Simulation and Measurement of Multispectral Space Debris Light Curves

Kurzfassung

The accumulation of space debris has become one of the greatest threats facing the space industry to date. Through an increasing amount of objects deposited in Earth's orbit, such as rocket bodies, defunct satellites and general debris fragments, space missions are exposed to a growing risk of collisions. Moreover, the recent surge in commercial space applications is expected to further contribute to the problem. At the Institute of Technical Physics of Deutsches Zentrum für Luft- und Raumfahrt (DLR) in Stuttgart, resident space objects are monitored using a number of telescopes through active laser and passive sunlight illumination. Due to the high altitude and relatively small size of the objects they generally appear as unresolved points in photometric images. An object's temporal variation in brightness is referred to as a light curve and implies key information concerning the object's shape, material composition and rotation. Recovering these parameters from light signals is not trivial and it is anticipated that additional information provided by multispectral observations will contribute to a more reliable characterization of space debris. This research covers the development of a physically based simulation to model multispectral light reflections from space debris. The software is targeted towards ground-based observations and is expected to form an integral part in facilitating future strategies for comprehensive collision avoidance and space debris removal. Both passive light curves and laser ranging measurements are simulated using three-dimensional satellite models. To improve the accuracy of simulations, spectral lab measurements of common space materials are incorporated into the render. Further, the process of gathering reference measurements using the DLR's 43 cm telescope at the Uhlandshöhe Forschungsobservatorium is presented. For the comparison between synthetic and empirical light curves, a detailed calibration of the optical system is performed. The validity of the light curve simulator is confirmed the on the basis of recordings obtained from radar calibration targets. Finally, simulated data is used to study benefits of multispectral observations for characterization and parameter estimation from space debris.