The mission concept IRASSI is composed of five free-flying telescopes orbiting around the second Lagrange point, L2, of the Sun-Earth/Moon system. To achieve an unprecedented observation resolution, the baselines (i.e. physical separation) between each pair of telescopes must be known with an accuracy of 5 μm. To this end, a ranging system is employed to provide distance and angular measurements at micrometer-level and arcsec accuracy level between the ranging sensors located on top of each spacecraft. A crucial task in the IRASSI project is to develop a precise, real-time and robust relative positioning approach that determines the baselines between the telescope using the available measurements with the specified accuracy. In this work, a geometric snapshot method is presented that determines relative positions and attitude of each telescope using the measurement of only the current time instant. However, such snapshot methods are very sensitive to outliers or missing measurements, hence filter-based approaches are an option to be studied in future to increase the robustness of the measurements. Since filter-based approaches normally include the process dynamics, i.e., also the acceleration forces due to gravity and solar radiation pressure, the modeling level of such forces within the process model will be analyzed. Thus, a suggestion is provided regarding when and to which extent the acceleration forces need to be taken into consideration.     «

The mission concept IRASSI is composed of five free-flying telescopes orbiting around the second Lagrange point, L2, of the Sun-Earth/Moon system. To achieve an unprecedented observation resolution, the baselines (i.e. physical separation) between each pair of telescopes must be known with an accuracy of 5 μm. To this end, a ranging system is employed to provide distance and angular measurements at micrometer-level and arcsec accuracy level between the ranging sensors located on top of each s...    »