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Abstract In a semi-physical simulation test rig for infrared guidance control systems, a low-temperature nitrogen environment is required to emulate the cold background of space. To ensure that the distortion of the light beam emitted by the infrared target simulator during transmission in nitrogen remains within the permissible range of the experiment, this paper establishes a flexible cold chamber simulation model for a low-temperature nitrogen environment. After experimental verification, the internal temperature distribution of the freezing chamber under various conditions was determined, and its optical transmission performance was subsequently evaluated based on this. Results show that under the rated operating condition, with an inlet velocity of 0.05 m/s and an inlet temperature of 153 K, the temperature standard deviation within the beam is 1.48 K, and the peak-to-valley optical path difference (Rδ) is 1.23 μm. The Strehl ratio (S) was 0.965, indicating a minimal effect of low-temperature nitrogen on optical transmission. Inlet velocity has a more significant influence on optical transmission performance. When the velocity ranges from 0.02 m/s to 0.07 m/s, the Rδ and S vary between 0.47-3.43 μm and 0.845-0.978, respectively. Notably, when the inlet velocity decreases to 0.015 m/s, the S drops to 0.798, resulting in the system degrading into a non-ideal imaging state. Additionally, an increase in position angle caused by the rotation of the upper cryogenic chamber decreases the threshold for temperature standard deviation in ideal imaging systems. Compared to a 0° position angle, this threshold decreases from 3.53 K to 3.23 K.
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Received: 27 August 2025
Published: 13 January 2026
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2025, Vol. 8 
