.

The external sites of the International Space Station (ISS) have hugeutilisation potential for many different space disciplines. As a platformin a high-inclination, low Earth orbit and with a lifetime of 15 years ormore, the ISS will provide payload mass, volume, power andcommunications capabilities far exceeding those of free-flyingsatellites. Every three months, the Space Shuttle and other servicingvehicles (ESA’s Automated Transfer Vehicle, Progress, etc.) will takeastronauts, new equipment and stocks of consumables up to the ISS.

The external payloads selected for the ISS assembly phase representfirst-class science, as is demonstrated for example by the fact thattwo Nobel Prize winners are involved in two of the experiment teams(for ACES and AMS). Another payload (GTS) offers commercialservices in the fields of protection against car theft, and wristwatchaccuracy control.

The first externally mounted European payloadwill be launched this year as part of the RussianService Module. Further European payloadshave already been selected and are underdevelopment. The following paragraphs brieflydescribe the opportunities offered by theStation for mounting and operating payloadsexposed to the external space environment, aswell as those European payloads that havealready been selected. Mobile Servicing System

Starboard Payload AttachSites (4) = 24 ExPas

Figure 1. Locations forattaching external payloadson the ISS

utilisation, as well as participation in itsmanagement and operation. Based upon thisformal right of access, it is possible to build upa strong, long-lasting ISS utilisation programmefor the European user communities.

The International Space Station will providebroad opportunities for researchers in the lifeand physical sciences, remote sensing, techno-logy and commercial applications sectors toexploit the unique attributes of space. Theseinclude prolonged exposure to microgravity,near-vacuum, and the space-radiation environment,but also those opportunities provided byexploiting the Station as an observationplatform for celestial- or Earth-viewing payloads.

Opportunities being offered (Fig. 1)The International Space Station is the largestinternational cooperative civil space programmeever undertaken. It is based on an Inter-Governmental Agreement (IGA) concluded inJanuary 1998 between the Governments of five‘International Partners’: the United States ofAmerica, Russia, Japan, Canada and Europe(11 States).

The European contributions to ISS include the‘Columbus’ laboratory, the Automated TransferVehicle (ATV) to supply the Station andperiodically raise its orbit, and several groundinfrastructure elements. Through its contribution,Europe has acquired certain rights for Station

european external payloads selected

Port UnpressurizedLogistics Carrier

(ULC)/Payload Attach Sites (2)

JEM ExposedFacility Sites (10)

ColumbusExternal PayloadFacility (4 ExPas)

Figure 2. The milestonesfor major utilisation-related

launches

The ISS offers a choice of several external sitesfor mounting payloads to be exposed to thesurrounding space environment:

– 4 locations on the S3 segment of the US-provided 107 m-long Station Truss

– 10 locations on the Japanese-provided JEM– 4 locations for Express Pallet Adapters on

the Columbus laboratory’s External PayloadFacility

– mounting locations on the Russian segment.

A number of experiments can already beperformed during the Assembly Phase whenthe Space Shuttle and Russian launchers visitthe Station, and between flights when the on-board crew is available as experimentoperators or as research subjects.

Sets of research hardware will be transportedto the Station primarily on dedicated ShuttleUtilisation Flights (Fig. 2). These flights will startwith UF1 in 2000 and end, according to thepresent build-up schedule, with UF7 in 2003,by which time the laboratories and external-payload sites will have been outfitted with thefirst generation of research equipment. Fromthen onwards, five Shuttle flights and additional

logistics flights by the Partners’ mixed fleet ofvehicles are planned each year for taking theastronauts to and from the Station and re-supplying ISS logistics and payload items.

The ESA AOIn December 1996, ESA issued an Announce-ment of Opportunity (AO) for ExternallyMounted Payloads during the Early SpaceStation Utilisation Period (ESA SP-1201). ThisAO was based on an ESA/NASA Agreementthat affords European payloads access to theUS-provided external Truss attach sites duringthe period 2002-2005. The AO was mailedusing user-programme distribution lists andwas also posted on the ESA Web Site. 102proposals had been received by the April 1997closing date, with the following distribution bydiscipline:

– Space Technology 48– Space Science 23– Life Sciences 14– Physical Sciences 11– Earth Observation 6

Some 350 investigators from 23 countries wereinvolved in these proposals.

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five Express Pallet payloads: ACES, EUTEF,EXPORT, FOCUS and SOLAR.

The Express Pallet SystemThe Express Pallet System (Figs. 3a,b) allowspayloads to be mounted at external sites on theISS Truss structure. This US-provided PalletSystem will be launched and retrieved by theSpace Shuttle.

The Pallets, which will be attached at specificlocations on the Truss, can be zenith- or nadir-facing, allowing them to carry instrumentsrequiring solar or celestial viewing (zenith) orEarth viewing (nadir). The Express Pallet willhouse six Adapters, each capable of carryingup to 225 kg of payload on a 1 m

2mounting

surface. ESA’s instruments will be grouped tofully occupy Adapters: the SOLAR, EXPOSE/

Figure 3a. The TrussExpress Pallet can carry sixExPAs

Figure 3b. The ExpressPallet, carrying six ExPAs,mounted on the ISS Truss(ESA/D. Ducros)

european external payloads selected

The evaluation of the science and technologyproposals was organised by each ESA userprogramme, using external peer review groups,and applying the evaluation criteria defined inthe AO. The results of the peer review werepresented to the existing ESA User AdvisoryBodies for each discipline, and ultimately to therelevant User Programme Boards. In parallel, atechnical team, including industrial contractors,began to assess the technical aspects of theproposals.

Based on the list of peer-recommended andtechnically feasible experiments, the Executivepresented the European Utilisation Board (EUB)with a list of 10 discipline-oriented groupings,each of which comprised a complement ofinstruments per Express Pallet Adapter. Fromthese 10 groupings, a final selection of 5 had tobe made. This was achieved through severaliterations, taking the following aspects intoconsideration:– funding support by Member States for the

experiments proposed– compatibility with accommodation

and/or operational constraints imposed by the Space Station

– expected readiness of payloads to meet the delivery dates for flight

– interdisciplinary aspects, the ESA SpaceStation User Panel (SSUP) havingrecommended a fair balance between thedifferent disciplines.

The final payload complement was selected bythe Manned Space Programme Board inDecember 1997 and consists of the following

Figure 4. The ACESconcept; Pharao is thelaser-controlled atomicclock and the hydrogen

maser serves as thereference clock

Figure 5. The TechnologyExposure Facility (TEF)

supports space technologyresearch and development

SPORT (EXPORT) and EUTEF packages arezenith-oriented, while ACES and FOCUS arenadir-oriented. It is planned that two of thethree Adapters will be exchanged during thethree-year mission.

The first five European payloads1. ACES – An Atomic Clock Ensemble inSpace (Fig. 4)The core of this project is a laser-cooledcaesium atomic clock (‘Pharao’), which exploitsthe microgravity conditions onboard the SpaceStation. The investigator team includesresearchers belonging to the group thatreceived the Nobel Prize for Physics in 1997.

Pharao will improve clock frequency stabilityand accuracy by a factor of 100 compared with

the best measurements currently achievable onEarth, opening up new opportunities in variousfields of fundamental research andapplications. This ultra-precise measurement oftime will allow relativistic measurements andtests, applications in atmospheric physics and geodesy, navigation and advancedtelecommunications.

The ACES Principal Investigators (PIs) are Prof. C. Salomon from the Ecole NormaleSupérieure, Paris and Prof. A. Clairon of theLaboratoire du Temps et des Fréquences,Paris. A Swiss hydrogen-maser clock providedby Dr. L.G. Bernier, also a PI, from theObservatoire Cantonal de Neuchatel,Switzerland, will serve as a reference clock. Theimportant time transfer by laser link will berealised from the Observatoire de la Côted’Azur in Grasse, France, with PIs Dr. E.Samain and Dr. P. Fridelance.

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2. EUTEF – The European TechnologyExposure Facility (Fig. 5)EUTEF is a multi-user support facility that willbe developed under the auspices of ESA’sManned Spaceflight and MicrogravityDirectorate, located at ESTEC in Noordwijk. Itwill provide modular accommodation for avariety of technology payloads requiring spaceexposure. It incorporates a material-propertieslaboratory allowing periodic onboardmeasurements of surface degradation, and a comprehensive environment-monitoringpackage to characterise the ISS spaceenvironment, including high-energy cosmicradiation, the natural and ISS-induced plasmaenvironment, atomic-oxygen concentration,etc. An ASI-provided robot arm, to beincorporated with a tele-operated intelligentgripper for payloads, will allow the servicing ofpayloads, the exchange of exposed materialwithin EUTEF modules, or the pointing ofsamples to a specific environment.

Several proposed EUTEF experiments — fromFrance, Germany, the United Kingdom, theNetherlands, Italy and Spain — have alreadybeen selected. Industrial initiatives to qualifyadvanced and innovative sensors, componentsor subsystems have been selected with thehighest priority. One example in this respect is the testing of a high-temperature super-conductor for advanced satellitecommunications.

3. EXPORT – consisting of EXPOSE andSPORT (Fig. 6a,b)Eight exobiology experiments have beenselected for accommodation on an exposure

Figure 6.a. The Sky PolarisationObservatory (SPORT) willsurvey the polarisation of the diffuse cosmicbackground radiationb. The EXPOSE unit(mounted on the CoarsePointing Device) willexpose biologicalspecimens to the spaceenvironment

unit oriented towards the Sun (Table 2). A rangeof organic molecules and micro-organisms willbe exposed unshielded to solar ultravioletradiation and the space environment (vacuum,cosmic radiation). This study of photochemicalprocesses will support conclusions as to theorigin and evolution of life, and on the survivalcapability of micro-organisms in space.

SPORT, with Principal Investigator Prof. S. Cortiglioni from the Istituto di Technologie eStudie Della Radiazioni Extraterrestri, CNR,Bologna, Italy, and further Co-Investigatorsfrom Italy and Russia, will measure thepolarisation of the sky diffuse backgroundradiation in the unexplored wavelength rangebetween 20 and 70 GHz. In this spectralrange, the galactic synchrotron radiation is thestrongest source of polarised emission;however, the detection of small contributionsfrom the linear polarisation of the cosmic

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Table 1. Instruments and experiments selected for EUTEF

Acronym/ Ref. Ctry Principal DescriptionName No. Investigator

PLEGPAY 16 I A. Matucci Plasma contactor electron gunFIPEX 47 D S. Fasoulas Gas sensor for atomic-oxygen flux

51 ESA M. v. Eesbeck Effect of space exposure of materials on thermo-optical and mechanical properties54 F J.C. Mandeville Monitoring and detection of micrometeoroids and space debris55 F A. Paillous Calorimetric/dynamic measurement of thermo-optical property degradation56 ESA M. v. Eesbeck Effects of contamination/radiation on optical surfaces57 UK A.R. Chambers Atomic-oxygen experiment58 D B. Schaefer Manipulator system identification and dynamic model validation59 I P.G. Magnani Intelligent axis for A & R60 I E. Re Tactile sensor-based robot control

DEBIE 62 ESA G. Drolshagen Active meteoroid/debris impact detector64 NL C. Heemskerk Robot inspection and measurement of LEO environment on solar cells66 NL W. Jongkind Teleoperated intelligent gripper for handling tasks68 UK R.A. Rowntree Tribology laboratory for bearing cage stability/wear and loss of fluid lubricants testing

CREEP 81 E. Daly & Columbus Radiation Environment and Effects PackageA. Zehnder

HTSC 18 D M. Klanda High-Temperature-Superconductor DemonstratorHEPTES 88 D S. Krause Heat-Pipe/Thermal-Energy-Storage Receiver Element

Table 2. EXPOSE characteristics

Pointing requirements Expose requires zenith orientation and solar pointing

Pointing Coarse Pointing Device

Sample exposure variable control Motorised lids/shutters

EXPOSE features:Sample containers 12

Selectable open/close lids 8Permanently open 4

Atmosphere Vacuum or inert gasTemperature control Heating (only)Sensors UV, radiation, temperature and pressureActive signals Real-time telemetry

EXPOSE

SPORT

microwave background radiation would be ofgreat interest for modern cosmology.

4. FOCUS – Intelligent Fire Detection InfraredSensor System (Fig. 7)FOCUS will detect, from the ISS orbit, andanalyse high-temperature events such asvegetation fires and volcanic eruptions. Largeforest and savannah fires, as well as volcanicactivities, have global atmosphericconsequences (e.g. greenhouse effect, cloudgeneration, climate change) and themeasurements onboard the Station willcontribute to the classification, atmosphericcomposition determination and geocoding ofthe data, which will be transmitted to aworldwide scientific, application-oriented andpre-operational user community.

The Principal Investigator for FOCUS is Prof. H.P. Röser from the DLR Institute fürWeltraumsensorik, in Berlin (D). Furtherimportant contributions are being made byvarious institutes in Spain, Italy, Germany,France, Greece and Russia.

5. SOLAR – A Solar Monitoring Observatory(Fig. 8)The main objective of this experiment is tomeasure the solar spectral irradiance withunprecedented accuracy. Apart from thescientific contributions for solar and stellarphysics, knowledge of the ‘solar constant’ andits variations is of great importance foratmospheric modelling, atmospheric chemistryand climatology.

The SOLAR observatory consists of threeinstruments, which complement each other

and together cover the wavelength range 17 - 3000 nm in which 99% of solar energy isradiated. They are:

– SOVIM (Solar Variable & Irradiance Monitor):The Principal Investigator is Prof. C. Fröhlichfrom the World Radiation Centre in Davos(CH), who has teamed up with several co-investigators from Belgium, France, ESTEC, Switzerland and the USA. A similarinstrument (SOVA) has already been flownon ESA’s Eureca retrievable carrier.

– SOLSPEC (Solar Spectral Irradiance Measure-ments): The Principal Investigator is Dr. G. Thuilllier from the Serviced’Aeronomie/CNRS, Verrières le Buisson (F).The co-investigators come from Belgium,France, Germany, Switzerland, the UnitedKingdom, the USA and Switzerland.SOLSPEC has already been flown onvarious Spacelab missions and on Eureca.

– SOL-ACES (Solar Auto-Calibrating EUV/UV Spectrophotometers): The PrincipalInvestigator is Dr. G. Schmidtke from theFraunhofer Institut für PhysikalischeMesstechnik in Freiburg (D), with co-investigators from Germany and the USA.SOL-ACES is a new instrument that is stillto be developed and covers the solarspectral irradiance range from 17 to 220 nm.

The three instruments are mounted on a CoarsePointing Device, which provides Sun-pointingfor about 13 minutes per orbit.

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Figure 7. FOCUS will detectterrestrial high-temperature

events such as vegetationfires

Figure 8. The SolarMonitoring Observatory

(SOLAR) will measure theSun’s total and spectral

radiance

Figure 9. The overallschedule for ESA’s ExpressPallet Project

Figure 10. The GlobalTransmission Services(GTS) system, which willbroadcast data and high-accuracy time signals

ESA’s use of the Russian SegmentThe Russian Segment of ISS is an attractiveplace to fly external payloads, and twoEuropean payloads are already selected, the‘Global Transmission Services System’ (Fig. 10)and ‘Matroshka’ (Fig. 11a, b).

The Global Transmission Services (GTS)SystemAs a continuation of the recent successfulcooperation between ESA and Russia on theMir station, both sides have agreed to

Overall schedule for ESA’s Express Palletproject As can be seen in Figure 9, approximately oneyear elapsed between the issuing of theAnnouncement of Opportunity and theselection of a feasible payload complement.Last year (1998) was used mainly foraccommodation analyses for the five differentadapters. The main development effort (Phase-C/D) is due to start in May 1999, in order tomeet the projected Shuttle launch dates forUF3/4 at the end of 2002.

european external payloads selected

implement GTS as a Euromir-E replacementactivity. GTS is a relatively small payload thatwill transmit highly accurate time and codeddata signals for dedicated receivers on theground.

The GTS experiment uses a transmitteraccommodated onboard the ISS for signaldistribution via an externally mounted antenna(with a transmission cone half-angle of approx.70 deg) on the Russian Service Module. Thesignals transmitted – at two dedicatedfrequencies in the 400 MHz and 1.4GHz ranges– can be received for 5 -12 min several timesper day by ground receivers with sufficientsensitivity.

The same services – specifically the highlyaccurate time signal – will be available throughdedicated connections to users accom-modated on-board the Russian Segment.Applications foreseen include:– accurate time receipt and automated local

time conversion for mobile users on theground (e.g. wrist watches)

– car theft-protection (electronic car keys)– coding and re-coding of electronic cards

(chip cards, smart cards, credit cards).

The GTS experiment, which will beginoperating approximately six months afterlaunch of the Russian Service Module, will lastat least two years.

The Matroshka payloadThe Matroshka experiment (Fig. 11) aims tomeasure the radiation that an astronaut facesduring Extra Vehicular Activity (EVA).Knowledge of the radiation doses to whichsensitive body organs are exposed during longEVAs is an important prerequisite for radiationrisk assessment.

The Matroshka payload consists of a humantorso/head dummy, composed of varioustissue substitutes simulating the human body interms of size, shape, orientation, mass densityand nuclear interactions. At the sites of thebody organs of interest, spaces are provided atthe surface and at different depths within the phantom to accommodate dosimeterpackages to measure any ionising radiationreceived.

The key milestones for the Matroshka projectare currently:– launch with Progress 268 in mid-2002– external operation on the Russian Service

Module from mid-2002 (installation duringEVA No. 37) to mid-2003 (retrieval duringEVA No. 47)

– sample return with the eighth Soyuz flight tothe ISS.

The data gathered will be used to reduceuncertainties in risk estimates for radiation-induced cancer, and for the refinement of theshielding needs for transport facilities for futurelong-duration missions. They also haveimportant implications for ISS crew health andfor mission planning, and thereby contribute tothe ISS environmental monitoring effort.

The AMS Experiment A further important external payload, selectedby NASA, but with an important Europeanscientific contribution, is the Alpha MagneticSpectrometer (AMS) experiment (Fig. 12). Thispayload is designed for the study of antimatterand missing matter. To be located on an ISSExpress Pallet in a zenith-pointing position, theAMS is an international collaboration betweenChina, Finland, Germany, Italy, Russia,Switzerland, Taiwan and the United States. Theteam is led by Nobel Prize winner Prof. S.C.Ting.

The key scientific objective is to search forantimatter, basically anti-helium and anti-carbon, with a detector sensitivity 10

4to 10

5

times better than current limits. The Big Bang

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Figure 11a. Matroshka willbe mounted on the outside

of the Russian ServiceModule

Figure 11b. Mathematicalmodel of the Matroshka

human torso/head dummy

Figure 12. The detectorarrangement for the AlphaMagnetic Spectometer(AMS), designed tomeasure anti-matterparticles

year. A wide range of first-class science andearth-observation studies, industrial space-technology tests and the provision of newservices can be achieved using the ISS externalsites. As the quality of the more than onehundred responses received to the Announce-ment of Opportunity has amply demonstrated,the European research community andEuropean aerospace industries are more than ready to exploit these new opportunities that the International Space Station will provide. r

theory of the origin of the Universe requiresmatter and antimatter to be equally abundantat the very hot beginning. The AMS payload isexpected to detect a few anti-carbon nuclei perweek if the present theory of the Big Bang iscorrect.

ConclusionESA is committed to fly the payloads that havebeen selected on the external sites of the ISS towhich it has negotiated access. Detailedaccommodation analyses have been carriedout and the implementation phase will start this

european external payloads selected