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Real-Time Convolutional Neural Network-Based Star Detection and Centroiding Method for CubeSat Star Trackers


Centrala begrepp
A Convolutional Neural Network (CNN)-based approach for robust star detection and centroiding, tailored to address the challenges posed by noisy star tracker images in the presence of stray light and other artifacts.
Sammanfattning

The proposed method introduces an end-to-end training approach for a singular CNN, designed to concurrently handle star detection and centroiding. This method surpasses the centroiding accuracy and detection robustness achieved by several existing techniques.

The authors generate synthetic star images, augmented with real sensor noise and stray light, for training purposes to reduce the reliance on manual labeling efforts. A comprehensive performance evaluation of various CNN models is conducted, identifying the most suitable CNN architectures for real-time star tracker image processing.

The CNN-based method outperforms traditional star detection and centroiding algorithms in both synthetic and real-world tests, exhibiting superior resilience to high sensor noise and stray light interference. An additional benefit is that the algorithms can be executed in real-time on low-power edge AI processors.

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Statistik
The average photon arrival rate received by an image sensor over the V band is given by: n̄ = 1.085356 × 10^11 × 10^(-mV/2.5) photons/s·m^2. The probability of a pixel obtaining p photons during an exposure time T is given by: P(∫_T x(t) dt = p) = (n̄T)^p * e^(-n̄T) / p!. The pixel bit counts V(u_i,v_i) can be calculated as: V(u_i,v_i) = floor(N * QE * (2^Nbits - 1) / FWC) * (FWC / (2^Nbits - 1)), where N is the total number of photons received by the pixel.
Citat
"Trained using simulated star images overlayed with real sensor noise and stray light, the CNN produces both a binary segmentation map distinguishing star pixels from the background and a distance map indicating each pixel's proximity to the nearest star centroid." "Leveraging this distance information alongside pixel coordinates transforms centroid calculations into a set of trilateration problems solvable via the least squares method."

Djupare frågor

How can the proposed CNN-based method be extended to handle dynamic star images with varying rotation rates and exposure times

To extend the proposed CNN-based method to handle dynamic star images with varying rotation rates and exposure times, several adjustments and enhancements can be implemented: Dynamic Image Processing: The CNN model can be trained on a dataset that includes images with varying rotation rates and exposure times. This will enable the model to learn how to detect and centroid stars in dynamic scenarios. Temporal Information: Incorporating temporal information into the CNN architecture can help the model understand the movement of stars across frames. This can be achieved by using recurrent neural networks or temporal convolutional networks. Adaptive Thresholding: Implementing adaptive thresholding techniques can help the model adjust its detection criteria based on the rotation rate and exposure time of the images. This can improve the model's accuracy in dynamic scenarios. Data Augmentation: Augmenting the training data with simulated dynamic scenarios can help the model generalize better to unseen rotation rates and exposure times during inference. Real-time Processing: Optimizing the model for real-time processing by reducing inference time and computational complexity will be crucial for handling dynamic star images effectively.

What are the potential limitations of the trilateration-based centroiding approach, and how could it be further improved

The trilateration-based centroiding approach has some potential limitations that can be addressed for further improvement: Sensitivity to Noise: The trilateration approach may be sensitive to noise in the image, leading to inaccuracies in centroid calculation. Implementing noise reduction techniques or using denoising algorithms before centroiding can help mitigate this issue. Outlier Handling: Outliers in the distance measurements can significantly impact the centroid calculation. Robust estimation techniques or outlier rejection methods can be employed to improve the accuracy of centroiding. Non-linear Distortions: Non-linear distortions in the image due to optical effects or lens imperfections can affect the accuracy of trilateration. Calibration procedures and distortion correction algorithms can help mitigate these distortions. Limited Coverage: Trilateration requires distance measurements from at least three known points, which may not always be feasible in all scenarios. Exploring alternative methods like triangulation or using additional reference points can enhance the centroiding process. Dynamic Adaptation: Developing adaptive algorithms that can dynamically adjust the trilateration process based on the characteristics of the image and the distribution of stars can improve the robustness and accuracy of centroiding.

What other types of celestial objects, beyond stars, could this CNN-based method be adapted to detect and localize

The CNN-based method can be adapted to detect and localize various celestial objects beyond stars by training the model on diverse datasets and modifying the architecture as needed: Planets and Moons: By including images of planets and moons in the training data, the CNN can learn to differentiate and localize these objects based on their unique features and characteristics. Asteroids and Comets: Training the model on images containing asteroids and comets can enable it to detect and track these celestial objects in the night sky, providing valuable information for astronomical observations. Galaxies and Nebulae: Expanding the dataset to include images of galaxies and nebulae can allow the CNN to identify and locate these larger celestial structures, contributing to astronomical research and exploration. Satellites and Space Debris: Incorporating images of satellites and space debris can help the model detect and track artificial objects in space, aiding in satellite tracking and space situational awareness efforts. Transient Events: Adapting the CNN to detect transient events such as supernovae, gamma-ray bursts, or other astronomical phenomena can enhance its versatility and utility in monitoring and studying dynamic events in the universe.
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