2021年12月26日,5米光学02星在太原卫星发射中心成功发射,星上装载的主要载荷之一—热红外相机采用8000元长线阵长波红外探测器推扫成像,可以获取星下点地面像元分辨率优于16m、噪声等效温差小于0.1K@300K、幅宽大于115km的7.7μm~10.5μm谱段热红外影像。相比国内外在轨热红外遥感相机,该相机同时实现高分辨率、高灵敏度和大幅宽观测,能够实现空间和温度的高效率精细化探测,具有明显优势。文章介绍了该相机的组成、工作原理、相机关键技术及实现情况,给出地面测试与试验结果,并简要介绍在轨测试和应用情况。相机目前在轨稳定运行,性能优异,已获取大量高分辨率热红外影像,可为后续同类载荷研制提供参考。

Object: Thermal infrared images are widely used in the field of land resource management, fire detection and missile warning and surveillance. In order to improve China’s ecological management and strengthen the supervision of high-energy-consuming enterprises such as steel plant, the requirements for the development of a high-resolution, high-sensitivity and large-width space thermal infrared camera is proposed. On this basis, the thermal infrared camera installed on the 5m Optical 02 Satellite was designed and developed. The thermal infrared camera was successfully launched at the Taiyuan Satellite Launch Center on December 26, 2021. Method: The thermal infrared camera adopts an advanced push-broom imaging system, and uses an 8000-pixel long-line array long-wave infrared detector to obtain thermal infrared images in the 7.7μm~10.5μm spectrum. The thermal infrared camera chooses an off-axial three-mirror main optical system and a transmission system with free-form surfaces to achieve 8.6°×1.1°field of view. The absolute distortion of the optical system is less than 1μm, the average MTF is better than 0.32, and the uniformity of the focal plane illumination is better than 0.98. The thermal infrared camera focal plane is composed of eight CCDs. The pixel number of one CCD is 1024×6×2. Time delay and integration technology is used to improve the SNR ratio. The material deformation matching method is used to ensure the thermal stress and displacement meet the requirement at a low temperature of 80K. The thermal infrared camera also uses cryogenic optical technology to reduce the system background noise and improve the dynamic range of the camera. Several lens close to the focal plane work at 200K. The cryogenic lens is cooled by a pulse tube cryocooler. At the same time, a calibration mechanism and focusing mechanism are installed inside the thermal infrared camera, which can realize on-orbit radiation calibration and focal plane adjustment. These designs improve camera radiometric accuracy and reliability. After completing the detailed design, the ground sampling distance of the thermal infrared camera is 15m. The coverage width of the thermal infrared camera is 120km. The NETD of the thermal infrared camera is better than 0.1K@300K. The thermal infrared camera achieves high-resolution, high-sensitivity and large-width observation simultaneously. Result: After the alignment and ground test of the thermal infrared camera, the average MTF of the entire field of view reaches 0.151, the NETD reaches 0.06K@300K, the dynamic range exceeds 240K~340K, the linearity of the radiometric calibration curve is better than 0.99. After the 5m Optical 02 Satellite was launched and the on-orbit test was completed. The image geometric performance and radiation performance on-orbit are excellent, and the resolution and width meet the requirements. By analyzing the image data of high temperature and low temperature ground objects near 300K, the on-orbit NETD is close to 0.08K, and the absolute radiation calibration accuracy on-orbit is better than 1K. Conclusion: Compared with the GF-5 02 VIMS launched in China in 2021 and the Landsat-9 TIRS-2 launched in the United States in 2021, the thermal infrared camera onboard 5m Optical 02 satellite has greatly improved the resolution and maintains a large width. At the same time, the NETD is close to the best in the world. The thermal infrared camera can well support the businesses related to land resources.