SMART-1 by Sun Power to the Moon June 2002

8/7/2019 SMART-1 by Sun Power to the Moon June 2002

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BR-191June 2002

By Sun power to the Moon


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Cluster, which is a four-spacecraft mission to investigate inunprecedented detail the interaction between the Sun and theEarths magnetosphere.

Giotto, which took the first close-up pictures of a cometnucleus (Halley) and completed flybys of Comets Halley andGrigg-Skjellerup.

Hipparcos, which fixed the positions of the stars far moreaccurately than ever before and changed astronomers ideasabout the scale of the Universe.

Hubble Space Telescope, a collaboration withNASA on the worlds most important and successful orbitalobservatory.

Huygens, a probe to land on the mysterious surface ofSaturns largest moon, Titan, in 2004. Part of the internationalCassini mission.

ISO, which studied cool gas clouds and planetaryatmospheres. Everywhere it looked, it found water insurprising abundance.

IUE, the first space observatory ever launched, marked thereal beginning of ultraviolet astronomy.

SOHO, which is providing new views of the Sunsatmosphere and interior, revealing solar tornadoes and theprobable cause of the supersonic solar wind.

Ulysses, the first spacecraft to fly over the Suns poles.

XMM-Newton, with its powerful mirrors, is helping tosolve many cosmic mysteries of the violent X-ray Universe,from enigmatic black holes to the formation of the galaxies.

About ESA

The European Space Agency (ESA) was formed on 31 May 1975. It currently has 15 Member States: Austria, Belgium,Denmark, Finland, France, Germany, Ireland, Italy, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and theUnited Kingdom. Canada is also a partner in some of the ESA programmes.

The ESA Science Programme has launched a series of innovative and successful missions.Highlights of the programme include:

For further information on the ESA Science Programme please contact the Science ProgrammeCommunication Service on (tel.) + 31 71 565 3223; (fax) + 31 71 565 4101

More information can also be obtained via the ESA Science Website at: http://sci.esa.int

Prepared by: Science Programme Communication ServiceText by: Nigel CalderPublished by: ESA Publications Division

ESTEC, PO BOX 2992200 AG NoordwijkThe Netherlands

Editors: Bruce Battrick and Monica TaleviDesign and layout: AOES Medialab & Carel HaakmanCopyright: (c) 2002 European Space AgencyISSN No. : 92-9092-750-XISBN No.: 0250-1589Price: 7 EurosPrinted in the Netherlands


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Contents

By Sun power to the MoonWelcome to the double planetThe magic of ion enginesThe SMART way to travel

A spiral pathway to the MoonMasterpieces of miniaturizationWhat will all the instruments do ?

Testing new techniquesEPDP and SPEDEKaTE and RSIS

Laser LinkOBANObserving the Moon and the SunAMIE,SIR and D-CIXSXSMSPEDERSIS

Lunar science still plenty left to do !Peering for ice in the darkest craters

Where did the Moon come from?Lunar science is now a global effort

SMART-1

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How solar energy will take a spacecraft to the Moon

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Illustration by Medialab, ESA 2002


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By Sun power to the Moon

By March 2003 a hitchhiking team of engineers and scientists will be at Europe'sspaceport at Kourou in French Guiana,thumbing a lift for a neat lit tle spacecraft,

ESA's SMART-1,on the next Ariane-5 launcher that has room to spare.

It's not very big, just a box a metre wide with folded solar panels attached. Sixstrong men could lift it.It weighs less than 370 kilos,compared with thousands

of kilos for Ariane's usual satellites.So it should pose no problems as an auxi-liary passenger.

SMART stands for Small Missions for Advanced Research andTechnology. They pave the way for novel and ambitious scienceprojects of the future, by testing the new technologies that will beneeded. But a SMART project is also required to be cheap - about

one-fifth of the cost of a major science mission for ESA - which is whySMART-1 has no launcher of its own.

Its main purpose is to let engineers evaluate a new way of propellingspacecraft on far-ranging space missions. Power from SMART-1's solar

panels will drive an electric propulsion system called an 'ion engine'.Thedemonstration task is to overcome the Earth's gravity and put the space-

craft into orbit around the Moon.

After 40 years of Soviet and American lunar exploration,knowledge of the Moon'ssurface is still surprisingly incomplete.Always ready to seize a chance to make new

discoveries, Europe's space scientists have fitted SMART-1 with very modern andcompact sensors.

A piggyback ride intospace,on Europe's Ariane-5

launcher,wil l put SMART-1into orbit around the

Earth,from whereit will begin a long,slow

journey to the Moon. ESA

As the first spacecraft touse primary electric propulsionin conjunction with gravitymanoeuvres, and as Europes firstmission to the Moon, SMART-1 opensup new horizons in space engineering

and scientific discovery.And wepromise frequent news and pictures,so that everyone can share in ourlunar adventure.

Giuseppe RaccaESAs SMART-1 Project Manager


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Well map lunar minerals in greater detail than ever before using infrared rays.With X-rays,well make the first comprehensive inventory of key chemical elementsin the lunar surface.Add to this many scenes from our advanced multi-colourcamera, and SMART-1 will renew our view of the Moon.

Bernard FoingESAs SMART-1 Project Scientist

Solar panels of thegallium-arsenide type thatwil l power SMART-1 enabledthe Dutch-buil t solar-poweredcar 'Nuna' to win the WorldSolar Challenge race acrossAustralia in 2001. ESA

The SNECMA PPS-1350 ion enginewil l provide SMART-1's primarypropulsion.The glow comes fromthe accelerated atoms of xenon gas.Illustrat ion by AOESMedialab, ESA 2002

Image compositeby AOES Medialab, ESA 2002


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SMART-1 is Europe's first mission to the Moon.The scientists takingpart have a 21st-Century view of our companion in space,which makes

our connection with it more intimate than ever. The Moon is no longerseen merely as a satellite,but as the Earth's daughter,forming a double planet.

When human beings first went to sea,many thousands of years ago,they monitored the phases and motions ofthe Moon to know the state of the tide in various harbours.More subtle shifts,up and down the sky, fascinatedprehistoric experts who wanted to predict eclipses. Computing the first Full Moon after the spring equinoxdefined Easter in the Christian calendar.And before modern lighting, convenors of meetings chose dates withpredictable moonlight, to help participants on their way.

Such ancient technical interest in the Moon never conflicted with the admiration for its beauty, from paganworshippers of Diana the Huntress to writers of modern pop songs.Nor need it do so now.The fact that human

beings have walked on the Moon,and will again,should not diminish but enhance the sense of wonder. In themodern perspective, seeking a lunar foothold for science and technology could be a natural step afterestablishing bases in the harsh but splendid landscapes of Antarctica.

Beauty and science go hand in hand.The artist Leonardo da Vinci was perhaps the first to figure out 500 yearsago that the subtle glow on the dark part of a crescent Moon is due to light from the Earth.Now astronomersand space scientists measure that earthshine to gauge variations in our planet's cloudiness, and the role of

clouds in climate change.

The Moon is almost as wide as the planet Mercury,and27 percent of the width of the Earth. Compared withits planet,it is relatively far larger than any other moonin the Solar System.Our neighbour Mars has two smallmoons, and Venus none at all. The geology of thoseplanets is totally different from ours. So it is notfar-fetched to ask whether the Moon's existence givesthe Earth qualit ies especially suited to life.

A shocking birth for the Moon?

SMART-1's researchers will checkthe theory that our companion inspace was made from the debrisof a monstrous collision bill ionsof years ago - between the newlyborn Earth and a smaller planet.Illustrat ion by AOESMedialab, ESA 2002

Welcome to the double planet


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By the middle of this century theMoon is likely to be a mannedbase,not only for science but for

mining and engineering too - anda way-station for more distantspaceflight.Image courtesy Pat Rawlings/SAIC/NASA JSC -

-Mark Dowman and Mike Stovall/Eagle Engineering,Inc. / NASA JSC --

Clementine/ BMDO/NSSDC --LunaCorp/Robot ics Instit ute

According to a leading theory, the Moon was formed by a collision with a huge object when the Earth wasvery young. SMART-1 will investigate this idea.The spacecraft will also examine the craters of the Moon that

chronicle a prolonged bombardment of the double planet by comets and asteroids. There is a particu-larly large basin near the Moon's South Pole,which SMART-1 will scrutinize.Our own planet suffered even moreseverely from such impacts.

Earth and Moon have shared a common history for 4.5 million years.Knowing the Moon more thoroughly willhelp scientists to understand our home in space.Then we may be better able to safeguard it .

The Earth-Moon system isplainly a double planet when

seen from far out in space.Illustrat ion by AOESMedialab, ESA 2002


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The magic of ion engines

Operating in the near vacuum of space, ion engines shoot out a propellant gas much faster than the jet of achemical rocket.They deliver about ten times as much thrust per kilo of propellant used.The ions that give the

engines their name are charged atoms,accelerated by a choice of electric guns. If the power comes from thespacecraft's solar panels,the technique is called solar-electric propulsion.

Ion engines work their magic in a leisurely way.As solar panels of a normal size supply only a few kilowatts ofpower, a solar-powered ion engine cannot compete with the whoosh of a chemical rocket. But a typicalchemical rocket burns for only a few minutes.An ion engine can go on pushing gently for months or even years- for as long as the Sun shines and the small supply of propellant lasts.

The ion tortoise eventually overtakes the chemical hare,and continues accelerating, slashing the time for inter-planetary flight.But so far,that is only a theory.

How an ion engine works.Electrons att racted into the discharge chamber collide with xenon atoms from thepropellant gas supply, making charged atoms (ions). Current-carrying coils, inside and outside thedoughnut -shaped discharge chamber,sustain a magnetic field oriented like the spokes of a wheel. By the Halleffect,ions and electrons swerving in opposite directions in the magnetic field create an electric field.This expelsthe xenon ions in a propulsive jet. Other emitted electrons then neutralize the xenon, producing the blue jet.Illustrat ion by AOESMedialab, ESA 2002


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ESA's Artemis was saved fromthe grave by its ion engines.

After its launch in 2001 put thisexperimental telecommunications

satellite into too low an orbit,ion engines intended only formanoeuvring have graduallyraised the orbit . ESA/J.Huart

BepiColombo (left) and the Solar Orbiter are ESA's first long-range sciencemissions designated to use ion engines. ESA

An ion engine can slash almost four years off the time that BepiColombo will take toget to Mercury.But we need hands-on experience with SMART-1 to be confident aboutusing this new technology.

Gordon WhitcombESAs Head of Future Science Projects

By Sun power towards the Sun

SMART-1 will ensure Europe's competence in the use ofelectric propulsion, and its independence in this 21stCentury space technology

BepiColombo, ESA's future mission to the innermost

planet Mercury,near to the Sun,will use ion engines tospeed it on its way.

The Solar Orbiter,which will swoop even closer to theSun for close-up views, will use the same type of iondrive as BepiColombo.

Other space science missions are expected to use ionengines for complex manoeuvres in the vicinity of theEarth's orbit, including LISA,a mission that will detectgravitational waves coming from the distant Universe.

In 1998, NASA launched a demonstration spacecraftcalled Deep Space 1,which flew by a near-Earth asteroid

and went on to intercept a comet.ESA's SMART-1,withmuch less chemical boost, will go no farther than theMoon.But it will demonstrate more subtle operations ofthe kind needed for distant missions.These will combinesolar-electric propulsion with manoeuvres using thegravity of planets and moons.

The SMART-1 ion enginebeing test fired. ESA


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The SMART way to travel

The type of ion engine chosen for SMART-1 makes clever use of an effect discoveredby the American physicist E.H. Hall in 1879, whereby a current flowing across a

magnetic field creates an electric field directed sideways to the current.This is usedto accelerate ions (charged atoms) of xenon. A gassy element with atoms about131 times heavier than hydrogen atoms,xenon is chemically inert.

Drawing electric power of 1350 watts from SMART-1's solar panels, the ion enginegenerates a thrust of 0.07 newton.That is equivalent to the weight of a postcard.

By accelerating SMART-1 at 0.2 millimetres per second per second, the incrediblygentle thrust could in theory fling the spacecraft right out of the Solar System,if sus-tained for long enough.In practice,SMART-1 will use its ion engine intermittentlyover 16 months, fighting against the Earth's att raction, to put itself into orbit

around the Moon.

For the first 2 or 3 months, the leisurely journey brings problems due to SMART-1'sexposure to possible harm from energetic atomic particles in the radiation beltsthat surround the Earth. The electronics and instruments have been hardenedto resist such damage.

SMART-1 first orbits the Earthin ever-increasing ellipses. When

it reaches the Moon, its orbitis altered by the Moons gravita-tional field.It uses a number of

these gravitational assistst oposition itself for entering orbit

around the Moon.Illustrat ion by AOESMedialab, ESA 2002


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The Ariane-5 launcher will put SMART-1 into anelliptical orbit around the Earth. Under the control of

the European Space Operations Centre (ESOC) inDarmstadt, Germany, on two days per week, repeatedburns of the ion engine will change the ellipse into acircle and gradually expand it in a spiral.

Month by month the Moon revolves around its ownorbit,350 000 to 400 000 kilometres from the Earth.AsSMART-1 gains distance from the Earth, its speed willslacken.When 200 000 kilometres out, the spacecraftwill begin to feel significant gravitational tugs fromthe Moon as it passes by.

Mission controllers must then inaugurate a new era ofspace navigation.For the very first time,they will use thesustained thrust of electrical propulsion jointly withmanoeuvres under gravity.Isaac Newton knew nothingof such tricks,and ESA's experts have had to invent freshmathematics for figuring out the best orbits.

The tug of the Moon's gravity will at first help to widen the spiral orbit,in regular encounters called lunar resonances.By the time SMART-1 passes within 60 000 kilometres of the Moon, the effect of gravity will be much more pro-nounced,in encounters known as lunar swingbys.

At a crucial stage in the journey, called lunar capture,SMART-1 will pass through an invisible doorway in spaceat Lagrange Point No.1,or L1 for short.As first noted bythe mathematician Joseph-Louis Lagrange in 1772, thegravitational effects of the Moon and the Earth are inbalance at L1,50 000 to 60 000 kilometres out from theMoon on the earthward side.

Beyond L1, SMART-1 will fly over the lunar north pole,aiming at a point of closest approach above the southpole, so achieving a wide polar orbit around the

Moon.During the weeks that follow its capture by theMoon, SMART-1's ion engine will gradually reducethe size and duration of this orbit, to improve its viewof the lunar surface.

A spiral pathway to the Moon

Joseph-Louis Lagrangediscovered by mathematics

the strange regions ofgravitational equilibrium

now called 'Lagrange Points',through one of which

SMART-1 must t ravel. Bornin Turin in 1736,he worked

in Berlin and in Paris,where he died in 1813.

Once SMART-1 has beencaptured by the Moons gravity,it begins to work its way closerto the lunar surface.Illustrat ion by AOESMedialab, ESA 2002


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The SMART-1 spacecraft spans 14 metres with its solar panels extended,but otherwiseeverything for propulsion, communications, housekeeping and instrumentation fits

into a cube just 1 metre across.

Propulsion by an ion engine is not the only innovative technology on SMART-1.Itssolar panels use an advanced type of gallium-arsenide solar cell in preference to thetraditional silicon cells.And it will test new communications and navigational tech-niques.

Out of a total mass at launch of 370 kilograms, the payload available for a dozentechnological and scientific investigations is 19 kilos.Like other components of the

spacecraft, the scientific instruments use state-of-the-art concepts and methods ofminiaturization to save space and economize on mass.For example the X-ray telescope

D-CIXS makes a cube just 15 centimetres wide and weighs less than 5 kilos.

Masterpieces of miniaturization

Building aspacecraft forESA means fittingtogether many piecescoming from differentcountries. Luckily thecross-border teamworkis magnificent.

Peter RathsmanSwedish SpaceCorporation,PrimeContractor forSMART-1

SMART-1 is packed into its stowedconfiguration,as it will be for launch.

One set of solar panels is deployedfor testing. Supports hold the panels

from above to simulate zero-gravity.

Building SMART-1 has involvedalmost thirty industrial

contractors from eleven Europeancountries and the United States.Illustrat ion by AOESMedialab, ESA 2002

ESA

ESA


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Purpose

Spacecraft

Scientific Payload

Launch

Orbit

Ground Stations

Mission Lifetime

Prime Contractor

Flight testing electric propulsion and other deep-space technologies, while performingscientific observations of the Moon.

One cubic metre,370 kg. Solar panels span 14 metres when deployed and provide1.9 kW of power.

19 kg.

March 2003 from Kourou,French Guiana on a shared Ariane-5 ride to geostationary transfer orbit (GTO).

16-month transfer orbit from GTO to lunar orbit insertion, then polar elliptical operational orbit,ranging from 300 km to 10 000 km in altitude above the Moon.

ESA network stations around the world,operating for 8 hours twice a week.

2 - 2.5 years.

Swedish Space Corporation, Solna, Sweden

1 SIR

2 Sun sensors

3 SPEDE boom

4 AMIE camera

5 D-CIXS

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Fuel tank for attitude control

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Star tracker

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Motor to turn solar array

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Communication transponders

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Ion engine control electronics

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Attitude control thrusters8

7 EPDP sensors

6 Communication antenna

Ion engine with orientationmechanism (to maintain thrusterpointing as fuel tanks drain)

1

2

4

5

2

3

6

7

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9 10

11

12

13

13

13

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Illustrat ion by AOESMedialab, ESA 2002


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What will all the instruments do?

Testing new techniques

EPDP and SPEDE.Designers of future solar-electric spacecraft want to know howSMART-1's ion engine performs,what side-effects it has,and whether the spacecraftinteracts with natural electric and magnetic phenomena in the space around it.Possible problems include deflection of the ion engine's thrust direction,erosion ofsurfaces,short-circuits by sparks, interference with radio signals,and accumulatingdust.The main onboard instruments monitoring these effects are EPDP and SPEDE.

KaTE and RSIS.Small changes in SMART-1's motion will reveal the precise thrustdelivered by the ion engine.Like police radars used to catch speeding motorists,RSIS will employ the Doppler effect, to see how the speed alters the wavelength ofradio pulses.It will use the very short radio waves of KaTE.The primary purpose ofKaTE is to demonstrate the next generation of radio links between the Earth andfar-flung spacecraft. Microwaves in the Ka band, around 9 millimetres in wave-length, can be focused into relatively narrow beams by the small dish antennasavailable on the spacecraft.

Laser Link is another communications experiment.ESA already has laser links with

telecommunications satellites from an optical ground station on Tenerife in Spain'sCanary Islands.Aiming the beam becomes much more difficult if, like SMART-1,thespacecraft is far away and moving rapidly.The hope isthat the onboard camera AMIE will see Tenerife aglowwith laser light.

OBAN. Future spacecraft will be more self-reliant inguiding themselves along pre-defined paths towardsdistant destinations.OBAN is to evaluate a computertechnique for on-board autonomous navigation. Itwill use the bearings of stars seen by SMART-1's startrackers, and the Earth, Moon and possibly asteroidsseen by the AMIE camera.

Multinational teams of scientists and engineers will conduct ten different investigations coordinated by aScience and Technology Operations Centre. The instrument teams are led by Principal Investigators from

Finland,Germany,Italy,Switzerland and the United Kingdom.All ESA member countries are taking part,provid-ing Co-Investigators for various experiments.

How three remote-sensing instruments on SMART-1 will scan the Moon'ssurface during one pass.Repeated passes will gradually fill in the picture.

Illustrat ion by AOESMedialab, ESA 2002

Weighing no more than anamateur's camera,AMIE wil l send

back electronic images of theEarth and Moon - and watch for

laser signals from the Earth. ESA


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Observing the Moon and the Sun

AMIE, SIR and D-CIXS. Different kinds of visibleand invisible light coming from the lunar surface willprovide clues about its chemical composition andgeological history.The ultra-compact electronic cam-era, AMIE, will survey the terrain in visible andnear-infrared light. An infrared spectrometer, SIR,will chart the Moon's minerals. An X-ray telescope,D-CIXS, will identify key chemical elements in thelunar surface.The major scientific goals are describedin the following pages.

XSM. The D-CIXS measurements could be confusedby variations in solar X-ray emissions,which dependon how stormy the Sun is at the time. So SMART-1monitors the solar X-rays with its XSM instrument.XSM will also make its own independent study ofsolar variability.

SPEDE. Like a ship at sea, the Moon leaves a wakein the solar wind - the non-stop stream of chargedparticles and associated magnetic fields coming fromthe Sun.The SPEDE electrical experiment will observe

this effect at close quarters.

RSIS.With help from the KaTE microwave system andthe AMIE camera, the RSIS radio experiment willdemonstrate a new way of gauging the rotations ofplanets and their moons.It should be able to detect awell-known nodding of the Moon,which slightly t iltsfirst its north pole and then its south pole towards theEarth.

Instruments and techniques to be tested in exami-ning the Moon from SMART-1 will later help ESA's

BepiColombo spacecraft to investigate the planetMercury.

The feasibili ty of using a laser beam for communicating with a distantspacecraft wil l be tested by Laser Link from Tenerife to SMART-1.Illustrat ion by AOESMedialab, ESA 2002

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How does the electric sea in the Earth's space environment interact with an electric engine? Can it harm thespacecraft? EPDP and SPEDE will find out . Illustrat ion by AOESMedialab, ESA 2002


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Lunar science _ still plenty left todo !

The Moon's pockmarked face gives an impression of what the Earth looked like around 4 bill ion years ago,whencomets and asteroids rained on the newly formed planets of the Solar System,creating craters both large and

small. The Earth's wounds have mostly healed, but the Moon has scarcely changed since 3.5 bill ion years ago,when molten lava made the flat,dark features called maria.

From their six landings during NASA's Apollo Programme (1969-1972),astronauts brought rock samples homefor analysis in the world's laboratories.Three unmanned Soviet spacecraft also recovered Moon rocks. Scientistsprized them as samples of the primordial minerals that went into building the Moon and the Earth,and as chron-iclers of impacts.But these samples mostly represent the near-side equatorial region.The far side of the Moonand polar regions,which have a quite different geological history,were not included.

Two small American spacecraft,Clementine and Lunar Prospector,went into orbit around the Moon in 1994 and1998,carrying a variety of remote-sensing instruments to explore the whole lunar surface.Lunar Prospector also

mapped the Moon's gravity and discovered magnetic regions.But many unanswered questions still perplex thelunar scientists.

SMART-1's camera AMIE will enable scientists to study afresh the Moon's topography and surface texture. Itmeasures visible light at a million points in a field of view 5 degrees wide,and filters can select yellow light,redlight or very short infrared rays.By looking at selected regions from different angles,and under different light-ing condit ions,AMIE will provide new clues as to how the lunar surface has evolved.

With longer infrared rays, the infrared spectrometer SIR will map the surface distribution of minerals such aspyroxenes,olivines and feldspars,in far more detail than Clementine did when it scanned the lunar surface at sixdifferent infrared bands.SIR distinguishes about 256 wavelength bands,from 0.9 to 2.4 microns.The mineralogy

will reveal the effects of cratering and maria formation, and the nature of subsurface layers exposed by fracturesin the Moon's crust.

How SIR on SMART-1 will mapthe minerals of the Moon.Materials that often look

merely grey in visible light aremore colourful in the infrared.

When seen in the form of aspectrum,showing relativeintensities at different infrared

wavelengths,each mineral has adistinctive signature depending

on which wavelengths it absorbsmost strongly. Courtesy of NASA/JPL.


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Peering for ice in the darkest craters

Any water on the lunar surface would be very helpful in the creation of permanentbases on the Moon.But to have survived, the water must be in the form of ice inplaces always hidden from the Sun, where the temperature never rises aboveminus 170oC.Such dark places exist,notably in the bottoms of small craters in thepolar regions.

The trickiest task that the SMART-1 scientists have set themselves is to peer into thedarkness with SIR, looking for the infrared signature of water ice - and perhaps offrozen carbon dioxide and carbon monoxide too.By definition,no direct light fallsin the target areas. But rays from nearby crater rims, catching the sunshine,maylight the ice sufficiently for SIR to see it, when data from many passes are added

together.

We took a commercially available instrument and adapted it for exploring otherworlds.If it works as well as we expect at the Moon,small and lightweight instrumentslike SIR will become the norm for using infrared light to discover the composition ofplanets, asteroids and comets.

Uwe KellerGermany's Max-Planck-Institut fr Aeronomie,Team Leader for SIR.

The Moons south pole is ofgreater scientific interest thanthe north because the area thatremains in shadow is much larger.Clementine, BMDO,NRL,LLNL

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CourtesyNASA/JPL Near the Moon's south pole isthe South Pole - Aitken Basin, thelargest known impact crater in

the entire Solar System.Colouredblue in this topographic map,it is

2500 kilometres wide and up to12 kilometres deep. NASA


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Where did the Moon come from?

The Moon is a key witness of the early conditionswhen life emerged on our planet. As the daughter ofthe Earth,she holds keys for understanding our originsand for preparing for the future exploration of theSolar System.

Bernard FoingESAs SMART-1 Project Scientist

If this scenario of the Moon'sorigin is correct,iron should berelatively scarce in the lunarsurface,compared withmagnesium, for example.D-CIXS will be able to judge theproportions.Illustrat ions by AOESMedialab, ESA 2002

The fashionable theory is that the Moon is the resultof a collision during the birth of the Solar System4500 million years ago.When the Earth was nearlycomplete,a gigantic wandering asteroid the size ofMars supposedly collided with our planet, flingingvaporized rock and debris from both bodies intospace.Some of it went into orbit around the Earth,and congealed to make the Moon.

The impact would have greatly altered the outerlayers of the Earth too. So fuller understanding ofboth the Earth and the Moon depends crucially onconfirming or refuting this theory.


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If the story is right, then the Moon should contain less iron than the Earth, in pro-portion to lighter elements such as magnesium and aluminium.By gauging the rel-ative amounts of chemical elements comprehensively for the very first time,SMART-1 can make a distinctive contribution to thismomentous scientific issue.

D-CIXS (pronounced dee-kicks) is the instrument forthe job. X-rays from the Sun cause atoms in the lunar

surface to fluoresce,emitting X-rays of their own.Theprecise energy carried by each X-ray is a signature ofthe element emitt ing it.

Lunar science is now a global effort

The International Lunar Exploration Working Groupunites ESA, ISAS and NASDA (Japan), NASA andseveral other space agencies around the world. Itaims to put together results from all of the recentand future spacecraft , in integrated data sets.

Interpretations of lunar geology and history will beaided by Japans Lunar-A spacecraft (2003). It wil ldrop instruments onto the Moons near and farsides, to measure heat flow and to look for theMoons core by studying moonquake waves.Japanis also preparing Selene (2004) to continue the re-examination of the lunar surface by remote sensing,started by the US Clementine and Lunar Prospectorspacecraft , and by Europes SMART-1. Poolingresults will enhance the scientific value of all themissions,including SMART-1.

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Surprisingly, no one has yet made the observationsthat we plan. Thats why our small instrument on thesmall SMART-1 spacecraft has the chance to make a

big contribution to understanding the Moon and itsrelation to the Earth.

Manuel GrandeUKs Rutherford Appleton Laboratory,D-CIXS team leader

Elements were charted on theMoon by NASA's Clementine

spacecraft.D-CIXS on SMART-1will make similar but more

detailed and more comprehen-sive maps,using X-rays.

Image edit by AOESMedialab, ESA 2002.Original image courtesy of NASA

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SMART-1 by Sun Power to the Moon June 2002

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