Low Energy Neutral Atom Imaging on the Moon With SARA Aboard Chandrayaan-1 Mission

8/8/2019 Low Energy Neutral Atom Imaging on the Moon With SARA Aboard Chandrayaan-1 Mission

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Low energy neutral atom imaging on the Moon withthe SARA instrument aboard Chandrayaan-1 mission

Anil Bhardwaj1,, Stas Barabash2, Yoshifumi Futaana2, Yoichi Kazama2,Kazushi Asamura3, David McCann2, R Sridharan1, Mats Holmstrom2,5,

P eter W u rz4 and Rickard Lundin2

1Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum 695 022, India.e-mail: [email protected]

2Swedish Institute of Space Physics, Box 812, 98128, Kiruna, Sweden.3Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 2298510, Japan.

4Physikalisches Institut, University of Bern, CH-3012 Bern, Switzerland.5Currently at NASA Goddard Space Flight Center, Mail Code 612.2, Greenbelt, MD 20771, USA.

This paper reports on the Sub-keV Atom Reflecting Analyzer (SARA) experiment that will beflown on the first Indian lunar mission Chandrayaan-1. The SARA is a low energy neutral atom(LENA) imaging mass spectrometer, which will perform remote sensing of the lunar surface via

detection of neutral atoms in the energy range from 10 eV to 3 keV from a 100 km polar orbit. Inthis report we present the basic design of the SARA experiment and discuss various scientific issuesthat will be addressed. The SARA instrument consists of three major subsystems: a LENA sensor(CENA), a solar wind monitor (SWIM), and a digital processing unit (DPU). SARA will be usedto image the solar windsurface interaction to study primarily the surface composition and surfacemagnetic anomalies and associated mini-magnetospheres. Studies of lunar exosphere sources andspace weathering on the Moon will also be attempted. SARA is the first LENA imaging massspectrometer of its kind to be flown on a space mission. A replica of SARA is planned to fly toMercury onboard the BepiColombo mission.

1. Introduction

A planetary exploration program has been ini-tiated by India with a mission to the Moon the Chandrayaan-1 mission (Bhandari 2004;Thyagarajan and Annadurai 2004; Adimurthy andRamanan 2004; Goswami 2005). Chandrayaan isa Sanskrit word made by combing two words,Chandra + Yaan, which mean Moon + craft (orvehicle), that is lunar spacecraft. Chandrayaan-1will be launched in end 2007 and is expected to

have a lifetime of 2 years. The spacecraft will beplaced in a 100 km circular polar orbit. One of theexperiments to fly on this mission will be the SARA(Sub-keV Atom Reflecting Analyzer) instrument.The SARA experiment is a joint collaborative

research program among India, Sweden, Japan,and Switzerland for the exploration of the Moon.In this paper we describe the SARA experimentthat will use LENA (low energy neutral atom) asa diagnostic tool to do remote sensing in the lunarenvironment, and discuss the scientific objectivesof this experiment.

1.1 LENA

The low energy neutral atoms (LENAs) are defined

as energetic neutral atoms that have energies in therange 10 eV to about a few keV. LENAs are notbound by the gravitation force of a planetary body,because they move with a velocity much greaterthan the escape velocity of 2.38 kms1, and being

Keywords. Moon, Moonsolar wind interaction; lunar elemental composition; lunar magnetic anomalies; Energetic NeutralAtom (ENA); lunar mission.

J. Earth Syst. Sci. 114, No. 6, December 2005, pp. 749760 Printed in India. 749


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750 Anil Bhardwaj et al

Figure 1. Schematic diagram showing various mechanismsthat can produce neutral atoms (LENA) on the Moon.

neutral, are not affected by the electromagneticforces. The LENAs thus propagate straight, simi-lar to a photon, and can be used to diagnose andimage target and parent population and to learnabout processes involved. The SARA experimentwill sense LENAs in the energy range of 10 to

3000 eV.

1.2 Production and imaging ofLENA on the Moon

Since the Moon does not possess a large-scale in-trinsic magnetic field, and thus has no global mag-netosphere, as well as is lacking in any extendedatmosphere, the LENAs in the Moon environ-ment can result from the following processes (cf.figure 1):

surface sputtering by precipitating ions, incident solar photon stimulated desorption

(PSD), also called photon sputtering, micrometeorite impact vaporization, and solar wind backscattering.

The micrometeorite impact produces atomshaving a temperature in the range 20005000 K(Eichorn 1978). Assuming a Maxwellian distribu-tion with an average gas temperature of 4000 K(Wurz and Lammer 2003), the energy of LENAwould be 0.34 eV, which is too low an energy to bedetected by a LENA instrument. Atoms generatedby PSD have an energy spectrum f(E) E(+1),where varies from 0.25 to 0.7 (Johnson et al2002). Thus, atoms produced by PSD have verylow energies (mostly close to the binding energy ofatoms, which is in the range 24 eV), and hencewill not be detected by a LENA instrument whoselow-energy cutoff is 10 eV. However, surface sput-tering by precipitating ions can produce LENAsin the energy range of our interest (Futaana et al2005).

The Moon moves around the Earth at a meanorbital distance of 60 RE (RE is Earth radius), andis mainly located in the undisturbed solar wind,except when the lunar phase angle is


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SARA experiment on Chandrayaan-1 mission 751

Figure 2. Block diagram of the SARA experiment. S/Cmeans spacecraft. The pictures of CENA, SWIM, and DPUare only schematics and are not drawn according to theirreal sizes.

(DPU). Mechanically CENA and SWIM are twodifferent units that are connected to DPU bycables, and only the DPU interfaces with the space-craft (cf. figure 2). The total mass of the SARAexperiment is about 3.5 kg and requires a power ofabout 4 W. All the commands to CENA and SWIMwill be routed through the DPU. The functionsof DPU include CENA and SWIM sensor dataacquisition, data compression and packaging, housekeeping and communicating with the spacecraft.

In the following sections we describe the methodof working of CENA and SWIM sensors and theirimportant characteristics.

2.1 The CENA sensor

The CENA (Chandrayaan LENA) sensor com-prises a unique design optimized for:

very low resource budgets, high geometrical factor and high mass resolution,

wide mass range, low energy particle detection (Emin = 10eV), high signal-to-noise ratio.

The CENA consists of four subsystems, namely,

(1) a charged-particle removal system (ion deflec-tor),

(2) a conversion surface,(3) an energy analysis system (which also performs

efficient photon rejection), and

(4) a detection system that provides the mass(velocity) analysis.

Figure 3 shows a schematic view of the CENA(Kazama et al 2005).

2.2 Principle of LENA detection by CENA

Particles enter the CENA sensor through an elec-trostatic charged particle deflector, which sweepsaway ambient charged particles with energies upto 15 keV by a static electric field. The incom-ing neutral particles are then positively ionized

by being reflected from a conversion surface andthen passed through an electrostatic analyzer of aspecific wave shape that effectively blocks pho-tons (cf. figure 4). The electrostatic analyzer alsoprovides crude energy analysis. The wave designof the electrostatic analyzer is similar to thedesign used in the MTOF (solar wind Mass Time-Of-Flight) sensor of the CELIAS (Charge, Ele-ment, and Isotope Analysis System) instrument(Hovestadt et al 1995) on the SOHO spacecraft,which provides a UV photon rejection factor of2 108.

Since lunar regolith contains elements in signifi-cant amounts up to mass 56 (Fe), CENA must becapable of measuring these elements, i.e., up toFe. This means no carbon foils can be used in thetime-of-flight (TOF) section. To measure the par-ticle velocity (mass) we use the particle reflectiontechnique developed and utilized in the NeutralParticle Detector (NPD) of the ASPERA-3 andASPERA-4 experiments aboard Mars Express andVenus Express missions of European Space Agency(Barabash et al 2004). After emerging from the

electrostatic wave analyzer, the ion is post acceler-ated by a voltage of about 3 keV and impacts ona START surface under a grazing angle of about15. During the impact, kinetic secondary elec-trons are emitted from the START surface. Theincoming particle is reflected towards the STOPMCPs (Micro-channel Plates) where it is detectedand produces a STOP pulse. The secondary elec-trons from the START surfaces are guided to theSTART MCPs and produce a START pulse. TheSTART and STOP timing gives the TOF, and

thus the particle velocity. The mass of the parti-cle is determined by combining the TOF measure-ment and the energy derived from the electrostaticanalyzer.

The START MCP provides the two-dimensionalposition (in radius and azimuth) and the timing ofthe particle reflected on the START surface. Theradial position allows accurate determination of theTOF length, and the azimuthal position providesthe azimuthal angle of the incoming particle. Wehave performed a full particle-tracing calculationto maximize the performance of the instrument; all

major mass groups (H, O, Na, K, and Fe) can beresolved by the CENA sensor (Kazama et al2005).The instantaneous field-of-view (FOV) of CENAis 17 160 and it is always in the nadir viewinggeometry (cf. figure 5). It has seven channels, each


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Figure 3. Schematic flow diagram of the CENA instrument showing the principle of the LENA detection.

Figure 4. The left image is a close-up view of the serations for the UV suppression elements in CENA, and the right is azoom of the left image. The height of the serations is 0.177 mm and the pitch is 0.147 mm. The serated surfaces were coatedwith copper sulfide to increase the UV suppression.

with a FWHM FOV of 925. More details of theCENA are given in Kazama et al (2005). Table 1summarizes the characteristics of the CENA sen-sor. Figure 6 provides view of the FOV of theCENA on the lunar surface.

2.3 The SWIM sensor

The flux of LENAs produced by the sputteringprocess is a function of solar wind flux impacting

the lunar surface. Therefore, it is required to mon-itor the precipitating flux of the solar wind on theMoon. The solar wind monitor (SWIM) will pro-vide measurements of energy-per-charge and num-ber density of precipitating ions causing sputtering,

which are important inputs in making a quantita-tive interpretation of the LENA measurements inthe lunar environment.

Besides monitoring of the solar wind, there areseveral scientific topics related to ions around theMoon that SWIM could investigate. For exam-ple, the lunar-originated ions reflected from thesurface can give important data about the lunarsurface composition (Elphic et al 1991). Directlyconnected with the LENA investigations of the

possible mini-magnetospheres on the Moon (seesections 3.3 and 3.4) would be the measurementsof ion composition in and around these mini-magnetospheres. Such measurements could pro-vide valuable information regarding the interaction


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Figure 5. Field of view of the CENA with respect to space-craft velocity vector and look angle (nadir). CENA is alwayslooking towards the Moon, with its FOV centered aroundnadir.

Table 1. Characteristics of the SARA CENA sensor.

Parameter Value

Energy range 10 eV3.3 keVEnergy resolution, E/E 50%Mass resolution H, O, Na-Mg-group, K-Ca-

group, Fe

Pure geometrical factor 102 cm2 sr eV/eV sectorTotal efficiency 1%Angular resolution, FWHM 9(elevation)25(azimuth)Field of view 17 160

between the anomalies and the solar wind, as wellas studying the existence of ion void regions aroundthe anomalies. Moreover, studying the electro-magnetic environment around the terminator withSWIM will provide useful science. The terminatoris the boundary for photoelectrons, which cause acomplicated environment, and in turn could per-turb the solar wind (especially the solar wind pro-tons) in this region. Studying the disturbed solarwind in this region could make it possible to mapthe potential structures around the terminator.

SWIM is a simple ion mass analyzer optimized toprovide monitoring of the precipitating ions usinglittle spacecraft resources. Mechanically SWIMconsists of two parts: (1) a sensor, and (2) an elec-tronic board that includes high voltage supply andsensor electronics.

Figure 7 shows a 3-dimensional picture of theSWIM sensor. The ion flux arrival angle is analyzedby a two 90 plate electrostatic deflector (scanner)

and the energy by a 128

cylindrical electrostaticanalyzer. The ions exiting the energy analyzer arepost accelerated up to 1 keV energy and are madeto strike a START surface. The ion optic is opti-mized to minimize the spot on the START surface

Figure 6. Field of view of the CENA instrument mapped onthe lunar surface. The green bands show the full 160 FOVof the CENA instrument, while magenta and blue colouredbands show the portion of the FOV which is within thesphere of the lunar surface.

Figure 7. Three-dimensional view of the SARA SWIMinstrument. All the major elements of the instrument arelabeled. Dimensions are in mm.

and provide a shallow (15) incident angle toincrease the secondary ion yield and reflection effi-ciency. The START surface is a specially preparedmultilayer surface optimized for

high secondary electron yield, high particle reflection efficiency, and large UV photon absorption.

During impact the incident ion produces sec-ondary electrons and it is reflected towards a STOP

surface. The generated electrons are collected by achannel electron multiplier and they in turn pro-duce a START pulse. The STOP surface is opti-mized for the high secondary electron yield and ahigh UV absorption. Secondary electrons generated


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Solar Wind Flux at Lunar Surface

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10Field of views mapped on the Moon's surface

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Figure 8. Upper panel: Distribution of the precipitating solar wind flux at the lunar surface. The typical values of thesolar wind velocity and density are taken as 450 kms1 and 7cm3, respectively. White rectangles show the field of viewof each channel (CH) mapped on the lunar surface. The center of the longitude and latitude is the subsolar point. Lowerpanel: Close-up view of the subsolar region showing the FOV of each channel mapped on the lunar surface.

this flow, a region void of solar wind is generatedbehind the Moon. The solar wind flowing behindthe obstacle is accelerated by a pressure gradi-ent created by its thermal velocity, enabling itspenetration into the void region. The solar windelectrons tend to penetrate into the void regionfaster than the protons, because of their muchlower mass, and the resulting charge separationwill cause an electric field that accelerates the pro-tons and decelerates the foregoing electrons, like inthe case of ambipolar diffusion. The temporal andspatial scale of the charge separation is related tothe electron plasma frequency (typically 10 kHz)and the Debye length (typically 20 m). Treating theplasma phenomena on a lunar global-scale, whichis typically 1000 km, such a microscopic view canbe simplified with the MHD approximation. TheMHD theory for plasma diffusion into the voidregion has been developed (see review by Samiret al 1983), and applied to the conditions at theMoon by Futaana et al (2005). The results ofFutaana et al (2005) suggest that for typical solar

wind conditions up to 4% of the upstream solarwind flux can reach areas as far as 10 beyond theterminator; while in slow solar wind velocity con-ditions 8% of solar wind can reach 20 beyondterminator.

3.3 Study of the magnetic anomaly regions

Although it was previously believed that the lunarmagnetic field was too weak to repel solar windions, intriguing magnetic anomalies on the lunarsurface have been found that can stand off the solarwind, thus creating the smallest known magne-tospheres, magnetosheath, and bow shock regionsin the solar system (Lin et al 1998). These mag-netic anomalies range in magnitude from a fewtenths of a nanotesla (nT; 1 nT = 105 G) to hun-dreds of nT, and ranging in size from a few km toseveral hundred km, and are present over much ofthe lunar surface (Hood et al 1979, 2001; Halekaset al 2001). The magnetized regions located nearthe Imbrium and Serenitatis antipodes are 1200and 700 km, respectively, with a field of 300nTfor the entire region. These anomalies are strongenough to form small dipole magnetic fields, creat-ing mini-magnetospheres, around 100 km in diam-eter locally due to interaction with the solar wind(Lin et al 1998). The solar wind flux cannot reach

the surface in these areas and no sputtering of sur-face material will occur. Thus the expected LENAflux will be extremely low from locations of mini-magnetospheres. Simulations of the variation of thesolar wind precipitation flux as seen from CENA


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Figure 9. Computed image of oxygen LENA flux as observed by CENA at the subsolar point (upper panel) and at theterminator (lower panel). Each channel (CH) has an intrinsic FOV of 9 25. The 7 channels correspond to a totallongitudinal coverage of about 20 on either side of the center point (see lower panel of figure 8).

(cf. figure 10) reveal that the magnetic anomaliesare clearly seen in the LENA images (Futaana et al2005), which will allow us to study these miniaturemagnetospheres and hopefully provide global mapsof such magnetic anomalies.

3.4 Mapping of the magnetic anomaly:Implications for space physics

A mini-magnetosphere is an expected but stillunproven concept. Its size is close to the pro-ton gyro-radius for the Moon conditions andthis effect gives rise to completely new physi-cal phenomena. Lin et al (1998) presented obser-vational evidence from Lunar Prospector thatthe interaction between lunar magnetic anom-alies and the solar wind could result in theformation of mini-magnetospheres on the Moon.Two-dimensional MHD simulations of the solarwind interaction with the lunar magnetic anom-alies made by Harnett and Winglee (2000, 2002)

have demonstrated that the crustal magnetic fieldscan hold off the solar wind and form a mini-magnetosphere. They concluded that the forma-tion is realized when the field strength is greaterthan 10 nT at 100 km above the lunar surface and

the solar wind ion density and velocity equal to10cm3 and 400 kms1, respectively. The MHDresults also indicated that mini-magnetospheresare much more dynamic than planetary sized mag-netospheres. Simulations of solar wind interac-tion with multiple dipoles on the lunar surfaceindicate that mini-magnetospheres will form withmagnetic field magnitude smaller than the lowerlimit for a single-dipole (Harnett and Winglee2003). Observations of non-thermal ions of lunar-origin by Particle Spectrum Analyzer/Ion Spec-trum Analyzer onboard Nozomi spacecraft alsosuggest the formation of mini-magnetospheres(Futaana et al 2003). The mini-magnetospheresshould also produce radio emissions (Kuncic andCairns 2004). The interplanetary magnetic field(IMF) will also affect the formation and shaping ofmini-magnetospheres. Flipping of the direction ofthe IMF from southward to northward can causethe mini-magnetospheres to double their size andchange from an elongated shock surface to a round

shock surface.It is thought that most structures resulting from

the Moonsolar wind interaction are too small tobe detected by in situ observations from an orbitat 100 km. LENA imaging technique is a possible


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Figure 10. Modeled solar wind flux (upper panel) and images of expected oxygen LENAs for magnetic anomaly locatedat the subsolar point. Magnetic anomalies are modeled by the disappearance of LENA flux due to the formation of mini-magnetosphere. The yellow line shows the spacecraft trajectory.

tool to detect the interaction and to measure thespatial size of mini-magnetospheres. The results ofsuch studies are very important for understandingplasma physics at an ion gyro-radius scale. More-over, the interaction between the magnetic anom-alies and plasma environment changes significantlywhen the Moon is in the solar wind (note that evenfor the steady solar wind the precipitation flux onthe day and night sides of the Moon are quite differ-ent), in the Earths magnetotail, or in the magneto-sheath. These natural variations of the incomingflux can be used to understand formation of themini-magnetospheres under varying conditions, aunique opportunity not present even for the Earthmagnetosphere.

3.5 Other scientific objectives of the SARA

In addition to the main objectives discussed above,the SARA instrument can also be used to study:

Space weathering on the Moon, Sources of the exospheric gases and comparative

studies of the exospheric gas production at theMoon and Mercury,

Interplanetary LENAs.

3.5.1 Studies of space weathering

Space weathering is a term used to refer tothe physical and chemical changes that occurto exposed material on the surface of an airless

body. Apart from micrometeoroid bombardmentand electromagnetic radiation, solar wind sputter-ing is an important contributor to the space weath-ering on the Moon, and all of them are responsiblefor the formation and maturation of the lunarregolith as a whole. Space weathering is of consider-able interest for studies of surfaces by remote sens-ing because it causes major changes in the opticalproperties. It is established in laboratory experi-ments that the proton irradiation of loose powdersresults in their darkening and reddening (see reviewby Hapke 2001). High albedo at regions of mag-netic anomalies is most probably a manifestation ofthis effect (Hood et al 2001; Richmond et al 2003,2005). Inside the magnetic anomalies, the regolithis shielded from the solar wind flux while the sur-

rounding areas receive a higher flux because of theformation of a mini-magnetosphere (Lin et al1998;Richmond et al 2005). Comparison of the LENAmaps with optical or infrared images can directlyreveal the quantitative relations between changesin the albedo and the total dose. It is needless toemphasize that an understanding of space weath-ering is of key importance to the lunar science.

3.5.2 Study of the Moons exosphere

The lunar exosphere is composed of atoms liber-ated from the lunar surface via interactions withsunlight, the solar wind, and meteorite bombard-ment. The relative importance of these processes isuncertain, though considerable progress has been


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made in the last decade (Stern 1999; Killen andIp 1999). One method of distinguishing exosphericsource mechanisms is by determining the energy(velocity) distribution of the atoms within theexosphere, since each process results in its ownunique velocity distribution of atoms ejected fromthe surface (see section 1.2). It is established that

sputtering contributes significantly to sources ofsuch atoms as Na, K, Al, Mg, Si, Ca (Potterand Morgan 1994; Killen and Ip 1999; Wurz andLammer 2003).

However, the major problem in quantitativestudies of the contribution from sputtering arisesfrom the lack of reliable sputter yields for differ-ent species of the mineralogical surface, especiallyunder the influence of space weathering. All theprevious studies rely on laboratory measurementsmade with specially prepared specimens and theo-

retical studies dealing with simplified assumptionsconcerning the structure of the sputtered materi-als. However, the yields strongly depend on themicrostructure of the material (solid, porous, looseaggregates, powders, etc.). It is only the directmeasurements in space with real planetary surfacesthat can establish these vitally important parame-ters. Absolute measurements of sputtered LENAswith mass resolution combined with knowledge ofthe solar wind flux and surface composition will beused to derive the sputter yields. These measure-ments are of significant importance not only for

studies of the lunar exosphere but also for that ofMercury and for asteroids studies.

3.5.3 Studies of the interplanetary neutrals

The LENA measurements on the Moon will alsocomplement the studies of neutrals in the inter-planetary medium, e.g., interstellar helium, theneutral component of the solar wind, and unknownneutral atom beams. The flux of the interstellarhelium results from the solar system motion rel-ative to the local interstellar medium (LISM). Ithas been detected directly by Witte et al (1993;see also Witte 2004). Recently, the LENA experi-ment on IMAGE made direct measurements ofthe neutral component in the solar wind (Collieret al 2001). These neutrals are produced due tocharge exchange between solar wind ions and theinterstellar hydrogen as well as due to the solarwind interaction with the interplanetary dust.However, the exact origin of this component isstill being debated. Recently, the IMAGE groupreported that there are some indirect indications,

coming from different satellites and techniques,that there might exist a third beam of neutralsapart from the interstellar and solar wind particles(Collier et al 2003). Barabash (private communi-cation, 2004) while analysing data from an ENA

instrument onboard Mars Express identified someunexplained features, which might be interpretedas the second neutral beam of unknown origin.More advanced measurements are needed for sort-ing out this issue. The SARA experiment with its160 FOV is capable of observing interplanetaryneutrals and thus will be in an advantageous posi-

tion to study these phenomena. Moreover, sincethe process of production of interplanetary neu-trals is similar to that of the ENA production inplanetary magnetospheres (e.g., Henderson et al1997; Bhardwaj and Gladstone 2000; Moore et al2000; Brandt et al 2001; Mauk et al 2003), thestudy of interplanetary ENA will add new dimen-sions to comparative ENA-planetology.

4. Relevance of SARA to theChandrayaan-1 mission

Indias first mission to the Moon, Chandrayaan-1,will carry a set of remote sensing payloads to pur-sue high resolution mapping of topographic fea-tures in 3-D and distribution of various mineralsand chemical species covering the entire lunar sur-face. SARA will complement these measurementsby providing coarse maps of elemental distributionover the entire Moon surface including some of thepermanently shadowed craters in the outermostlayer of regolith. Mass dependent LENA images

will also be used to constrain the surface miner-alogical composition as derived from the elementalcomposition maps. SARA will also provide directmaps of the magnetic anomalies capable of with-standing the solar wind dynamic pressure. Studieson lunar exosphere and space weathering effects onlunar surface will also be attempted.

Thus, the observations from SARA will providethe first information on LENA in the lunar envi-ronment and will supplement the scientific objec-tives of Chandrayaan-1. A replica of the SARA

CENA sensor is included in the payload of theBepiColombo Mercury Magnetospheric Orbiter.Therefore, conducting the SARA experiment onChandrayaan-1 opens ample possibilities for doingcomparative planetological studies in the near-future.

Acknowledgements

The Swiss contribution to SARA is made possibleby the financial support from the Swiss National

Science Foundation and by the Swiss PRODEXcommittee. A part of this research was performedwhile A Bhardwaj held the NRC Senior ResearchAssociateship at NASA Marshall Space FlightCenter.


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References

Adimurthy V and Ramanan R V 2004 Launch strategyfor Indian lunar mission; presented at InternationalConference on Exploration and Utilization of the Moon(ICEUM-6), Nov. 2226, 2004, Udaipur, India, abstractp. 55.

Barabash S, Lundin R, Andersson H, Gimholt J,

Holstrom M, Norberg O, Yamauchi M, Asamura K,Coates A J, Linder D R, Kataria D O, Curtis C C,Hsieh K C, Sandel B R, Fedorov A, Grigoriev A,Budnik E, Grande M, Carter M, Reading D H,Koskinen H, Kallio E, Riihela P, Sales T, Kozyra J,Krupp N, Livi S, Woch J, Luhmann J, McKenna-LawlorS, Orsini S, Cerrulli-Irelli R, Mura A, Milillo A, Roelof E,Williams D, Sauvaud J-A, Thocaven J-J, Winningham D,Frahm R, Scherer J, Sharber J, Wurz P and Bochsler P2004 ASPERA-3: Analyzer of space plasmas and ener-getic atoms for Mars Express, ESA Special publicationESA-SP-1240, 121139.

Behrisch R and Wittmaack K 1991 Introduction; In: Sput-tering by Particle Bombardment III; (eds) R Behrisch and

K Wittmaack (New York: Springer-Verlag) pp. 113.Betz G and Wehner G 1983 Sputtering of multicomponent

materials; In: Sputtering by Particle Bombardment II;(ed.) R Behrisch (New York: Springer-Verlag) pp. 1190.

Bhandari N 2004 Scientific Challenges of Chandrayaan-1:The Indian Lunar Polar Orbiter Mission; Curr. Sci. 8614891498.

Bhardwaj A and Gladstone G R 2000 Auroral emissions ofthe giant planets; Rev. Geophys. 38 295353.

Brandt P C, Barabash S, Roelof E C and Chase C J2001 Energetic neutral atom imaging at low altitudesfrom the Swedish microsatellite Astrid: Observationsat low (10 keV) energies; J. Geophys. Res. 106(A11)24,66324,674.

Bussey D B J, Lucey P G, Steutel D, Robinson M S,Spudis P D and Edwards K D 2003 Permanent shadow insimple craters near the lunar poles; Geophys. Res. Lett.30(6) 1278, doi:10.1029/2002GL016180.

Collier M R, Moore T E, Ogilvie K W, Chornay D,Keller J W, Boardsen S, Burch J, El Marji B, Fok M-C,Fuselier S A, Ghielmetti A G, Giles B L, Hamilton D C,Peko B L, Quinn J M, Roelof E C, Stephen T M,Wilson G R, Wurz P 2001 Observations of neutralatoms from the solar wind; J. Geophys. Res. 10624,89324,906.

Collier M R, Moore T E, Simpson D, Roberts A, Szabo A,Fuselier S, Wurz P, Lee M A, Tsurutani B T 2003 An

unexplained 1040

shift in the location of some diverseneutral atom data at 1 AU; Adv. Space Res. 34(1)166171.

Crider D H and Vondrak R R 2003 Space weathering effectson lunar cold trap deposits; J. Geophys. Res. 108(E7)5079, doi:10.1029/2002JE002030.

Eichorn G 1978 Heating and vaporization during hyper-velocity particle impact; Planet. Space Sci. 26 463467.

Elphic R C, Funsten III H O, Barraclough B L,McComas D J, Paffett M T, Vaniman D T and Heiken G1991 Lunar surface composition and solar wind-inducedsecondary ion mass spectrometry; Geophys. Res. Lett.18(11) 21652168.

Feldman W C, Maurice S, Lawrence D J, Little R C,

Lawson S L, Gasnault O, Wiens R C, Barraclough B L,Elphic R C, Prettyman T H, Steinberg J T andBinder A B 2001 Evidence for water ice near the lunarpoles; J. Geophys. Res. 106 23,23123,252.

Futaana Y, Machida S, Saito Y, Matsuoka A andHayakawa H 2003 Moon-related nonthermal ions

observed by Nozomi: Species, sources, and genera-tion mechanisms; J. Geophys. Res. 108(A1) 1025,doi:10.1029/2002JA009366.

Futaana Y, Barabash S, Holmstrom M and Bhardwaj A2005 Low energy neutral atoms imaging of the Moon;Planet Space Sci. (in press).

Goswami J N 2005 Chandrayaan-1: Technological and Sci-entific Challenges, presented at IAA Asia-Pacific regionalconference on Advances in Planetary Exploration, June2629, 2005, Bangalore, India.

Halekas J S, Mitchell D L, Lin R P, Frey S, Hood L, Acuna Mand Binder A B 2001 Mapping of lunar crustal magneticfields using Lunar Prospector electron reflectometer data;J. Geophys. Res. 106 27,84127,852.

Hapke G 2001 Space weathering from Mercury to the aster-oid belt; J. Geophys. Res. 106 10,03910,073.

Harnett E M and Winglee R M 2000 Two-dimensional MHDsimulation of the solar wind interaction with magneticfield anomalies on the surface of the moon; J. Geophys.Res. 105 24,99725,007.

Harnett E M and Winglee R M 2002 2.5-D particleand MHD simulations of mini-magnetospheres at the

Moon; J. Geophys. Res. 107(A12) 1421, doi:10.1029/2002JA009241.Harnett E M and Winglee R M 2003 2.5-D fluid simulations

of the solar wind interacting with multiple dipoles on thesurface of the Moon; J. Geophys. Res. 108(A2) 1088,doi:10.1029/2002JA009617.

Henderson M G, Reeves G D, Spence H E, Sheldon R B,Jorgensen A M, Blake J B and Fennell J F 1997 Firstenergetic neutral atom images from Polar; Geophys. Res.Lett. 24 11671170.

Hood L L, Coleman P J Jr and Wilhelms D E 1979 TheMoon: Sources of the crustal magnetic anomalies; Science204 5357.

Hood L L, Zakharian A, Halekas J, Mitchell D L, Lin R P,

Acuna M H and Binder A B 2001 Initial mappingand interpretation of lunar crustal magnetic fields usingLunar Prospector magnetometer data; J. Geophys. Res.106 27,82527,839.

Hovestadt D, Hilchenbach M, Burgi A, Klecker B,Laeverenz P, Scholer M, Grunwaldt H, Axford W I,Livi S, Marsch E, Wilken B, Winterhoff H P, Ipavich F M,Bedini P, Coplan M A, Galvin A B, Gloeckler G,Bochsler P, Balsiger H, Fischer J, Geiss J, Kallenbach R,Wurz P, Reiche K-U, Gliem F, Judge D J, Ogawa H S,Hsieh K C, Mobius E, Lee M A, Managadze G G,Verigin M I and Neugebauer M 1995 CELIAS Charge,Element and Isotope Analysis System for SOHO; SolarPhysics 162 441481.

Johnson R E 1990 Energetic Charged-Particle Interactionswith Atmospheres and Surfaces; (New York: Springer-Verlag).

Johnson R E, Leblanc F, Yakshinskiy B V and Madey T E2002 Energy distributions for desorption of sodium andpotassium from ice: The Na/K ratio at Europa; Icarus156 136142.

Kazama Y, Barabash S, Bhardwaj A, Asamura K,Futaana Y, Holmstrom M, Lundin R, Sridharan Rand Wurz P 2005 Energetic neutral atom imag-ing mass spectroscopy of the Moon and Mer-cury environments; Adv. Space Res., in press,doi:10.1016/j.asr.2005.05.047.

Killen R M and Ip W-H 1999 The surface-boundedatmospheres of Mercury and the Moon; Rev. Geophys. 37361406.

Kuncic Z and Cairns I H 2004 Radio emission from mini-magnetospheres on the Moon; Geophys. Res. Lett. 31,L11809, doi:10.1029/2004GL020008.


12/12


Lin R P, Mitchell D L, Curtis D W, Anderson K A,Carlson C W, Mc-Fadden J, Acun a M H , H o o d L Land Binder A 1998 Lunar surface magnetic fields andtheir interaction with the solar wind: Results from LunarProspector; Science 281 14801484.

Mauk B H, Mitchell D H, Krimigis S M, Roelof E Cand Paranicas C P 2003 Energetic neutral atomsfrom a trans-Europa gas torus at Jupiter; Nature 421920922.

Moore T E, Chornay D J, Collier M R, Herrero F A,Johnson J, Johnson M A, Keller J W, Laudadio J F,Lobell J F, Ogilvie K W, Rozmarynowski P, Fuselier S A,Ghielmetti A G, Hertzberg E, Hamilton D C,Lundgren R, Wilson P, Walpole P, Stephen T M,Peko B L, Van Zyl B, Wurz P, Quinn J M and Wilson G R2000 The low energy neutral atom imager for IMAGE;Space Sci. Rev. 91(12) 155195.

Potter A E and Morgan T H 1994 Variation of LunarSodium Emission Intensity with phase angle; Geophys.Res. Lett. 21 22632266.

Richmond N C, Hood L L, Halekas J S, Mitchell D L,Lin R P, Acuna M and Binder A B 2003 Correlation of a

strong lunar magnetic anomaly with a high-albedo regionof the Descartes mountains; Geophys. Res. Lett. 30(7)1395, doi:10.1029/2003GL016938.

Richmond N C, Hood L L, Mitchell D L, Lin R P,Acuna M and Binder A B 2005 Correlations betweenmagnetic anomalies and surface geology antipodal to

lunar impact basins; J. Geophys. Res. 110 E05011,doi:10.1029/2005JE002405.

Samir U, Write K H Jr and Stone N H 1983 The expansionof plasma into a vacuum: basic phenomena and processesand applications to space plasma physics; Rev. Geophys.and Space Phys. 21 16311646.

Sigmund P 1969 Theory of sputtering. I. Sputtering yield ofamorphous and polycrystalline targets; Phys. Rev. 184383416.

Stern S A 1999 The lunar atmosphere: History, status,current problems, and context; Rev. Geophys. 37(4)453491.

Thyagarajan K and Annadurai M 2004 Chandrayaan-1:Spacecraft design and technical challenges; paper pre-sented at International conference on Exploration andUtilization of the Moon (ICEUM-6), Nov. 2226, 2004,Udaipur, India, abstract p. 54.

Vasavada A R, Paige D A and Wood S E 1999 Near-surfacetemperatures on Mercury and the Moon and the stabilityof polar ice deposits; Icarus 141 179193.

Witte M, Rosenbauer H, Banaszkiewicz M and Fahr H 1993The ULYSSES neutral gas experiment: Determination of

the velocity and temperature of the interstellar neutralhelium; Adv. Space Res. 13(6) 121130.Witte M 2004 Kinetic parameters of interstellar neutral

helium; Astron. Astrophys. 426 835844.Wurz P and Lammer H 2003 Monte-Carlo simulations of

Mercurys exosphere; Icarus 164(1) 113.

Low Energy Neutral Atom Imaging on the Moon With SARA Aboard Chandrayaan-1 Mission

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