Statistics – Methodology
Scientific paper
Jan 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002iaf..confe.436m&link_type=abstract
IAF abstracts, 34th COSPAR Scientific Assembly, The Second World Space Congress, held 10-19 October, 2002 in Houston, TX, USA.,
Statistics
Methodology
Scientific paper
reflector consists of a system of cables, a metallic mesh surface, and a support structure. To obtain the desired surface accuracy, we performed the following process. (1) Design a highly rigid surface cable network system that uses an elastic support cable network system to improve manufacturing accuracy and prevent errors in the support structure from degrading the cable network system. (2) Strictly control manufacturing accuracy to minimize surface adjustment after manufacturing. (3) Improve the accuracy of measurement and adjustment operations under the gravity environment. Two cable network models and one cable-mesh model, each of which is about 2 m in diameter, were designed and fabricated to validate our design methodology. We controlled and inspected the accuracy of cable length at the desired cable tension. The analysis model predicted the surface accuracy of better than 0.4 mmRMS with the cable manufacturing error of less than 0.04 mm. However, cable the manufacturing error obtained was 0.1 mm, and the resulting surface error (measured) was 1.0 mmRMS. We found that a surface accuracy of better than 1.0 mmRMS can not be achieved easily without any adjustment. To estimate the errors in ground measurement, we measured surface shape under the micro-gravity environment established within a jet airplane, a Gulfstream II. The results show that the calculated surface shape contains estimation error of 0.3 mmRMS. The other cable network model used a balloon as the support structure to demonstrate the stability of the cable network structure against deformation of the support structures. The surface error was held to under 1.0 mmRMS when the support structure deformed by 30 mmRMS. The third model had a mesh surface to evaluate electrical performance. Radiation patterns were obtained by a near field range measurement system. A full-scale Ku band antenna reflector, whose diameter is around 10 m, has been designed and analyzed. The number of cables is seven times of the number of cables in the conventional S-band antenna reflector. An equilibrium shape analysis confirms that the surface error of better than 0.4 mmRMS can be achieved. reliability in defining the difficulty index of ground deployment testing for large deployable antennas. The relationship between the index value and the accuracy of results from ground deployment testing has been estimated by deployment testing of a simple deployment truss structure under both full and micro- gravity conditions. We found that the deployment reliability of a deployable structure can not be evaluated with adequate accuracy if its size exceeds 10 m.The structure must be divided into modules ofappropriate size. Basic studies on inflatable structures and flexible patch elements for future large aperture, sophisticated direct radiation array antennas are underway. Inflatable structures, which consist of rigidized materials and flexible patch elements for feed elements, are interesting candidates. In addition to these studies, distributed sensor/actuator location, non-linear vibration control method, and optimum design methods are also being addressed. They are key technologies for high performance, highly stable, and re-configurable antenna systems.
Harada Satoshi
Ishikawa Hironori
Meguro Akira
Mizuno Hideki
Tsunoda Hiroaki
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