On the Radiometric Calibration of Optical Hardware-in-the-Loop Stimulators

Optical stimulators are essential for performing validation and verification of spaceborne optical systems, allowing realistic, hardware-in-the-loop testing under controlled conditions. These facilities bridge the domain gap between synthetic image rendering and real mission data, ensuring a close-to-real evaluation of image processing algorithm performance. An open challenge in their use is the reproduction of radiometric-equivalent images that faithfully replicate in-space acquisitions. This work presents a detailed methodology for the radiometric calibration of optical stimulators, enabling the high-fidelity emulation of both resolved and pointwise objects. The proposed methodology is applied to two different testbeds and validated using an industrial camera and a high-technology-readiness-level star tracker. Experimental results demonstrate the accuracy of the proposed framework in reproducing realistic scenes, including detailed hardware-specific optical effects that are often beyond the scope of conventional rendering tools.