Image Desaturation for SDO/AIA Using Deep Learning

The Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) (launched in February 2010) provides uninterrupted full-disk solar images over 10 wavebands. In the case of violent solar flares, saturation would happen to SDO/AIA images in their core regions, which leads to signal loss, hindering us to understand physical mechanism behind solar flares. This paper introduces a deep learning based image restoration model which can recover signal of saturation region by referring to other normal/valid region within an image. The proposed model, namely PCGAN, combines partial convolution (PC) and conditional generative adversarial network (GAN). The PC module was originally designed for image inpainting, for repairing images with scratches and holes. In addition, a new comprehensive loss function consists of an adversarial loss, a pixel reconstruction loss, a gradient loss, a perceptual loss, a style loss and a total variation loss. Moreover, for validating the proposed model, a new dataset consisting of paired saturated and normal SDO/AIA images is established. Experimental results demonstrate that the proposed PCGAN can get appealing desaturated solar images with respect to both objective and subjective validations.