As part of the preparation for the arrival of the MUSE instrument to the VLT, it was required to adapt the hosting
telescope (UT4) guide probe, to increase its back focal length. This is to allow enough space for the later deployment of
the MUSE Adaptive Optics module GALACSI, in-between the telescope adapter rotator and the instrument itself. The
UT guide probe is a critical component for the successful operation of the telescope, so its modification to increase the
telescope’s back focal length, while maintaining full compatibility with the existing operation model and other hardware,
was rather demanding.
The design, manufacture, assembly and test for the new supporting arm in the UT guiding probe is presented. It mixes
the use of novel materials (HB-CESIC® for the mirrors substrates) and state of the art manufacturing techniques (3D
printing mould production and rapid casting for the support structure), which allow producing easily a high performance
subsystem. Characterization of the system prior delivery to the telescope, its integration in the UT and results after
commissioning is presented. Its successful implementation has validated new manufacturing techniques that may prove
very useful for future instruments development.