Robot configuration for distortion measurement of spacecraft reflectors during in-orbit phase

Abstract

Communication satellite carries large size deployable reflectors. These reflectors are assembled and launched in stowed configuration and deployed in-orbit. Precise positioning and alignment of the reflector surface with the spacecraft structure is an evolved process. Small amount of misalignment may result in serious repercussion on the entire mission objective. Distortion due to launch loads and space environment affect the alignment of reflectors. Spacecraft level measurement and simulation are carried out during ground level testing to predict in-orbit performance. This paper proposes the development of robotic arm which aids vision based inspection system to measure the possible misalignment of reflectors during its in-orbit phase. The novelty of this study is configuring a space robot to capture multiple images of the reflector associated with reflective markers. These images are then registered and matched to evaluate three-dimensional (3D) coordinates of the reflective markers. Any deviation in 3D coordinates of these markers is indication of the possible distortion on reflector. It is found that distortion measurement would need fewer images, if it is shot by camera held by a seven axis manipulator position along the circular trajectory (orthogonal to the axis of reflector).