Electron Density Specification in the Inner Magnetosphere From the Narrow Band Receiver Onboard DSX

Electron density plays an important role in the study of wave propagation and is known to be associated with the index of refraction and radiation belt diffusion coefficients. The primary objective of our investigation is to explore the possibility of implementing an onboard signal processing algorithm to automatically obtain electron densities from the upper hybrid resonance traces of wave spectrograms for future missions. U‐Net, developed for biomedical image segmentation, has been adapted as our deep learning architecture with results being compared with those extracted from a more traditional semi‐automated method. As a product, electron densities and cyclotron frequencies for the entire DSX mission between 2019 and 2021 are acquired for further analysis and applications. Due to limited space measurements, a synthetic image generator based on data statistics and randomization is proposed as an initial step toward the development of a generative adversarial network in hopes of providing unlimited realistic data sources for advanced machine learning. Plain Language Summary Electron density is the most important fundamental plasma parameter, however, it is very difficult to directly measure in situ due to spacecraft potential. A convolutional neural network (CNN), developed to recognize features from biomedical images, has been adapted to pull out the resonance traces from space wave receivers automatically specifying densities along satellite orbits. The comparison between computer vision based on a CNN and human vision based on a semi‐automated extraction is demonstrated in this paper. With additional development and refinement, our proof‐of‐concept study may be matured to a level suitable for incorporation into onboard signal processing units to reduce human labor and human‐in‐the‐loop induced operational errors during future space missions. Key Points U‐Net can automatically extract plasma frequencies from in situ wave receivers after it is trained from spectrograms with accurate labels Electron densities and cyclotron frequencies for the entire DSX mission are published for other research and applications