Low-Illumination Image Enhancement in the Space Environment Based on the DC-WGAN Algorithm

Owing to insufficient illumination of the space station, the image information collected by the intelligent robot will be degraded, and it will not be able to accurately identify the tools required for the robot’s on-orbit maintenance. This situation increases the difficulty of the robot’s maintenance in a low-illumination environment. We proposes a novel enhancement method for images under low-illumination, namely, a deep learning algorithm based on the combination of deep convolutional and Wasserstein generative adversarial networks (DC-WGAN) in CIELAB color space. The original low-illuminance image is converted from the RGB space to the CIELAB color space which is relatively close to human vision, to accurately estimate the illumination image, and effectively reduce the effect of uneven illumination. DC-WGAN is applied to enhance the brightness component by increasing the width of the generation network to obtain more image features. Subsequently, the LAB is converted into RGB space to obtain the final enhanced image. The feasibility of the algorithm is verified by experiments on low-illuminance image under general, special, and actual conditions and comparing the experimental results with four commonly used algorithms. This study lays a technical foundation for robot target recognition and on-orbit maintenance in a space environment.

Research on the Lissajous Trajectory Transfer of Large Area Mass Ratio Solar Sail Spacecraft

Considering that the solar sail spacecraft working in the Lissajous orbit will be affected by the shadow of the earth or the solar wind, which sometime makes the spacecraft unable to work, we try to use the solar light pressure as the thrust to carry out the Lissajous orbit transfer in advance. Because the solar pressure parameters(cone angle, clock angle and solar pressure factor) will change the position of the libration points, we propose the idea of splicing the old and new libration point manifolds to transfer the escape spacecraft to the new Lissajous orbit to achieve orbit maintenance. The simulation results show that besides changing the cone angle and the solar pressure factor, the clock angle can also achieve orbit transfer, and the influence of the solar pressure factor on the periodic orbit is greater than the other two. This study provides a reference for the solar sail spacecraft in the aspects of periodic orbit transfer, orbit maintenance and avoidance of the earth's shadows.