Speaker
Description
The concern raised by astronomers due to undesired acquisitions of space debris and satellites streaks in astronomical images determined a growing interest in so called Dark and Quiet Skies policies over the last years. Space agencies, international organizations and national governments are issuing new recommendations and laws aimed at ensuring
that the apparent brightness of space objects is below a certain threshold, typically recognized as V magnitude not below 7. Although this common requirement does not take into account the several factors that affect an object brightness, it demands for methods aimed at evaluating an object brightness both in the design and operational phase. Evaluating a satellite brightness in the early design phase enables the implementation of mitigation strategies at material level to reduce brightness, if necessary, whereas an assessment of brightness in the operational phase, once in orbit, allows the scheduling of attitude maneuvers to reflect sunlight towards preferred directions. In any case, the development of tools for evaluating a satellite brightness is required. We present a comprehensive approach to brightness evaluation developed under the ESA contract BILAR, which uses both real optical and simulated measurements to provide an assessment of a material brightness. Real measurements are obtained through observations in different photometric band, from the near ultraviolet to the near infrared. Simulated measurements are obtained through a dedicated digital twin that enables the evaluation of a satellite brightness under several configurations, as a function of different attitudes, materials characteristics and orbital conditions. The latter approach is further improved by the application of experimental BRDF measurements of typical space materials, enhancing the achievable characterization level. The entire approach, including real observations,experimental measurements and the digital twin will be presented in this paper.
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