High-Density Fiber Positioner Module
Next-generation massive multi-object spectroscopic instruments require more optical fibers to be positioned within focal planes. To support this evolution, MPS has developed a new-generation fiber positioning platform with a 6.2 mm center-to-center pitch.
The system brings together 63 theta-phi fiber positioners in a compact triangular module. Each positioner is directly integrated into the module and driven by two independently actuated rotating axes, allowing precise movement of the optical fiber within a highly dense mechanical layout.
This development builds on several generations of MPS fiber positioner technology and marks an important step toward more integrated focal-plane architectures. By combining miniaturization, modularity and positioning accuracy, the system is designed for future astronomical instruments requiring high fiber density and reliable target acquisition.
| Module capacity | 63 positioners per triangular module – module of 74 mm edge |
| Theta & Phi arms length | 1.8 mm |
| Range of motion | Theta: -5° to +365° / Phi: -5° to +185° |
| XY positioning repeatability | < 5 µm RMS |
| Maximum tilt error, module mount to fiber tip | < 0.5° |
| Drive mechanism | 4 mm BLDC gearmotors |
| Fiber bend radius, tip to connector | > 50 mm |
| Operational lifetime | > 300 000 move cycles |
The new high-density fiber positioner module from MPS is designed as a compact functional unit for high-density focal planes. Instead of mounting each fiber positioner individually on the focal plate, 63 small positioners are incorporated directly into a single module.
This approach simplifies the integration process. Complete modules can be assembled, tested and handled before installation, reducing the complexity associated with large focal-plane assemblies. At instrument scale, this means that many individual positioning mechanisms can be managed through a smaller number of module-level units.
The modular concept also leads to easier maintenance. When intervention is required, the system can be approached at module level rather than only at individual positioner level.
Each module also integrates its control electronics on the rear side, contributing to a compact architecture and reducing the need for separate external control assemblies close to the focal plane.
High positioner density only brings value if each fiber can still be placed accurately and reliably. The MPS module combines a compact mechanical design with an XY positioning repeatability below 5 µm RMS, supporting precise target acquisition across densely populated focal planes.
The independent theta-phi architecture allows each rotating axis to be controlled separately. This supports predictable fiber tip movement and simplifies positioning control, even within the compact 6.2 mm pitch.
Controlled angular tilt is another important design parameter. By limiting the tilt between the module mount and the fiber tip, the positioner helps reduce focal ratio degradation and preserve optical throughput to the spectrographs.
The system is also designed with fiber handling in mind, maintaining a fiber bend radius above 50 mm from tip to connector. Combined with an operational lifetime above 300,000 move cycles, this supports the reliability expected from large-scale astronomical instruments.
