为了准确测量太阳总量辐射，研制了具备自动跟踪能力的太阳辐照绝对辐射计SIAR-3a。介绍了SIAR-3a的原理，提出了双轴太阳跟踪的控制方法。SIAR-3a采用电来标定待测量的太阳总量辐射，可以在测量太阳总量辐射的同时较为准确地跟踪太阳。标定实验中，SIAR-3a在3σ范围内的相对均方根误差是006%，已经标定到了保存在瑞士达沃斯世界辐射中心的世界辐射基准。太阳辐照实验结果表明，SIAR-3a工作可靠，测量结果准确。

To measure total solar irradiance accurately, the solar irradiance absolute radiometer SIAR-3a with the ability of automatic solar tracking is designed and constructed. The principle and structure of the solar irradiance absolute radiometer SIAR-3a are presented in this paper and its control scheme for automatic double-axis solar tracking is proposed. The solar irradiance absolute radiometer SIAR-3a imposes electricity to calibrate the total solar irradiance, which is able to measure the total solar irradiance and follow the sun simultaneously. In the calibration experiments, the corresponding rms error limit of SIAR-3a amounts to 0.06% at the 3σ level, which has been calibrated to World Radiometric Reference stored in World Radiation Centre(WRC) in Davos, Switzerland. The experiment results indicate that SIAR-3a works reliably and accurately.