The purpose of the Optical Bench (OB) is the transference of the attitude from the extremely precise star trackers to the magnetometer field components. The OB ensures a highly mechanical stable platform for the magnetometer and the star trackers. An exhaustive thermos-mechanical design and analysis is carried out to determine and minimise any thermal gradient that could cause a shift in the relative attitude between the two systems.

The star trackers are very magnetically clean; the separation between the two instruments, Star Tracker (STR) and Vector Field Magnetometer (VFM), is about 40 cm to reduce magnetic perturbation from the STRs. The exploitation of the symmetric system has resulted in a cylindrical tube holding the VFM sensor, minimising transversal thermal gradients. Emphasis has been on the matching of material parameters, the use of isostatic support interfaces, and a detailed analysis of the loads. The instruments are calibrated as standalone, and once integrated in the OB, an inter-calibration and system verification is carried out to determine the relative orientation between the VFM and STR and to verify that the stability is as required.