value.ThesameprocesshastobedoneforotherDlVs.Therelationship betweenDIV(1-845)andthe evaluationerrorofthegroundtestingisshowninFigure11.Evaluationerrorofthegroundtestingisgivenin unitsofpercentage. TheevaluationerrorofthegroundtestingincreasesasDIVincreasesasshownin Figure11. Figure12showsthedeployment driveforceforDIV=160.Here"DDF"denotesthedeployment driveforce, "BestFit"denotestheprofilethatminimizesthedifferencebetweentheexperimental andanalysisresults. Theminimizeddifferencevaluebecomeslargerwhenthefluctuationincreases.Therefore,weconsidered thatthefluctuationvalueoftheevaluationerrorofthegroundtestingistheratiooftherootmeansquareof thedifferencebetweenDDFexperiment andDDFBestFittothetruevalue.Therelationship betweenDIV andtheevaluationerrorofthegroundtestingincludingthefluctuationisshowninFigure13.Evaluation errorofthegroundtestingisgiveninunitsofpercentage andorepresentstheevaluationerrorofFigure11. TheevaluationerrorofthegroundtestingisminimumwhenDIV=1whereastheevaluationerrorofthe groundtestingincludingfluctuationismaximum. Empirical equation Byassuming alinearrelationship between DIVandthemaximum valueoftheevaluation erroroftheground testing, weobtained thefollowing empirical equation (1). R=0.1i+13.8 (1) Here,irepresents DIVandRindicates theevaluation erroroftheground testing. Intheempirical equation, theevaluation erroroftheground testingisapproximately 100%whenDIV=800. Therefore, wecanconclude thatitisinfeasible touseground testingtoevaluate deployable structures whosedifficulty indexvalueexceeds 800. Theevaluation errorofthegroundtestingwasassessed usingaplanartrussandthesuspension system. Thismodelisverysimple anditwaseasytoevaluate bytheanalysis tool.Weconsidered thatthe evaluation erroroftheground testing inthismodelwasthesmallest among allrealistic deployable structures. Accordingly, thisindexcanbeusedforanydeployable spacestructure. Wewillmakeamodel thatconsists ofthreeconnected planartrusses andcalculate theevaluation errorofthegroundtesting. We willverifytheempirical equation anddescribe theresultsinafollowing paper. Modular MeshAntenna Oneofthemethods usedtoestimate thedeployment characteristics oflargespacestructures byground testingistodesignalargespacestructure usingmodular components. Thedesired sizecanbecreated by combining several basicmodules, andthecharacteristics oftheentirestructure canbepredicted fromthe characteristics ofthebasicmodule andtheeffectofcombining them[13].Anexcellent example ofamodule structure isthelargemodular satellite antenna, calledthemodular meshantenna, thatNTThasbeen developing. The18mX17mmodular meshantenna consists of14basicmodules. Eachbasicmodule, whichis4.8m indiameter and0.6mthick,consists ofameshreflector andadeployable trussstructure asasupport structure, asshowninFigure14[14][15]. Module construction isshowninFigure15.Thedeployable truss structure iscomposed ofsixribstructures thatarelocated around acenterbeam.Thedeployable truss structure hasslideandcoilsprings, whichprovide thedeployment force.Eachribstructure consists ofthe upperbeam,thediagonal beam,thelowerbeam,thesidebeamandtwosynchronous beams. Therib structure deploys orstowsbymoving themsimultaneously. Weapplied theempirical equation tothemodular meshantenna. Thecharacteristics oftheentirestructure canbepredicted fromthecharacteristics ofthebasicmodule andtheeffectofcombining them.Therefore, itisnecessary totestthemaximum number ofmodules combined atonepart.Therelations amongthe number ofmodules, theDIVofthemodular meshantenna, andtheevaluation erroroftheground testing areplottedinFigure16.Itisnecessary totestthreemodules because threemodules canbecombined at thesamepointasshown inFigure14.Inthiscase,itisthought thattheaccuracy ofthedeployment characteristics issufficient because theevaluation erroroftheground testingisapproximately 20%.Ifthe NASA/CP--2002-211506 356