In order to reach a micrometer accuracy, a suitable model of a space telescope needs to be developed and validated through calibration. Since high velocity is not required in such an application, the dynamic effects can be neglected and only geometric and/or static calibration has to be considered. Moreover, measurements for calibration are performed in a clean room under controlled pressure, temperature and humidity conditions to minimize the influence of the non-geometric errors. Thus, two possible static inaccuracy sources are identified and modelled: one from the deformation of the mobile platform and the other resulting from the behaviour of the flexure joints. Their influences on the final accuracy of the telescope are compared through results of calibration using an accurate measurement system of photogrammetry. Results show that the flexure joints can be modelled by perfect spherical joints due to the small workspace of the telescope. As for the mobile platform deformation, the developed models allow us to explain how the model errors are directly accounted in the parameter identification during the experimental calibration. This results in different sets of identified parameter values which all enable a good positioning accuracy. Those differences are explained and results of calibration allow a proper choice of the most suitable model for the telescope. Considering this model, a positioning accuracy of some micrometers is finally reached.
