ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
MODIS LTUScanner DragTorque Measurement, MeanDrag=0.086N-m 0.12 0.11 0.1 EI z _"0.09 E O 0.08 O3 a 0.07 0.06 0.05 0 5 10 15 20 25 30 35 40 45 Time(seconds) Figure18.MODIS LTUScanner Steady StateDragTorque MODISLTUScanner PhaseError 6 G" 25 -'-4UJ p_3¢- 13_ 2 1 0 -1.................... i........................................................................................................................................................... | ................... I.............................................................................................................................. :............................ 0 2 4 6 8 10 12 Time(seconds) Figure19.MODIS LTUScanner PhaseError 13
Conclusions Thesteadystatedragtorques measured ontheMODIS EMandLTUscanner unitswereabout67mN-m (9.4oz-in)and87mN-m(12.2oz-in)respectively indicating abeginning-of-life andaend-of-life torque margin ofgreater than20.Themoreimportant parameter ofphaselockmargin forbothunitswasa healthy 200percent. Because ofthedesignsimilarities between theEMandLTUscanner unitsandthe PFMandFM-1MODIS scanners, itwasconcluded thatthePFMandFM-1unitMODIS scanners had sufficient margin forafive-year mission lifeontheEOS-AM (Terra) andEOS-PM (Aqua) programs respectively. Lessons Learned Asawornslipringwasthecauseofheaterlossintheaccelerated teststation, itwasshownthatthetest equipment mustbemorerobustthanthehardware beingtested. Also,inthepresence ofgravity, considerations fortheorientation oftestsamples shouldbegiven.Wherefeasible, rotation ofthesamples shouldbeperformed tocounter theeffectsofgravity. Thelabyrinth sealshouldmatchthatoftheflight configuration. Andlastly,whentestingmechanical systems consider thefrequency ofthetestapparatus. Inthistestitwasnotedthatjitter,seenduringlifetesting, waslikelyduetothecantilevered testarm resonating orcoupling withtherotational speedofthebearings. Acknowledgements J.Uber,S.Cicchelli, andM.Roberto, NASAGoddard SpaceFlightCenter. A.DeForrest, Raytheon Systems Company, SantaBarbara Remote Sensing. L.Alegre, S.Natvipada, D.Owens, T.Phan,P.Tokeshi andH.Tsui,MoogSMD. N.St.PierreandM.LaRochelle, NyeLubricants References 1.BrianJ.Dietz,StevenG.VanDyk andRoamer E.Predmore, "EarthScanner Bearing Accelerated Life Test",34mAerospace Mechanisms Symposium, May2000,pp303-316. 14
,.-/.j/f' DryLubrication ofSpace-Rated Tribocomponents withDiamond-Like Carbon Coatings G.Pont',CDonnet*', J.Fontaine*', MBelin'*,T.LeMogne'*, YBerthier-', SDescartes*'*, CHeau.... Abstract Thispaperdetailsafouryeareffortinthedevelopment ofDiamond-Like Carbon (DLC)coatings forspace related tribocomponents. Afterabriefpresentation ofthecoating deposition technique, flat-on-disc tribometer results areshown. Theseresults, coupled withanalytical characterizations, showthatthe coatings tribological behavior strongly depends ondeposition parameters. Thedeposited filmsmaybe divided intotwocategories: thehigh-friction onesandtheultralow-friction ones.Tribological testshave beenperformed onbearings inhighvacuum conditions afteroptimizing theadhesion underlayers. The results showthattheDLCtestedcouldbeverysatisfactory forsomeapplications. SomeothersDLC coatedcomponents (gears, screw-nut) willbetestedinaverynearfuture. Introduction DLCcoatings asdrylubricants arebeingstudied allovertheworldbecause theyareverypromising when usedundercertain conditions. Forexample, friction coefficient underUltra-High-Vacuum (UHV)canbe verylow.Today, someindustries already useDLCasadrylubricant (harddisksdrivesincomputer manufacturing forexample). Afewyearsago,CNES(French SpaceAgency) andLTDS,studied various commercial DLCcoatings in ordertoassess thefilmcomposition parameters thatledtoeffective coatings forspacemechanisms dry lubrication. Duringthisphase,strongcontacts wereestablished withtheIBMResearch Division (Watson, NY),whoprovided DLCsamples showing ultralow frictionunderUHV[1]oThen,CNES, LTDS,LMCand HEF(asurface treatments specialized Frenchcompany) decided togofurtherinthedevelopment ofDLC coatings thatcouldbeusedinthespaceindustry [2].Thegoalofthispaperistopresent themainresults ofthisstudyassomeDLCcoatedspacemechanisms components (bearings, gears,screw-nut) arebeing tested. WhatisDLC? ADLCisanamorphous metastable material deposited byPVDorPECVD techniques onafew micrometers. Itconsists ofadisordered covalent network ofcarbon atoms, containing several carbon hybridization (mainly sp2andsp3),inwhichdifferent elements, mainlyhydrogen, sometimes impurities or dopingelements (nitrogen, fluorine...) canbeincorporated. Themainparameters describing thestructure arethusthesp2/sp3ratioandthehydrogen content [3],whichinturnstrongly depend onthedeposition process. ManykindsofDLC,withvarious properties, havebeendeveloped allovertheworld.Infact,the'DLC' terminology describes moreafamilyofmaterials thanasinglematerial. Depending ontheelaboration process, DLCwithawiderangeofhydrogen content (a-Cora-C:H) maybedeposited, showing high(up to0.7)orverylow(downto0.007)frictioncoefficient [4].TheDLCwehavebeeninterested induringthis studyarehydrogenated DLC(a-C:H), produced without dopingagents. *CNESMechanisms Department, Toulouse, France _Laboratoire deTribologie etdeDynamique desSystemes (LTDS), Ecully,France Laboratoire deMecanique desContacts (LMC),Villeurbanne, France ....HEF,Andr_zieux-Boutheon, France Proceedings ofthe3_hAerospace Mechanisms Symposium, AmesResearch Center,May9-11,2001 15
Experimental setup Deposition Process Thedeposition method, selected atthebeginning oftheproject, isahybridtechnique ofMagnetron Sputtering andPlasma Assisted Chemical VaporDeposition (PACVD). M.^,. Cathode _Gasprecursorovlngma_r_ /  Ii,J,/ Infrared heater,, "__ _E]  _._ Pumping \Samples holders (planetary movement)unit Figure1.HEFIndustrial Reactor [2] Samples areplacedonholders havingaplanetary movement inthereactor sothatDLCthickness should beconstant allaround cylindrical-shaped samples, whichisthecaseformostofthetribology components usedinspace. Allthecoatings consist inagradient, fromtitanium asunderlayer, toDLC,inorderto reachastrongadhesion onthesubstrate. Thisgradient isobtained byincreasing CFFiratiosfromthe substrate totheDLCitself,byadjusting thedeposition conditions duringthedeposition (nature andflowof gaseous precursors, biasvoltage). Optimization ofthefunctionally .qradient filmsforUHVlowfrictionandwear Inordertooptimize thecoatings, friction testshavebeenperformed withAISI440Csamples while analytical characterizations havebeenperformed withsiliconones.Friction testshaveconsisted ina reciprocating pin-on-flat configuration, asliding speedof1mm/sandamaximum Hertzian contact pressure of1GPa.Alimitednumber of500cycleshasbeenperformed todiscriminate thesetoffilms, depending ontheirdeposition conditions. Thecoatings havebeensystematically deposited ontheplane counterface, whatever thebiasconditions. Thefilmshavealsobeendeposited onthesteelpin counterface atdifferent deposition parameters tocheckifthetribological behavior depends ornotonthe deposition ofthefilmsonbothcounterfaces, incomparison tothedeposition ontheplaneonly.Eachtest hasbeenperformed several timesinthesameconditions tocheckthemeasurements reproducibility. All thetestswereperformed atroomtemperature eitherinambient airatrelative humidity RH=40-60%, orinultrahigh vacuum (UHV)at10.8Pa. Thefilmshavebeencharacterized byRutherford Backscattering Spectroscopy (RBS)andForward Recoil ElasticScattering (FRES) todetermine thecomposition, andbyFourier-Transform InfraRed spectroscopy todetermine thenatureoftheCHbonds.Thefilmthicknesses havebeenmeasured bycrosssectional micrographs. Thefilmdensity valueshavebeenestimated bycombining theprevious thickness values withthethickness deduced fromRBSmeasurements (ing-cm-2). Theresidual stress hasbeen determined fromthecurvature induced inthesiliconwaferbythedeposited film[5]. 16
Experimental results Linkshavebeenestablished between thecoatings tribological behavior andtheircompositions. For example, thelinkbetween thefriction coefficient andthehydrogen content (measured withFRES)has beenhighlighted (Figure 2).Therereallyisathreshold between thehighfrictionDLC(upto0.7friction coefficient forupto47at.%hydrogen content) andthelowfrictionDLC(downtolessthan0.01friction coefficient forhydrogen content greater than47at.%).Thishydrogen content mayberegulated bymany parameters ofthedeposition reactor, asforexample thebiasvoltage. 1................................................................... ...................................................................  ZZZI_ZZZIZZZZZZZZZZZIZ[ZZI 0.1!.:_:-_--.:_:_:_--_! !!!!_-_!!!.:-!!!}[!-:}!--_:!:?--!!!!!!!_:-!!}-!:-.:.:!!!!! g .:_:.-.::_:_:_-_-_:.:_:_:_-_:.:.::_!:_-:-_:_:_-:.:.:_:.-_-:.-.:_:_:_-_:.-_:_:_:_:.:_-_-.:.-.:_:_::_-_-.-.:.:::.:_:_-_-:..................................................................  .................................... %................ ......... io.ol!!!!!!!!!!!!!!!::!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!_*_!!!!!!!!!! ...................................................................  :[[[_-ZZ[_-ZZIIZ[][Z-Z Z[[[I[]I][[:Z:Z[[[Z Z[[I][[Z:Z[[Z ................................................................... 0.001 , , , 35% 40% 45% 50% 55% Totalhydrogen content (at.%) Figure2.Steady-state friction inUHVversus hydrogen content ofthefilms[6] OnFigure3,onecanobserve thedifference between lowandhighfrictionDLCcoatings. The-60Vbias voltage DLCexhibits averylowfriction coefficient andaverysmallwearwhilethe-120Vbiasvoltage DLCexhibits arelatively highfriction coefficient andahigherwear.The-60Vbiasvoltage DLC corresponds to51at.%hydrogen content andthe-120Vbiasvoltage DLCcorresponds to45at.% hydrogen content. So,thetribological behavior oftheDLCstrongly depends onthedeposition conditions. _.. 0 :G 's o0.7 0.6 0.5 0.4 0.3 0.2 0.1 0i 0 100 400 500-60V ,/! 200 300 Slidingcycles,N Figure3.Friction coefficient evolution inUHV,versus number ofreciprocating sliding cycles, for thefilmsdeposited at-60Vand-120V.Optical micrographs oftheweartracksofthepins(left) andontheplanes (right)after500cyclesareshown inset[6]. 17
Optimized DLCcharacteristics Aftertheoptimization process, coatings wereselected inordertobetestedwhilecoated onreal mechanisms parts.Themaincharacteristics ofthesecoatings aresummarized Table1. Table1.Optimized DLCcharacteristics [5] Friction coefficient underUHV 0.01 Friction coefficient underambient air 0.2 4 Typicalthickness (including underlayer) (pro) Toplayerhydrogen content (at%) Density (g.cm-_) Residual stress(GPa)51 1.5 -0.6 Environment sensitivity Sometestshavebeenperformed inordertocheckenvironment DLCsensitivity, withIBMDLCcoated samples [1][7].Thehydrogen content ofthecoating was42at.%andthetestsconditions werethesame thanthosedescribed before. WhiletheseIBMfilmsshouldnotbedirectly compared totheTiCHfilms presented inthispaper,theyhavebeenconsidered asmodelDLCfilmsforthestudyoftheenvironmental effects onthefriction. Bothbelongtothehydrogenated DLCfilmcategory, deposited bythesamebasic technique (PACVD). SincetheIBMreactor ishowever different thantheHEFone,thefilmsdonotexhibit exactly thesameproperties forthesamecomposition. Thisresultisparamount forthestudyofDLCfilms, whoseproperties andtribological behavior arealways relatedtotheiroptimization onagivendeposition reactor only. Itwasfoundthatthevalueofthefrictioncoefficient doesn't depend ontheoxygen partialpressure. Thisis notthesameregarding watervaporpressure. Figure4presents thefrictioncoefficient variations andthe watervaporpartialpressure asfunctions ofthenumber ofcycles. 0,5 0,4 r..) _0,3 0 ._0,2 U Ii 0,130 0,5 0,4 ¢.- ___0,3 .£0,2 0,1 0252 20_(3. L --*15_ 10_ 55 _ 0 lO00 15o0 Cycles1E+02 J1E+01 1E+00Ei1E-01_._ :1E-02B 1E-03_ e_ 1E-04t1E-05g 1E-06_ 1E-07 0 1E-08 0 500 0200 400 600 800 Cycles Figure4.DLCwaterpressure sensitivity [7] Thefrictioncoefficient reallyseemstobewatervaporsensitive :itrangesfromsomehundredths under UHVtosometenthswhenthepressure ishigh.Thereisastepinthefrictionincrease whenthewater vaporpartialpressure reaches 0.5hPa(Rh=2%). Theeffectofthiswatervaporseemstobereversible : whenthepressure isreduced untilUHV,thefrictioncoefficient returns toitsinitialvalueunderUHV.The proposed explanation ofthisphenomenon isthatthewatervaporcouldinhibitthetransfer mechanisms andthusincrease friction [7].Thishastobeconfirmed withsomeadditional tests,andespecially with HEFDLCs.But,inthecaseofspacemechanisms lubrication, whentestshavetobeperformed underair beforerunning underUHVinspace,thisreallyisaninteresting result,whenonecompares thisbehavior withtheirreversible dramatic tribo-oxidation ofMoS2filmswhenexposed towatervapor. 18
DLCcoated mechanisms components testing BallBearinqs Thefirsttestsoftheoptimized DLCcoatings wereperformed onangular contact ballbearings fromADR Company. TheDLCtestedhasbeendeposited atabiasof-60Vandacurrent intensity of2A.Their characteristics aresummarized Table2. Table2.Tested bearings characteristics Outside diameter (mm) Insidediameter (ram) Balldiameter (mm) Number ofballs Contact angle(o) Preload (N) Induced Contact Stress(MPa) Material Partscoated55 35 3.969 26 15 100±10 1130 AISI440C Rings(tracks) andcages Afterthefirstbearing pairwascoated, theexternal ringsappeared tobeverydeformed. Thiswasdueto thejointeffectofthetemperature andtheringssupport. Weproceeded toatestthatmeasured the highest temperature duringtheprocess. Itappeared tobehigherlocallythanthestainless steeltempering temperature. Thismaximum temperature wasreached duringtheetching ofthesubstrate, priorto deposition. So,wedecided toadjusttheetching temperature and,also,tochange theringsupport geometry inordernottoradiallystresstherings. Asecond pairofbearings wascoated andtested. First,thetorquewasmeasured underairinorderto verifythatnomajorchanges hadoccurred withthecoating. Then,thebearing pairwasplacedinaUltraHigh-Vacuum chamber anda'lifetest'began.Thistestconsisted inacontinuous rotation movement (30 rpm),duringwhichthetorque, thetemperature insidethetorquemeter andnearoneofthemotionless ringsweremeasured. Figure5isapicture ofthetestbenchandTable3showstheevolution ofthe torqueduringthetest. Figure5.TestBench 19
Table3.Torque Measurements During Bearings Tests Beforedeposition* Justafterdeposition Nitrogen test Lifeteststart Stabilized torque Endoftest *Thistestisdonewithafewli(IAtmosphere Air Air Nitrogen UHV UHV UHVMeanTorque (cN-cm) 50 55 8O 75 12 15 uidlubricant inordertoavoidbearings damagesTorque Noise(cN-cm) 110 100 3O 60 15 >200 Afterarunning-in period(10000 revs),thetorqueappeared tobestableandnoiseless formorethan 400000 revs.Then,thetorquenoisebegantoincrease anditwasdecided tostopthetestat500000 cyclesandtoinspect thebearings inordertotrytofindoutwhatcaused thenoiseincrease. Bearing inspection showsthatthirdbodyflowstakeplaceinthebearing. Onecanobserve thephenomenon on Figure6. Theracesshowdifferent kindsofwearwithathirdbodyflowgoingoutside theracewhiletheballsshow thatsomeDLChasbeentransferred fromtheracetotheballs.Thewearofthecagesisverysignificant andcouldhaveledtothetorquenoiseincrease attheendofthetest.Also,thiswearshouldbereduced withabetterqualitysurface insidethecagepockets. Somemachining markscanbeeasilyobserved and weknowthatDLCdon'tlikeroughsurfaces• So,anewtestisgoingtobeperformed withimproved cages. InnerRing Ball CuttedcacCage Figure 6.SomePictures fromTested Bearings 20
RFSwitchBearin,q RADIALL Company usesasmallbearing fromRMBcompany inT-typecoaxial switches. Thisbearing is submitted toquickoscillating movements (60°amplitude inabout20msineachdirection). Anaxialload ofabout15Nisapplied tothisbearing viatheactuator magnet. Themaincharacteristics ofthebearing aresummarized Table4. Table4.RFswitch bearing characteristics Outside diameter (mm) Insidediameter (mm) Ballsdiameter (mm) Number ofballs Axialloadatrest(N) Switching axialload(N) Material Partscoated11 15 23 AISI440C Rings(tracks) andcages Twokindsoftests,relative tothebearing lubrication, havebeenperformed atRADIALL. First,theexisting MoS2lubrication underambient atmosphere (50%RH)ledtoswitching problems atabout50000 commutations. Theneedis300000 commutations underspacevacuum condition, buttheproduct canbe operated bycustomers before launch undervariable andindefinite conditions (humidity, pressure, number ofcommutations...) duetostorage, ground operations, transportation. SoideallyRADIALL wishes theproduct tobeabletowidthstand thecomplete life(300000 commutations) including aperiodinground condition aswellastheperiodinorbitcondition. Therecommendation fortheuseoftheMoS2lubrication mightbedifficult toachieve forgroundoperations, storage andtransportation. Thereisaneedforanew drylubricant. RADIALL decided tolubricate thebearing withthesameDLCthatwasdeposited ontheADRbearings presented above. Withthepresent DLC,therewasnoproblem toperform thewholenumber of commutations underatmosphere. Atthebeginning of2001,RADIALL isgoingtoperform aqualification testssequence (including commutations underUHV)withaDLClubricated bearings switch.Thisreallyis thefirstcommercial application ofourDLC. Sincethequalification testdealswiththewholecommutator, itisnotpossible tohavedirectinformation onthebearing behavior. Incorporating bearing dedicated sensors wouldsignificantly modify the commutator. Ithasthusbeendecided toperform bearing testsinordertocompare DLCtoMoS2using torquemeasurements onaspecific testbench. Gears Asetoffourgears(twoAISI440Cgearsandtwo35NCD16 gears)hasbeencoatedwiththesameDLC usedhereand willbetestedonaspecific testbenchin2001Figure7isapictureofagear,showing the goodvisualqualityofthecoatin Figure7.DLCcoated gear(teethheight2mm) 21
Screw-nut FortheMarsNetlander mission, the'lnstitut dePhysique duGlobedeParis'(IPGP), SODERN company andCNESaredevelopping aVeryBroadBandseismometer inordertobetterunderstand theMartian internal structure [8].Thisseismometer consists inapendulum (spring andmass)rotating around an elasticpivot.Thispendulum beingverysensitive, ithastobebalanced viaamassdisplacement system, drivenbyamotorandascrew-nut device. Thescrew-nut devicehastobedesigned takingintoaccount thefactthattheseismometer isplacedina vacuum chamber inordertoobtainagoodqualitypendulum. Thescrewismadeoftitanium, itsdiameter is3mmanditsstepis0.25mm.Backlash isremoved fromthesystem byusingapairofhalf-nuts separated byaspringwhichinduces a0.2Nradialpreload. Half-nuts areusually madeofbrass.Tests withthislastconfiguration showed limitedlife,soithasbeendecided totestDLC-coated nutsmadeof titanium. Testshavebeenperformed withandwithout DLClubrication onthehalf-nuts inordertoassess DLC effectiveness. Motorcurrent wasmeasured ineachdirection, underairorvacuum (<103Torr).Allthe resultsshownbelowrepresent thecurrent instabilized phase,aftertherunning-in period. Figure8shows thevalues(averages overthewholetestsequence) ofthemotorcurrentforeachdirection, withorwithout DLClubrication, underair(6hourstest)orvacuum (1hourtest)atambient temperature. Thenumber of cyclesinduced bythetestsduration isquiterepresentative ofthemission needs. 30 [Air 25 20 15 10 g5 r_-0 o-5 -10 -15 -2O -25It--Max --Min ItI Way1Way1Way2Way2Way1Way1Way2Way2 NoDLC DLC NoDLC DLCNoDLC DLCNoDLCDLC Figure8.Comparison between non-lubricated andDLC-lubricated nut Table5showstheinfluence (percentage) ofDLConthemotormeancurrent andonthecurrent noise, defined asthedifference between themaximum current andtheminimum current. Except forthecurrent noiseundervacuum inthefirstdirection (way1),DLCreduces significantly thevalues ofthemean current andthecurrent noise.Inspection ofthescrew-nut didn'tshowanyproblem ofwear,andlong-life testswillbeperformed. Asitwasshownwithflat-on-disc tests,DLCseemstobeagoodlubricant when pureslidingoccurs, whichisthecaseinaplainscrew-nut system. Table5.DLCinfluence onmotorcurrent (%) MeanCurrent Air -1 VacuumWay1 Way2 Way1 Way2-2O -5 -7Current Noise -43 i-59 +9 -45 22
Conclusion Diamond-Like Carbon (DLC)coatings, deposited byahybridtechnique ofmagnetron sputtering and plasma-assisted chemical vapordeposition, havebeenstudied. Friction tests,coupled withanalytical characterizations, showthatthecoatings exhibit awiderangeoffriction behavior, depending onthe coating composition and,thus,onthedeposition conditions. Anunderlayer optimization studyhasalso beenperformed inordertoobtainastrongadhesion onthesubstrate. Theselected solution isagradient fromtitanium toDLC,fromthesteelsubstrate tothesurface. Promising tribological results havebeenobtained withDLCdeposited ballbearings eventhough alotof additional workstillremains. Forexample, thecage/ball contacts willbeoptimized inordertodecrease thesignificant wearobserved. Nevertheless, asmallDLCcoated RFswitchbearing showed better behavior thanMoS2coated bearing andcouldledtothefirstspacecommercial application oftheDLC coatings ifthequalification testssucceed. Someothercomponents aregoingtobetestedinthenext months (screw-nut device, gears,otherbearings...) Theworkpresented hereisveryinnovative because itcouldleadtothequalification ofanewspacemechanisms lubrication solution. Itisconsistent withthe current development ofdiamond-like carbon filmsforvarious applications, including lowfrictionandwear inextreme conditions. Acknowtedgments Wearegrateful totheRegion Rh6ne-AIpes forsupporting thepresent study. WethankN.Striebig, S.Cacho, O.PotandB.BrientfromIPGPforthescrew-nut tests,whichhavebeen performed inIPGPlaboratories. References [1] Donnet Ch,LeMogne Th,BelinM,SicreJ,PontG,GrillA,PatelV,Jahnes C;"Diamond-Like Carbon Coatings forVacuum andSpaceTribology"; 7thEuropean SpaceMechanisms andTribology Symposium; Noordwijk (Ned);October 1997 [2] Fontaine J.;"Elaboration, Caracterisation etTribologie deCouches Minces DLC(Diamond-Like Carbon) pourlaLubrification desMecanismes Spatiaux"; ThesedeDoctorat; 2000. [3] Donnet Ch,Fontaine J.,LeMogne Th,BelinM,TerratJ.P.,HeauCh.,PontG;"Tribologie de Couches Minces deCarbone pourMecanismes Spatiaux"; Journee Technique CETIM; December 1998. [4] GrillA.,Diamond andRelated Materials, 8(1999)428. [5] Fontaine J.,Donnet Ch,LeMogne Th,BelinM,Berthier Y,TerratJ.P.,HeauCh.,PontG; "Towards theSolidLubrication ofSpaceMechanisms byDiamond-Like Carbon Coatings"; 8thEuropean SpaceMechanisms andTribology Symposium; Toulouse (France); Sept1999. [6] Donnet Ch,Fontaine J.,LeMogne Th,BelinM,TerratJ.P.,HeauCh.,VauxF.,PontG; "Diamondlike Carbon-Based Functionally Gradient Coatings forSpaceTribology"; ICMCTF'99; 1999. [7] Donnet Ch.,LeMogne Th,Ponsonnet L.,BelinM,GrillA.,PatelV.,Jahnes C.;"TheRespective RoleofOxygen andWaterVaporontheTribology ofHydrogenated Diamond-Like carbon Coatings"; Tribology Letters4;1998. [8] Cacho S.,Lognonne P.,Karczewski J.F.,PontG.,CosteG.;"AVeryBroadBand3Axis Seismometer toStudyInternal Structure ofMars"; 8thEuropean SpaceMechanisms andTribology Symposium; Toulouse (Fra);September 1999. 23