Luminous Efficiency Determination of Spacecraft Materials in Ground Test Facilities

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This paper reports the approach to determine the luminous efficiency of spacecraft materials experimentally. The idea is that knowing the luminous efficiency of spacecraft materials allows for deriving mass estimates from observation data linking meteor science methods to man-made artificial meteors. This way, observation data from airborne missions and known ground-based meteor observation networks become a versatile tool to analyze destructive spacecraft entry. Material samples were scaled to a typical re-entry condition. The authors recently developed a method to determine the radiant flux in the passbands U, B, and V and the corresponding color indices. The measured mass loss during the experiment is used to determine the luminous efficiency τ for the different passbands. These values are reported for three different materials under flow conditions corresponding to two trajectory points at altitudes of 70km and 65km in a typical decaying re-entry orbit. The resulting luminous efficiency values are of the order 10-5, which is about two orders of magnitude lower than meteoroid efficiencies. The found data is applied to fragments observed during the CYGNUS OA-6 observation campaign. The mass loss was extrapolated for the entire duration of the re-entry resulting in a mass of around 68-80% of literature values for the mass at the entry interface.