Objective   The space-based space target detection system based on the micro-satellite has the advantages of large-scale high-frequency observation and low cost, so it has developed rapidly. At present, foreign space-based space target detection systems have adopted a large number of micro-satellite platforms, such as Canadian MOST satellite, Sapphire satellite, NEOSSat satellite, STARE satellite, etc., with a payload weight of tens of kilograms, the weight of the whole satellite is about 100 kg, and the faint target detection ability can usually reach more than 13 magnitude. The article has designed and developed a compact, large field of view (FOV) and high-sensitivity optical camera for space target detection, which has a detection magnitude of more than 13 Mv, a detection FOV of 8°×8°, and a weight of 5 kg. It can be widely deployed on micro-satellite platforms or hosted on large satellites. It can give full play to the advantage of cluster detection, realize the wide-range, high-sensitivity, and high-frequency detection of faint space targets such as space debris and asteroids, and provides high real-time data support for space debris collision warning and asteroid research.

  Methods   A compact, large FOV and high-sensitivity optical camera is built in this paper. Aiming at the application requirements of lightweight, small size, large field of view and high sensitivity of the detection camera, the paper comprehensively optimizes the optics, structure, electronics and stray light suppression to achieve the best detection capability. In terms of optics, a large field of view and small F-number optical lens has been designed and realized. During the optimization process, the lens size is strictly controlled, and the low-density glass material is optimized. On the premise of ensuring the optical performance, the lightweight and miniaturization is realized, and the optical system field of view is 8°×8°, the optical system length is 280 mm and optical energy concentration is 90% (Fig.6). In terms of structure, an integrated long lens tube structure is designed and realized to ensure that the lightweight lens has high structural stiffness and dimensional stability, and the lens tube weight is less than 1.8 kg. In electronics, the combination of high-sensitivity detector and high-integration low noise circuit is used to achieve good noise suppression and lightweight. In the aspect of stray light suppression, the extinction structure is designed at the key part of the lens barrel, the light shield with chamfer is designed, and the ultra-black coating is sprayed inside to achieve good stray light suppression effect.

  Results and Discussions  The lightweight and highly sensitive optical camera has been developed and integrated (Fig.7), with a total weight of 4.9 kg. Through the ground observation test, it is verified that the detection capability of the camera is 13.2 Mv.

  Conclusions  With the increasing frequency of space activities, the space situational awareness is crucial for the safe development and utilization of space. Space situational awareness based on micro-satellite is an efficient and cost-effective approach. Aiming at the application requirements of space target detection on micro-satellite platform, a lightweight and highly sensitive optical camera for faint target detection was designed and developed, with a weight of 5 kg and a detection FOV of 8°×8°. It was verified by ground tests that the detection ability was better than 13 Mv. The camera can be widely deployed on micro-satellite, and can detect faint space targets with high sensitivity and high frequency, providing high real-time data support for space debris research and collision warning.