Design and implementation of a low-light spectrometer for space debris characterization

Abstract

Orbital congestion due to space debris is continuously increasing. In the current absence of significant mitigation and removal efforts, the best option is precise tracking and trajectory prediction of debris objects. Avoidance maneuvers can minimize damage to satellite infrastructure, but they consume fuel and energy, hence, reducing the operational lifetime of satellites. More detailed information must be gathered through space debris observation, to minimize these maneuvers by improving the collision prediction accuracy.Reflectance spectroscopy is a method, where the observed object reflects sunlight and by subtracting the known source spectrum, its surface reflectivity is determined. By comparison to laboratory measurements of typical spacecraft materials the debris’ materials are identified, improving the quality of their surface-to-mass ratio estimation and the prediction accuracy of orbital trajectories. However, low light conditions and fast moving objects require high-precision tracking and high sensitivity of the spectrometer.This thesis investigates the development of a spectrometer optimized for ground-based reflectance spectroscopy of space debris. By analyzing the reflected sunlight, the spectrometer enables the identification of surface materials. The prototype, designed for low-light conditions, is tested at the optical ground station of the MPEI in Vienna and validated with the known spectra of stars, achieving a 3 % calibration error. It is demonstrated that nightly calibration runs further reduce that error. For the observation of Polaris, a magnitude 2 star, an exposure time of 7 minutes is necessary to achieve an acceptable SNR. A nonlinear spectral resolution varying between 7 nm and 42 nm for the calibrated spectral range of 400 to 900 nm is achieved. A first observation of an artificial object in MEO is successfully conducted, but cut short due to a cloud obstructing the view during exposure. The implemented spectrometer and the presented methodology for implementation, calibration and evaluation provide a solid foundation for reflectance spectroscopy of space debris and will be used for future work in the hosting project SpecTrackular.