evaluationaccuracyofthegroundtestingisinsufficient, wecanimprovetheevaluationerroroftheground testingbychangingthemodulesizeorspringforce.Therefore,weconsiderthatthisindexcanbeusedin designingmodulesizeandspringforcemarginconsidering thedeployment testingaccuracy. Conclusions Wedefineanindexthatpredicts thedifficulty ofground deployment testingastheratioofgravitytorqueto deployment torque. Theindexcanbeusedtoassessthemaximum sizeofdeployment structures forwhich grounddeployment testingisfeasible. Asimpleplanartruss,whosedifficult indexvaluewaschanged from 1toapproximately 1000,wasusedtoestimate therelationship between theindexandtheevaluation accuracy ofground testing. Ourresultscanbesummarized asfollows. (1)Thedifference ofthedeployment driveforcebetween experimental andanalytical results is approximately 10%forthesimplestructure whoseDIV=Iandapproximately 3%ifthemassproperty isestimated indetail. (2)Weobtained anewempirical equation thatindicates alinearrelationship between DIV(upto approximately 1000)andevaluation errorofthegroundtesting. (3)Weconsider thatthemodular approach allowslargespaceantennas tobedesigned thatcanbewell assessed bygroundtesting. (4)Webelieve thatthisindexcanbeusedtodesignmodule sizeandspringforcemarginconsidering the deployment testingaccuracy. Acknowledgements Theauthors wouldliketothankDr.HidekiMizuno andDr.Mitsunobu Watanabe ofNTTNetwork Innovation Laboratories fortheirsupport andencouragement. Theyarealsograteful forthemanycomments madeby Dr.JinMitsugi ofNTTNetwork Innovation Laboratories. References [1]JinMitsugi andTetsuo Yasaka, Deployable Modular MeshAntenna -Concept andFeasibility, Proceedings of17thInternational Symposium onSpaceTechnology andScience, vol.1,1990,PP. 599-604. [2]Deployment ofthe15MeterDiameter HoopColumn Antenna, NASAContractor Report4938,Harris Corporation, 1986. [3]M.C.Natori, Tadashi Takano, ToshioInoue,andTakayuki Kitamura, Deployable MeshAntenna Structure forMUSES-B Spacecraft, 46thInternational Astronautical Congress, IAF-95-1.1.04, 1995. [4]MarkW.Thomson, TheAstromesh Deployable Reflector, 6thInternational MobilE;Satellite Conference, pp.230-233, 1999. [5]Hiroshi Sakamoto, KenjiUeno,andKohjiHorikawa, On-Orbit TestofMultibeam Communication Equipment onKiku-6inElliptical Orbit47thInternational Astronautical Congress, IAF-96-M.2.0.2, 1996. [6]AkiraMeguro, AkioTsujihata, Naokazu Hamamoto, andMasanori Honma, Technology statusofthe13 maperture deployment antenna reflectors forEngineering TestSatellite VIII,ActaAstronautica Vol.47,Nos. 2-9,pp.147-152, 2000. [7]Hironori Ishikawa andAkiraMeguro, Highaccuracy evaluation method ofdeployment characteristics for largedeployable structures, 9thEuropean Space Mechanisms andTribology Symposium, 2001.pp. 137-144. [8]Mitsunobu Watanabe, Kazuhide Ando,Akihiro Miyasaka, andSatoshi Harada, Mechanical Error Evaluation onOnboard Modular MeshAntenna, 50thInternational Astronautical Congress, IAF-99-1.1.01, 1999. [9]Kazuhide Ando,Akihiro Miyasaka, Hironori Ishikawa andMitsunobu Watanabe, TheModular Mesh Reflector developed atNTT,International MobileSatellite Conference 99,1999. [10]AkiraMeguro, Satoshi Harada, andMitsunobu Watanabe, KeyTechnologies forHighAccuracy Large MeshAntenna Reflectors, 51stInternational Astronautical Congress, IAF-00-1.1.0.5, 2000. NASA/C P--2002-211506 357