TIR remote sensing systems mainly use remote sensing means to sense the thermal infrared radiation difference of ground objects, which can be used to identify ground objects and retrieve surface temperature parameters. TIR remote sensing detecting technology has been widely used in resource investigation, ecological environment monitoring, disaster assessment and military target detection and recognition because of its excellent working ability in bad weather and night. With the deepening of engineering application and scientific research, it is urgent to improve the thermal sensitivity of infrared remote sensors. In the design of TIR remote sensing system, for the application needs of detection capability, the target, background need to consider the three main factors of the system. Noise Equivalent Temperature Difference (NETD) is an important indicator of representing the temperature sensitivity of the remote sensing system. NETD could be affected by the optical system radiation on the TIR remote sensing system.The influence of NETD by optical system radiation could be analyzed by the method of the number of noise electron or by the method of D* of the detector. The noise of the remote sensor system consists of photon noise (scene radiation and the fluctuation of the main background radiation reaching the focal plane), detector assembly noise and circuit noise. Under the condition of fixed imaging spectrum, integral time, detector and video circuit parameters, the cryogenic optical system can reduce its own radiation, reduce the photon noise, and improve the temperature sensitivity of the system. This paper quantified the relationship between optical system radiation and optical path design, operating temperature and the temperature sensitivity of thermal infrared remote sensing camera. The simulation method uses the software TracePro to conduct light tracing, analyzes the irradiance distribution of the optical system and the optical machine structure at the respective working temperature, and finally accumulates all the components to obtain the total radiation amount on the detector. The working temperature of optical system will affect the temperature sensitivity of the system. When the optical system radiation drops to lower than 1/10 of the target signal radiation, it could be regarded as a background-limiting detecting system, where the optical system radiation impact on the temperature sensitivity of the thermal infrared remote sensor can be ignored. In the load design, when the detector type is fixed, the sensitivity of load detection can be improved by reducing the optical system temperature. In order to verify the influence of changing the temperature of the optical system on the temperature sensitivity of the thermal infrared remote sensor, an airborne infrared remote sensor was designed and developed. The working temperature of the optical lens of the infrared remote sensor was changed form 313 K to 293 K, and NETD was tested. With the decrease of optical system temperature, the temperature sensitivity is improved. So the performance improvement was verified by the NETD testing. With the limitation of atmospheric temperature of airborne thermal infrared remote sensor below the dew point, this test did not carry out the performance verification of the temperature below 293 K. NETD test of the remote sensor with the lower temperature work on the deep low temperature working in the vacuum tank will be done in future. The development of this study is important for the design and development of cryogenic optical TIR remote sensing systems.

remote sensing;FIR remote sensing system;detection capability;performance testing;Noise Equivalent Temperature Difference （NETD）