Remotely acquired spectroscopy measurements of human made space objects often contain a reddening of their reflectance spectra when compared to ground truth measurements of the space objects in a pristine state. This reddening is characterized by either a relative decrease in reflectance of shorter (i.e. “bluer”) wavelengths or a relative increase in reflectance of longer (i.e. “redder”) wavelengths. Despite the prevalence of spectral reddening in spectroscopy signatures of space objects, its physical drivers remain undefined. Theories for the cause of reddening range from spectral mixing of spacecraft materials over the telescope’s integration time to breaking of element bonds by incident energy to absorption of space-borne particles into the space object’s exposed surface layers. Many theories claim that reddening is a process that is driven by the space environment such that materials undergo healing when returned to Earth’s atmosphere. During a recent laboratory-based aging campaign performed on emerging spacecraft materials, it was found that reddening that was caused by electron irradiation persisted even after exposure to the Earth’s atmosphere. In this study, we examine the potential physical causes on three different spacecraft Polyimide Pyromellitic Dianhydride (PI/PMDA) materials that exhibited reddening using radiative transfer theory. The radiative transfer model predicts that the PI/PMDA materials in this study become increasingly conductive over the Ultraviolet (UV) through Shortwave Infrared (SWIR) spectral range due to an increased density of free-electrons that are available to interact with incident photons. This increased conductivity leads to increased spectral absorption over the UV through SWIR, with accelerated absorption occurring at shorter wavelengths such as the UV resonance feature of the PI/PMDA materials.
Understanding Spectral Reddening of Electron Irradiated Spacecraft Kapton Polymers Using Radiative Transfer Theory
J Astronaut Sci
2025-07-08
Article (Journal)
Electronic Resource
English
Electron irradiation , Bidirectional reflectance distribution function (BRDF) , Spectroscopy , Space weather , Materials Chemical Sciences , Physical Chemistry (incl. Structural) , Engineering , Aerospace Technology and Astronautics , Space Sciences (including Extraterrestrial Physics, Space Exploration and Astronautics) , Mathematical Applications in the Physical Sciences
Conduction processes in Kapton H irradiated by an electron beam
Tema Archive | 1983
|British Library Online Contents | 2001
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