ARIEL [ESA], the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, is one of the three candidate missions selected by the European Space Agency (ESA) for its next medium-class science mission due for launch in 2028. The goal of the ARIEL mission is to investigate the atmospheres of several hundred planets orbiting distant stars in order to address the fundamental questions of how planetary systems form and evolve. The main activities of IA – instrumentation in ARIEL together with the OGSE team led by Oxford University, were associated with the design of part of the OGSE system, associated with the illumination module and reference detector subsystem working in the Visible /Near Infrared part of the spectrum. The reference detector function is to monitor the light source fluctuations and to provide source stability data required to detrend the results from the ARIEL instruments when operating in vacuum and cryo conditions.