Michael Schmidt, Technical University of Munich, Munich, Germany, Mathis Blossfeld, DGFI German Geodetic Research Institute, Munich, Germany, Klaus Börger, German Space Situational Awareness Centre (GSSAC), Uedem, Germany, Ehsan Forootan, University of Hohenheim, Institute of Physics & Meteorology, Hohenheim, Germany, Andres Calabia, Nanjing University, School of Remote Sensing and Geomatics Engineering, Nanjing, China, Fabricio Prol, German Aerospace Center (DLR), Neustrelitz, Germany and Benedikt Soja, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States