For the PFS instrument, the lights from about 2400 astronomical objects are designed to be delivered through long fiber cable from the prime focus of the telescope to the spectrograph modules on the fourth floor in the dome building. This fiber cable subsystem, which is about 65m long in total, consists of 3 parts: (1) short cables accommodated into the Prime Focus Instrument at the prime focus and positioned to astronomical objects, (2) short cables as slit input in the Spectrograph Modules, and (3) long cables from PFI to Spectrographs.
The fiber cable subsystem is being developed mainly by Laboratório Nacional de Astrofísica (LNA) in Brazil. To keep the image quality as well as possible, we have been carried out various studies: optimizing procedure of polishing fiber edges and cable connection, prototyping the long cables, and so on.
In this August, one of the fiber cable assembly as the slit of Spectrograph was delivered from Brazil to Laboratoire d’Astrophysique de Marseille (LAM) in France. The slit assembly has hundreds of fibers in line (see the below photo): about 600 fibers connected to the long cables from Prime Focus Instrument and 16 fibers connected to external light source for engineering.
As shown in the below photo, fibers are routed from connector part to from slit part, along the top and the bottom of the Spectrograph, not to cut in the light path in the Spectrograph. After the aiming angle of fibers and image quality were tested, the slit assembly was shipped to LAM.
(Photo of the fiber slit assembly of the Spectrograph Module. Fibers are routed along the top and bottom of the Spectrograph. Dr. Antonio C. de Oliveira is testing the slit prior to shipping.)
Delivered fiber slit cable at LAM will be tested using the engineering cables with light sources, and then integrated into Spectrograph Module.