Development of experimental prototype of the Space Cryogenic Absolute Radiometer

In view of the lack of space radiation benchmark traceable to the international system of units (SI), and the difficulty in establishing and maintaining the on-board traceability chain, we researched on the space cryogenic radiation measurement technology. The experimental prototype of the space cryogenic absolute radiometer was developed. The cage support structure is adopted to reduce the size and mass of the whole machine. The multi temperature zone cold aperture system was optimized to reduce of background radiation power and noise. The two-stage GM cooler is used as cold source, and provides the 20K working environment for the cryogenic absolute radiance detector. The thermal link of single stage heat sink was designed. Through active temperature control, a high stable thermal environment better than 1mk is established for the cryogenic absolute radiation detector. The fast measurement algorithm of the cryogenic electrical substitution measurement was designed, then the measurement period was shortened from 12 minutes to 4 minutes. The experimental results illustrate that: For the input energy of 4-15mw, the thermoelectric repeatability of the cryogenic absolute radiation detector is better than 0.01%. The repeatability of the experimental prototype for milliwatt laser power measurement reached 0.01%. The investigation results provide the thermal and experimental basis for the establishment of space cryogenic radiation benchmark. It is significant to improve the accuracy and long-term stability of earth radiance observation system.