Assembly of positioner module is in progress / ファイバー配置モジュール組み立て中

PFS instrument catches light from about 2400 astronomical objects using fibers paved on the focal plane at the prime focus of the Subaru telescope, and each fiber is positioned by 2-staged actuator called “Cobra” (). As talked in the previous posts, 57 assemblies of Cobra positioners and fibers are integrated to one module, which is mounted to the optical bench. Since mass production of fiber positioners started early this year, the integration of the first module has been in progress at Caltech, the US, where engineers from Caltech and NASA/JPL who expert on positioners, and those from LNA (Laboratório Nacional de Astrofísica, Brazil) in charge of fiber parts, are working together.
In this article, we will talk about assembly of Cobra module, spotlighting positioners.

A module has 2 lines of Cobra positioners controlled using 2 electronic board. In the below video, 28 positioners in one line are moved simultaneously using one board. The fibers will be assembled in the future.

In parallel with development of the first Cobra module, the software to control positioners has been developed by team from NASA/JPL (Jet Propulsion Laboratory). To cover entire field of view, each fiber patrol area, where a fiber moves around, overlaps slightly with neighboring fibers. Hence, their collision potentially happens. The software is being developed following discussions how to move positioners to reduce the possibility of collision, and how to calibrate positioners to converge them to a target position well. Simulations of collisions has also been carried out.

[ Discussion on strategy of Cobra calibration.  From left:  Dr. Johannes Gross (Engineer, NASA/JPL), Prof. Daniel Reily (Caltech) ]

Completed modules will be shipped to ASIAA (Academia Sinica, Institute of Astronomy and Astrophysics) in Taiwan, where the modules will be mounted to the optical bench, and about 8-meter long fibers will be routed inside of main structure.  Because of tight spacing, devoting great care is needed to integration work not to damage the instruments. Therefore, ASIAA team have made full-size mock-ups to practice the assembly.

 [ Mock-up of Cobra module (full-scale) ]

[ Demonstration of assembly of Cobra modules by ASIAA team. A guide rail is used for mount. From left, Mr. Hsin-Yo, Chen (Engineer), Mr.  Yin-Chang Chang (Engineer), and Prof. Shiang-Yu Wang ]







(コブラモジュールの組み付けの練習の様子。まっすぐ組み立てるためにガイドを使う。左から:中央研究院天文及天文物理研究所の陳心躍 (チェン シンヨウ) 技術職員、張蔭昌 (チョウ インチャン)技術職員、王祥宇 (ワン シャンユー) 教授)

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