Scheme design and key technology verification of Narrow Angle Sensor for small body mission

Abstract

<p>   In small body exploration mission, the uncertainty of the target characteristics and the special weak gravitational environment put forward higher requirements for the optical autonomous navigation accuracy of the probe and the detection ability of the navigation sensor. Narrow Angel Sensor(Hereinafter referred to as NAS), as the key instrument of China’s first small body exploration mission, has both optical autonomous navigation function and scientific observation ability, and it must give consideration to both near and far, and achieve breakthroughs in dynamic range, detection sensitivity, pointing measurement accuracy, angular resolution and spectral observation ability. The specific performance is as follows: To capture and track Near Earth Asteroids 2016HO3 from tens of thousands of kilometers, NAS is required to have the ability of point target detection, and the detection sensitivity is better than MV10, and  the accuracy of pointing measurement is better than 1 ″. As the probe approaches the target, NAS must be able to clearly image the shape and surface texture of 2016HO3, so as to obtain the motion parameters such as the spin axis and rotation period of the target. In remote sensing and descending stage, the mission requires NAS to be able to carry out global centimeter scale and landing area millimeter scale multi-spectral observation of the target, and optical navigation uses high-resolution images to construct landmark feature library, so as to realize terrain relative navigation; meanwhile, the image is used to provide data support for the scientific research of the target topography, spectral characteristics and surface material composition analysis.</p> <p>   NAS adopts split design, and the detector part is composed of front door, baffle, focusing optical system, filter wheel, image processing circuit, and motor drive circuit, the algorithm is implemented in the image navigation processing unit. The prototype of the instruments has been developed, and the function and performances such as MTF, detection sensitivity, pointing measurement accuracy etc were verified. The instrument achieved expected design objectives,  and can meet the requirements of optical autonomous navigation and scientific observation for China’s small body exploration mission.</p>