Theta/Phi fiber positioner for the SDSS-V survey

Theta/Phi fiber positioner for the SDSS‑V survey

SDSS-V is an all-sky, multi-epoch spectroscopic survey that will yield over 6 million objects during its five-year observing-time. Using SDSS’s existing and anticipated new facilities at Apache Point Observatory (New Mexico) and Las Campanas Observatory (Chile) SDSS-V will survey the entire sky using rapid and repeated observations, mapping Local Volume galaxies and black holes.

Instead of SDSS’s classic plugplate system, SDSS-V will use a new, custom-built robotic positioning system co-designed by the Ecole Polytechnique Fédérale de Lausanne (EPFL) and MPS, and manufactured by MPS. These positioners will allow rapid configuration of the fibers.

In aiming to meet stringent accuracy specifications of less than 2.5 µm repeatability error for a patrol area of 44.8 mm of diameter, a dedicated design guarantying a play free operation has been developed. A total of 1200 units have been delivered. They will be operating on the 2 telescopes.



    Diameter :21,4 mm
    Diameter covered by the fiber :44,8 mm
    Total length :265 mm
    Motor drive - Theta arm :1 Faulhaber Brushless 0620 motor with 1024:1 reduction gearhead
    Motor drive - Phi arm :1 Faulhaber Brushless 1218 motor with 1024:1 reduction gearhead
    X-Y positionning accuracy :< 5 µm
    Repeatability : < 2.5 µm
    Inclination of the fiber relative to the X-Y plane : < 0.2 RMS
    Theta and Phi arms rotation :370°
    Life cycles :300'000 cycles


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