POSM: a new concept for fiber positioning

The Gemini/Subaru WFMOS project has given the stimulus for considering new concepts for massively multiplexed fiber positioning schemes. The problem of acquiring many thousands of objects within a ~1.5° field at Subaru's ~f/2 prime-focus station represents a challenge to normal concepts of fiber positioning. Solutions usually involve imposing limits to the patrol field of each fiber. Using this simplification, a new concept is proposed which moves objects onto a fixed array of fibers rather than moving the fiber themselves. Such a scheme may simplify the manufacturing and assembly processes and may result in a more robust solution compatible with the challenging prime-focus environment. We describe the POSM concept and present an initial opto-mechanical layout.