Solar irradiance monitor（ SIM） operates as a satellite payload

on a sun-synchronous orbit

will experience a shady side and a light side each orbital period. From the shady area to light area

changes in the ambient temperature are intense

while the instrument needs to be in a stable temperature for accurate measurement of solar irradiance. When measured in-orbit

in order to ensure that the instruments work in a normal temperature

design an active thermal control test system for SIM. According to conclusion of thermal analysis

determine temperature measurement points and heating zone of instrument. By using MCU and FPGA as hardware platform

acquisition

processing and analysis work of each temperature measurement point are completed

so as to control heating state of each heating zone and achieve active heating control for all the heating circuits when the instrument in the shady area

and host computer is used for real-time monitoring. Experimental results show that the instrument can be maintained at the target temperature average error less than 0. 1 ℃

in the environment simulating the external thermal flux

through control by active control test system

and the design of this system can meet requirements of active thermal control of SIM.