Since 2000

China has launched four sun-synchronous ocean optical remote sensing satellites

namely

HY-1A

HY-1B

HY-1C

and HY-1D. The detection of Sea Surface Temperature (SST) distribution and variation is one of the main tasks of Chinese Ocean Color and Temperature Scanner (COCTS)

which is the main load of HY-1 satellite. The dynamic range of the actual water temperature detection channel is required to cover the temperature range of 200 K to 320 K

considering the detection of sea ice

typhoon

and other meteorological elements over the ocean. The variation of temperature in some ocean areas leads to severe weather disasters. Thus

SST detection channels should satisfy the requirements of detection sensitivity and quantification accuracy.

This study aims to design an information acquisition circuit of infrared channel for COCTS according to the technical requirements

including a pre-amplifier circuit to amplify the weak signal of the detector

AC amplifier

which eliminates the basic level to improve the dynamic range

and the channel amplifier circuit

which can realize the DC recovery and dynamic range adjustment of the signal.

Based on the study of the working mechanism of the photoconductive infrared detector used

and combined with the system composition and the characteristics of COCTS

the form and parameters of each stage amplifier circuit were determined thru theoretical analysis

calculation

and simulation to ensure that the contradictory requirements of high dynamic range and high sensitivity are met at the same time. The corresponding high-pass and low-pass filter are designed to achieve stable reference level detection and single pixel signal detection of the whole field of view. The system performance of COCTS is measured in the vacuum environment simulation laboratory to verify the reasonability of information acquisition circuit design.

Results of the infrared radiometric calibration in the laboratory show that the dynamic range of the two infrared channels covers 177 to 327 K and 173 to 324 K; they satisfy the technical requirements of 200 to 320 K. The Noise Equivalent Temperature Difference (NETD) of the two infrared channels in the whole dynamic range is between 20 and 110 mK. At the appraisal position of 300 K

NETD has reached 21 to 34 mK

which is much better than the technical requirements of 0.2 mK. The space test environment is more complex than the laboratory

and the measuring accuracy has some differences. The results of in orbit test show that the dynamic range of the two infrared channels is 186 to 328 K and 185 to 326 K

and the NETD in the whole dynamic range is between 50 mK and 110 mK

according to the window size of the selected target area. The performance is better than the technical requirements.Conclusion The infrared channel can track the change in the blackbody signal on the satellite with modifications in time and the surrounding environment. Thus

the calibration coefficient of the infrared channel can be corrected in real-time. The expected goal of real-time radiometric calibration in orbit can be achieved. This lays a foundation for the quantitative inversion of SST and can obtain and develop high-quality global SST products.