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A quantitative assessment is provided of the difficulty of ground deployment tests and evaluates the validity of modularized deployment testing for large space structures. An index that well shows the difficulty of ground deployment tests is the ratio of gravity force to deployment force. The relationship between this index and the accuracy of deployment tests is calculated using an analysis model of the large deployable antenna reflectors onboard Engineering Test Satellite VIII (ETS-VIII). The index showed that a deployment structure whose diameter is more than 10 m has insufficient evaluation accuracy; thus the structure should be divided into modules. The index also showed that the single module of the large deployable antenna onboard ETS-VIII is of the appropriate size to evaluate deployment reliability. The influence of module connection on the deployment motion is also examined. The cross correlation between the changes in strain energy profile during deployment in a single module and those in combined modules is calculated to show how many modules should be connected and tested. The resistance force that arose due to the module connection is also calculated using the beam strain energy. It is clarified that ground deployment testing for four combined modules should be conducted in addition to the ground deployment testing for a single module when the deployment force margin is not large enough. Nomenclature A= cross-section area C M = cross correlation between changes in strain energy profile during deployment in a single module and in combined modules D a = deployment force adjusted to agree with experimental results D f = true deployment force obtained by microgravity testing E = Young's modulus e E = estimation error of the deployment drive force f eq = equivalent resistance force I = second moment of area i D = gravity force/deployment force L = beam length M = number of combined modules N = number of data in strain energy profile during deployment used to calculate C M P beam = total bending strain energy p b = bending strain energy per unit volumē p i = average potential energy in beams during deployment for ith module in isolation ‡ Senior Engineer, Engineering Test Satellite VIII Project, 2-1-1 Sengen, Tsukuba-city.p M i = average potential energy in beams during deployment for ith module among M combined modules q = generalized parameter for the system equation of deployment motion s = hinge displacement u = translational displacement at edges of a beam w = mode shape function of a beam θ = deployment angle σ i = standard deviation of potential energy in beams during deployment for ith module in isolation σ M i = standard deviation of potential energy in beams during deployment for ith module among M combined modules φ = rotational displacement at edges of a beam

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Engineering Test Satellite-VIII (ETS-VIII) is a three-axis-stabilized geostationary satellite intended to develop the advanced technologies for a large-scale spacecraft bus. Some of the objectives are development, test, and verification of Large Deployable Reflector (LDR). A largescale reflector is one of key technologies for geostationary satellite communication using handheld size terminals. The reflector functions and performances will be confirmed by S-band frequency mobile communication experiments using the reflectors and active phased array feeds. The most distinctive feature of the reflector is an adoption of the module structure. The reflector is an assembly of 14 independent hexagonal modules. For this concept, technologies to estimate multimodule performance from single-module performance are important. The estimating technologies are deployment analysis, structural analysis, thermal analysis, and so on. Some of these analyses were conducted and the results confirmed adequacy of the design.