ELECTROMECHANICAL DESIGN OF A DRIVE MECHANISM FOR THE ROTATION OF THE SPECTROMETER WHEEL INSIDE MEDET EXPERIMENT

One of the experiments on board of the Material Exposure and Degradation Experiment on Eutef (MEDET) consists of a Spectrometer. The aim of the experiment is to study the degradation of the properties of optical materials exposed to near earth orbit space environment. The samples of optical materials under investigation are placed on a rotating wheel. A drive mechanism is used to rotate the wheel and position each sample in front of the optical diffuser and the spectrometer sensor. The first step of the design was the choice of the components and the choice of the materials for the mechanical parts. Then, the detailed mechanical design of the assembly has been carried out. The mechanism has been designed in order to be integrated inside MEDET. This has posed constraints in terms of geometry and power budget for the components. A structural analysis of the drive mechanism assembly has been carried out to ensure the integrity of the mechanism during launch. The sample wheel is driven by a stepper motor that has been controlled by a closed-loop algorithm. The choice of the type of control has been driven by in orbit reliability considerations. A breadboard of the mechanism has been assembled in ESTEC laboratory to perform a drive control test. Challenges of the design have been the very limited time available for the overall concept and validation and the limited resources for the project that has been classified as a low cost experiment. The work has been carried out in the ESTEC laboratories with a close collaboration between mechanical and electrical engineers of the testing and material department