Design and verification of the narrow angle sensor for Tianwen-2
Abstract
<p indent="0mm">The narrow angle sensor (NAS) is a dual-purpose payload designed for both scientific research and engineering functions in the Tianwen-2 small celestial body exploration mission. This instrument is engineered to image small celestial targets (e.g., asteroids, comets) and stellar references, enabling autonomous navigation capabilities such as inertial attitude determination, optical target acquisition, and line-of-sight tracking during spacecraft positional transfer, approach, and rendezvous maneuvers. During proximity operations, NAS acquires high-resolution surface imagery of the target body. These images are primarily employed for terrain-relative navigation (TRN) landmark generation to support precision guidance, while simultaneously providing datasets for scientific objectives such as spectral reflectance analysis and target characterization studies. The sensor incorporates a compact, long-focal-length, large-aperture zoom optical system as its core. The focusing mechanism corrects optical aberrations across varying object distances, while the filter wheel facilitates the switching of observation channels and protects the CMOS image sensor from direct exposure to high-intensity light. The payload features high sensitivity, high resolution, high accuracy, and multi-spectral capabilities. This study primarily introduces the composition, operational modes, and design scheme of NAS, and describes the ground calibration and verification results of the instrument.</p>
