Development of an Optical Sensor Simulator for Space-Based Debris Surveillance

Since the 2007 Chinese anti-satellite missile test, Space Debris has become a dominating talking point within the space community, prompting initiatives like the European Space Agency's Space Situational Awareness (SSA) program – started in 2009 - to track and catalogue fragments and leftover upper stage structures. This study aims to develop a tool capable of simulating images of debris captured from a satellite operating from a Sun-synchronous orbit, to develop software prior to launch that enables the onboard processing of this particular image data. To accomplish this objective, a Python-based tool was developed following an object-oriented programming approach. The tool integrates crucial data sources, including the GAIA Star Catalogue, which provides accurate positions and brightness information of stars, and the SPOOK object propagator for propagation of synthetic debris objects. Realistic Cosmic Ray maps were also derived from data on proton fluxes within the South Atlantic Anomaly. The image simulator is designed for utilization of both CCD and CMOS sensors, tailored for a Newtonian-type telescope. It incorporates a Point Spread Function to simulate photon diffraction on the pixel wells of the sensor, and permits us to generate distinct "point" and "streak" features. The simulator effectively accounts for various sources of noise, including poissonian-like events such as atmospheric dispersion and straylight of photon sources, as well as non-poissonian noises like readout and reset noise. This model was compounded by an in-depth analysis and modelling of defective pixels, through reverse engineering of data from both types of sensors. Finally, an optical performance model is also integrated to predict and simulate photon collection from artificial objects based on their albedo, size, shape, temperatures and dimensions. The results demonstrate the effectiveness of the developed software through 15 validation scenarios, with an additional two scenarios recreating real-life pointing and tracking situations for both CCD and CMOS sensors. These simulations have yielded significant improvements in background noise modeling and Signal-to-Noise Ratio (SNR) approximation. The outcomes provide a foundation for the development of onboard software for debris tracking and segmentation, which would enable Airbus’ projects to process data directly onboard space-based telescope without the need to transmit large image files.